The Network Layer is concerned about getting packets from source to destination, no matter how many hops it may take. It’s all about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too many packets?
5.4 Internetworking
Working with multiple networks and protocols in order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
The network layer is responsible for delivering packets from source to destination. It must know the topology of the subnet and choose appropriate paths. When sources and destinations are in different networks, the network layer must deal with these differences. The network layer uses logical addressing that is independent of the underlying physical network. Routing ensures packets are delivered through routers and switches from source to destination across interconnected networks.
The Network Layer is concerned about getting packets from source to destination, no matter how many hops it may take. It’s all about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too many packets?
5.4 Internetworking
Working with multiple networks and protocols in order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
Network layer - design Issues ,Store-and-Forward Packet Switching, Services Provided to the Transport Layer, Which service is the best , Implementation of Service , Implementation of Connectionless Service , Implementation of Connection-Oriented Service
1) Computer networks allow communication and sharing of resources between computer systems and devices through communication channels. There are several types of networks including LANs, WANs, and MANs.
2) For communication between systems, both must agree on a protocol which sets rules for data transmission. The two main protocol stacks are OSI and TCP/IP.
3) The network layer is responsible for delivering packets from source to destination. It uses services from the data link layer and provides services to the transport layer. Common network layer protocols are IP (Internet Protocol) for connectionless service and MPLS for connection-oriented service.
This document provides an overview of key concepts in network layer design, including:
- Store-and-forward packet switching and the services provided to the transport layer.
- Implementation of connectionless and connection-oriented services, and comparison of virtual circuits and datagrams.
- Routing algorithms like shortest path, flooding, distance vector, link state, and hierarchical routing.
- Quality of service techniques including integrated services, differentiated services, and MPLS.
- Internetworking issues such as connecting different networks, concatenated virtual circuits, tunneling, and fragmentation.
- An overview of the network layer in the Internet including IP, addressing, routing protocols like OSPF and BGP, and
The document proposes a solution for interconnecting connectionless and connection-oriented networks that allows gateways to set up connections through the connection-oriented network for certain traffic when data arrives before a connection is established. It describes using routing protocols to share routing information between gateways and holding up packets at the gateway until a connection is set up, either by triggering connection establishment from transport layer headers or using small provisioned connections. The solution aims to take advantage of shorter paths through the connection-oriented network when possible.
1) Computer networks allow computers to communicate and share resources by connecting them through communication channels. There are several types of networks including LANs, WANs, and MANs.
2) For communication between computers on a network, both sides must agree on protocols which are sets of rules that govern data transmission. The two main protocol stacks are OSI and TCP/IP.
3) The network layer is responsible for delivering packets from source to destination by choosing appropriate paths through routers. It provides connectionless and connection-oriented services to the transport layer above it.
The document outlines Chapter 4 of a networking textbook. Chapter 4 covers the network layer, including network layer services, how routers work, routing algorithms, and implementations in the Internet. The key topics covered are virtual circuit versus datagram networks, the functions of routers including forwarding and routing, and routing algorithms like link state and distance vector.
The network layer is responsible for delivering packets from source to destination. It must know the topology of the subnet and choose appropriate paths. When sources and destinations are in different networks, the network layer must deal with these differences. The network layer uses logical addressing that is independent of the underlying physical network. Routing ensures packets are delivered through routers and switches from source to destination across interconnected networks.
The Network Layer is concerned about getting packets from source to destination, no matter how many hops it may take. It’s all about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too many packets?
5.4 Internetworking
Working with multiple networks and protocols in order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
Network layer - design Issues ,Store-and-Forward Packet Switching, Services Provided to the Transport Layer, Which service is the best , Implementation of Service , Implementation of Connectionless Service , Implementation of Connection-Oriented Service
1) Computer networks allow communication and sharing of resources between computer systems and devices through communication channels. There are several types of networks including LANs, WANs, and MANs.
2) For communication between systems, both must agree on a protocol which sets rules for data transmission. The two main protocol stacks are OSI and TCP/IP.
3) The network layer is responsible for delivering packets from source to destination. It uses services from the data link layer and provides services to the transport layer. Common network layer protocols are IP (Internet Protocol) for connectionless service and MPLS for connection-oriented service.
This document provides an overview of key concepts in network layer design, including:
- Store-and-forward packet switching and the services provided to the transport layer.
- Implementation of connectionless and connection-oriented services, and comparison of virtual circuits and datagrams.
- Routing algorithms like shortest path, flooding, distance vector, link state, and hierarchical routing.
- Quality of service techniques including integrated services, differentiated services, and MPLS.
- Internetworking issues such as connecting different networks, concatenated virtual circuits, tunneling, and fragmentation.
- An overview of the network layer in the Internet including IP, addressing, routing protocols like OSPF and BGP, and
The document proposes a solution for interconnecting connectionless and connection-oriented networks that allows gateways to set up connections through the connection-oriented network for certain traffic when data arrives before a connection is established. It describes using routing protocols to share routing information between gateways and holding up packets at the gateway until a connection is set up, either by triggering connection establishment from transport layer headers or using small provisioned connections. The solution aims to take advantage of shorter paths through the connection-oriented network when possible.
1) Computer networks allow computers to communicate and share resources by connecting them through communication channels. There are several types of networks including LANs, WANs, and MANs.
2) For communication between computers on a network, both sides must agree on protocols which are sets of rules that govern data transmission. The two main protocol stacks are OSI and TCP/IP.
3) The network layer is responsible for delivering packets from source to destination by choosing appropriate paths through routers. It provides connectionless and connection-oriented services to the transport layer above it.
The document outlines Chapter 4 of a networking textbook. Chapter 4 covers the network layer, including network layer services, how routers work, routing algorithms, and implementations in the Internet. The key topics covered are virtual circuit versus datagram networks, the functions of routers including forwarding and routing, and routing algorithms like link state and distance vector.
The document discusses network layer design issues related to connectionless and connection-oriented services. Connectionless services route each packet independently, while connection-oriented services establish a logical connection and route all traffic for that connection along the same path. Virtual circuits use connection-oriented services, pre-determining the route and maintaining state information for each connection. Datagram subnets are connectionless, routing each packet independently without state information. Virtual circuits provide easier quality of service and congestion control while datagram subnets are more robust to router failures.
The network layer is responsible for routing packets from source to destination using a routing algorithm. The routing algorithm must deal with issues of correctness, stability, fairness, and optimality. The network layer also handles congestion when more packets enter an area than can be processed. When connecting different network technologies, the same problems are present but are worse as packets may travel through many different networks with different formats and technologies.
The document discusses network layer design issues and protocols. It covers store-and-forward packet switching, the functions of the network layer including routing and congestion control. It then describes the implementation of connectionless and connection-oriented services, comparing virtual circuits and datagrams. Various routing algorithms are also summarized, such as shortest path, flooding, distance vector, and link state routing.
1) In a connectionless datagram subnet, packets are routed independently without establishing a connection. Routers break messages into packets that are forwarded based on internal routing tables.
2) In a connection-oriented virtual circuit subnet, a connection path must be established before packets can be sent. Each packet carries an identifier of its virtual circuit. Routers replace circuit identifiers to avoid conflicts at downstream routers.
3) Both approaches were compared, noting that connectionless datagrams require no setup but have independent routing, while virtual circuits require setup but can forward all packets along the same pre-established path.
This document provides an overview of the network layer and some of its key protocols. It begins with an introduction to the network layer and its main responsibilities, including routing packets between subnets that may have different addressing schemes or protocols. It then discusses some of the network layer's main functionalities and features. The remainder of the document defines and describes several important network layer protocols, including EIGRP, ICMP, IGMP, IPv4, and others. It provides high-level explanations of how these protocols function and their roles within the network layer.
The document outlines the key concepts in the network layer chapter, including:
- The functions of the network layer including forwarding, routing, and connection setup in some architectures.
- The differences between virtual circuit and datagram networks and how routers and forwarding work differently in each.
- An overview of the main components and functions of a router, including routing processors, switching fabrics, input/output ports, and forwarding tables.
- Details on IP as the main network layer protocol used in the Internet, including its datagram format, addressing, and fragmentation.
The document discusses key concepts about the network layer, including:
1) The network layer is responsible for transporting data segments from the sending host to the receiving host by encapsulating segments into datagrams. Network layer protocols exist in every host and router.
2) The main functions of the network layer are forwarding, which moves packets through routers from input to output, and routing, which determines the best path from source to destination using routing algorithms.
3) Network layers can provide either a connection-oriented service using virtual circuits, which require call setup, or a connectionless service using datagrams as in the Internet protocol.
The document discusses various layers and concepts in computer networks and internetworking. It covers the network layer and its responsibilities in delivering packets from source to destination. It then discusses services provided by the network layer to the transport layer, including connection-oriented and connectionless services. Various routing algorithms and concepts are covered such as distance vector routing, link state routing, hierarchical routing, flooding, shortest path algorithms, broadcast routing, and multicast routing.
The document discusses the network layer and routing. It begins by stating the goals of understanding network layer services like routing, dealing with scale, and router functionality. It then provides an overview of network layer services, routing principles, hierarchical routing, IP, routing protocols, and functions of routers. The key abstraction provided by the network layer is the service model, which can be either virtual circuits or datagrams. Routing determines the path between source and destination, and algorithms like Dijkstra's algorithm are used to find the least cost path through a graph of routers and links.
Computer Networks Unit 2 UNIT II DATA-LINK LAYER & MEDIA ACCESSDr. SELVAGANESAN S
The document discusses data link layer framing and protocols. It describes:
1) Two main approaches to framing - byte-oriented (using sentinel characters) and bit-oriented (using bit stuffing). Protocols discussed include BISYNC, DDCMP, and HDLC.
2) Features of PPP framing including negotiated field sizes and use of LCP control messages.
3) Functions of data link layer including framing, flow control, error control, and media access control. The relationship between the logical link control and media access control sublayers is also covered.
Transport layer is responsible for the overall end-to-end transfer of application data.
Because different applications have different requirements, there are multiple Transport layer protocols.
Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
TCP and UDP headers.
Port Addressing, socket pair.
Types of port numbers: Well Known Ports (0 to 1023), Registered Ports (1024 to 49151) and Dynamic or Private ‘Ephemeral’ Ports (49152 to 65535).
Netstat command : examines the open connections on a host.
Transport Layer Functions.
TCP Connection Establishment (3-way handshake).
Connection Management - Flow Control through buffering, congestion avoidance, and windowing.
Flow Control – Reducing the window size .
TCP Connection Termination (4-way Handshake).
This document provides an overview of various topics related to the network layer, including IPv4, IPv6, ARP, RARP, mobile IP, routing algorithms, and routing protocols. It begins with basics of IPv4 such as its addressing scheme and role in interconnecting networks. IPv6 is then introduced, along with reasons for its development and key features like its large 128-bit addresses. Address Resolution Protocol (ARP) and Reverse ARP (RARP) are also covered. The document concludes by discussing routing algorithms like link-state and distance-vector, as well as protocols including RIP, OSPF, and BGP.
Packet switching approaches include datagram and virtual-circuit approaches. The virtual-circuit approach involves three phases: setup, data transfer, and teardown. During setup, routers create entries for a virtual circuit based on request and acknowledgment packets exchanged. This establishes a defined path for network-layer packets to follow, identified by a flow label. Once the virtual circuit is set up, packets can be forwarded independently based only on the flow label. Finally, teardown packets remove the entries from router tables once transfer is complete.
The document provides an overview of concepts related to the data link layer. It discusses functions of the data link layer including framing, flow control, and error detection. It also covers topics such as HDLC, PPP, channel allocation problems, multiple access protocols including ALOHA, CSMA, CSMA/CD, and channelization techniques like FDMA, TDMA, and CDMA. Specific standards for wired LANs like Ethernet and wireless LANs like IEEE 802.11 are also mentioned. Finally, it briefly discusses technologies like token bus, token ring, and virtual LANs.
This document provides an overview of key concepts in network layer delivery, forwarding, and routing. It discusses delivery and forwarding of packets, including direct vs indirect delivery and next-hop vs route forwarding methods. It also summarizes several unicast routing protocols, including distance vector protocols like RIP and link state protocols like OSPF. Finally, it discusses path vector routing and Border Gateway Protocol (BGP) for interdomain routing.
The document discusses computer networks and media access control. It covers topics like Ethernet, wireless LANs, Bluetooth, Wi-Fi, switching, bridging, IP, and more. The key points are:
1. It provides an overview of the topics to be discussed, including media access control, Ethernet standards, wireless technologies, and internetworking basics.
2. It summarizes the evolution of Ethernet and discusses its physical properties, frame format, addressing, and transmitter algorithm using CSMA/CD.
3. It describes wireless LAN standards like Bluetooth and Wi-Fi, addressing problems in wireless networks, and discussing concepts like spread spectrum, CSMA/CA, and network architectures.
The document is a paper on the network layer written by Muhammad Adil Raja. It begins with an introduction that defines the key functions of the network layer, including getting packets from source to destination across multiple hops. It then outlines the topics to be covered, which are network layer design issues, routing algorithms, congestion control algorithms, and references. The body of the document discusses these topics in more detail through several sections. It covers issues like whether the network layer should provide connection-oriented or connectionless service, and compares virtual circuit and datagram networks. It also examines routing algorithms and the optimality principle.
This document discusses several key design issues that occur across multiple layers in computer networks, including addressing, error control, flow control, multiplexing, and routing. Addressing refers to the need for each layer to identify senders and receivers. Error control handles imperfect physical circuits using error detection and correction codes agreed upon by both ends. Flow control deals with assembling and reassembling messages as they are transmitted. Routing selects a path when multiple options exist between source and destination. Multiplexing and demultiplexing improve network systems by combining and separating multiple communication signals.
This document discusses congestion control and internetworking at the network layer. It begins by defining congestion and the factors that can cause it. It then covers general principles of congestion control such as increasing resources or decreasing traffic. The document discusses congestion control techniques for virtual circuit and datagram subnets, including admission control and choke packets. It also covers internetworking concepts like concatenated virtual circuits, connectionless internetworking, tunneling, and fragmentation.
Computer network components include both hardware and software. The key hardware components are servers, clients, transmission media like cables, and connecting devices like switches and routers. Servers store and manage network resources, clients access these resources, and connecting devices allow communication across networks. Important software includes network operating systems and protocols that allow devices to communicate according to standard rules. Understanding the roles of these various components is essential for setting up both small home networks and larger organization networks.
The document discusses network layer design issues related to connectionless and connection-oriented services. Connectionless services route each packet independently, while connection-oriented services establish a logical connection and route all traffic for that connection along the same path. Virtual circuits use connection-oriented services, pre-determining the route and maintaining state information for each connection. Datagram subnets are connectionless, routing each packet independently without state information. Virtual circuits provide easier quality of service and congestion control while datagram subnets are more robust to router failures.
The network layer is responsible for routing packets from source to destination using a routing algorithm. The routing algorithm must deal with issues of correctness, stability, fairness, and optimality. The network layer also handles congestion when more packets enter an area than can be processed. When connecting different network technologies, the same problems are present but are worse as packets may travel through many different networks with different formats and technologies.
The document discusses network layer design issues and protocols. It covers store-and-forward packet switching, the functions of the network layer including routing and congestion control. It then describes the implementation of connectionless and connection-oriented services, comparing virtual circuits and datagrams. Various routing algorithms are also summarized, such as shortest path, flooding, distance vector, and link state routing.
1) In a connectionless datagram subnet, packets are routed independently without establishing a connection. Routers break messages into packets that are forwarded based on internal routing tables.
2) In a connection-oriented virtual circuit subnet, a connection path must be established before packets can be sent. Each packet carries an identifier of its virtual circuit. Routers replace circuit identifiers to avoid conflicts at downstream routers.
3) Both approaches were compared, noting that connectionless datagrams require no setup but have independent routing, while virtual circuits require setup but can forward all packets along the same pre-established path.
This document provides an overview of the network layer and some of its key protocols. It begins with an introduction to the network layer and its main responsibilities, including routing packets between subnets that may have different addressing schemes or protocols. It then discusses some of the network layer's main functionalities and features. The remainder of the document defines and describes several important network layer protocols, including EIGRP, ICMP, IGMP, IPv4, and others. It provides high-level explanations of how these protocols function and their roles within the network layer.
The document outlines the key concepts in the network layer chapter, including:
- The functions of the network layer including forwarding, routing, and connection setup in some architectures.
- The differences between virtual circuit and datagram networks and how routers and forwarding work differently in each.
- An overview of the main components and functions of a router, including routing processors, switching fabrics, input/output ports, and forwarding tables.
- Details on IP as the main network layer protocol used in the Internet, including its datagram format, addressing, and fragmentation.
The document discusses key concepts about the network layer, including:
1) The network layer is responsible for transporting data segments from the sending host to the receiving host by encapsulating segments into datagrams. Network layer protocols exist in every host and router.
2) The main functions of the network layer are forwarding, which moves packets through routers from input to output, and routing, which determines the best path from source to destination using routing algorithms.
3) Network layers can provide either a connection-oriented service using virtual circuits, which require call setup, or a connectionless service using datagrams as in the Internet protocol.
The document discusses various layers and concepts in computer networks and internetworking. It covers the network layer and its responsibilities in delivering packets from source to destination. It then discusses services provided by the network layer to the transport layer, including connection-oriented and connectionless services. Various routing algorithms and concepts are covered such as distance vector routing, link state routing, hierarchical routing, flooding, shortest path algorithms, broadcast routing, and multicast routing.
The document discusses the network layer and routing. It begins by stating the goals of understanding network layer services like routing, dealing with scale, and router functionality. It then provides an overview of network layer services, routing principles, hierarchical routing, IP, routing protocols, and functions of routers. The key abstraction provided by the network layer is the service model, which can be either virtual circuits or datagrams. Routing determines the path between source and destination, and algorithms like Dijkstra's algorithm are used to find the least cost path through a graph of routers and links.
Computer Networks Unit 2 UNIT II DATA-LINK LAYER & MEDIA ACCESSDr. SELVAGANESAN S
The document discusses data link layer framing and protocols. It describes:
1) Two main approaches to framing - byte-oriented (using sentinel characters) and bit-oriented (using bit stuffing). Protocols discussed include BISYNC, DDCMP, and HDLC.
2) Features of PPP framing including negotiated field sizes and use of LCP control messages.
3) Functions of data link layer including framing, flow control, error control, and media access control. The relationship between the logical link control and media access control sublayers is also covered.
Transport layer is responsible for the overall end-to-end transfer of application data.
Because different applications have different requirements, there are multiple Transport layer protocols.
Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
TCP and UDP headers.
Port Addressing, socket pair.
Types of port numbers: Well Known Ports (0 to 1023), Registered Ports (1024 to 49151) and Dynamic or Private ‘Ephemeral’ Ports (49152 to 65535).
Netstat command : examines the open connections on a host.
Transport Layer Functions.
TCP Connection Establishment (3-way handshake).
Connection Management - Flow Control through buffering, congestion avoidance, and windowing.
Flow Control – Reducing the window size .
TCP Connection Termination (4-way Handshake).
This document provides an overview of various topics related to the network layer, including IPv4, IPv6, ARP, RARP, mobile IP, routing algorithms, and routing protocols. It begins with basics of IPv4 such as its addressing scheme and role in interconnecting networks. IPv6 is then introduced, along with reasons for its development and key features like its large 128-bit addresses. Address Resolution Protocol (ARP) and Reverse ARP (RARP) are also covered. The document concludes by discussing routing algorithms like link-state and distance-vector, as well as protocols including RIP, OSPF, and BGP.
Packet switching approaches include datagram and virtual-circuit approaches. The virtual-circuit approach involves three phases: setup, data transfer, and teardown. During setup, routers create entries for a virtual circuit based on request and acknowledgment packets exchanged. This establishes a defined path for network-layer packets to follow, identified by a flow label. Once the virtual circuit is set up, packets can be forwarded independently based only on the flow label. Finally, teardown packets remove the entries from router tables once transfer is complete.
The document provides an overview of concepts related to the data link layer. It discusses functions of the data link layer including framing, flow control, and error detection. It also covers topics such as HDLC, PPP, channel allocation problems, multiple access protocols including ALOHA, CSMA, CSMA/CD, and channelization techniques like FDMA, TDMA, and CDMA. Specific standards for wired LANs like Ethernet and wireless LANs like IEEE 802.11 are also mentioned. Finally, it briefly discusses technologies like token bus, token ring, and virtual LANs.
This document provides an overview of key concepts in network layer delivery, forwarding, and routing. It discusses delivery and forwarding of packets, including direct vs indirect delivery and next-hop vs route forwarding methods. It also summarizes several unicast routing protocols, including distance vector protocols like RIP and link state protocols like OSPF. Finally, it discusses path vector routing and Border Gateway Protocol (BGP) for interdomain routing.
The document discusses computer networks and media access control. It covers topics like Ethernet, wireless LANs, Bluetooth, Wi-Fi, switching, bridging, IP, and more. The key points are:
1. It provides an overview of the topics to be discussed, including media access control, Ethernet standards, wireless technologies, and internetworking basics.
2. It summarizes the evolution of Ethernet and discusses its physical properties, frame format, addressing, and transmitter algorithm using CSMA/CD.
3. It describes wireless LAN standards like Bluetooth and Wi-Fi, addressing problems in wireless networks, and discussing concepts like spread spectrum, CSMA/CA, and network architectures.
The document is a paper on the network layer written by Muhammad Adil Raja. It begins with an introduction that defines the key functions of the network layer, including getting packets from source to destination across multiple hops. It then outlines the topics to be covered, which are network layer design issues, routing algorithms, congestion control algorithms, and references. The body of the document discusses these topics in more detail through several sections. It covers issues like whether the network layer should provide connection-oriented or connectionless service, and compares virtual circuit and datagram networks. It also examines routing algorithms and the optimality principle.
This document discusses several key design issues that occur across multiple layers in computer networks, including addressing, error control, flow control, multiplexing, and routing. Addressing refers to the need for each layer to identify senders and receivers. Error control handles imperfect physical circuits using error detection and correction codes agreed upon by both ends. Flow control deals with assembling and reassembling messages as they are transmitted. Routing selects a path when multiple options exist between source and destination. Multiplexing and demultiplexing improve network systems by combining and separating multiple communication signals.
This document discusses congestion control and internetworking at the network layer. It begins by defining congestion and the factors that can cause it. It then covers general principles of congestion control such as increasing resources or decreasing traffic. The document discusses congestion control techniques for virtual circuit and datagram subnets, including admission control and choke packets. It also covers internetworking concepts like concatenated virtual circuits, connectionless internetworking, tunneling, and fragmentation.
Computer network components include both hardware and software. The key hardware components are servers, clients, transmission media like cables, and connecting devices like switches and routers. Servers store and manage network resources, clients access these resources, and connecting devices allow communication across networks. Important software includes network operating systems and protocols that allow devices to communicate according to standard rules. Understanding the roles of these various components is essential for setting up both small home networks and larger organization networks.
Multiprocessor mesh interconnection networks are 2-dimensional networks, with the processors arranged at the nodes of a grid, and point-to-point links connecting each node to its neighbors.
This lab manual provides instructions for a Computer Network lab course. The course aims to provide hands-on networking experience. Students will experiment with networking topics like IP addressing, routing protocols, and network troubleshooting using tools like ping and traceroute. Students will also learn network modeling and simulation using software like Packet Tracer. The manual outlines 9 experiments that cover topics such as network cabling, network devices, IP configuration, basic network commands, and configuring network topologies in Packet Tracer using different routing protocols.
This lab manual provides instructions for a Computer Network lab course. The course aims to provide hands-on networking experience. Students will experiment with networking topics like IP addressing, routing protocols, and network troubleshooting using tools like ping and traceroute. Students will also learn about network modeling and simulation using software like Packet Tracer. The manual outlines 9 experiments that involve studying network devices, IP addressing, connecting computers to a LAN, networking commands, and configuring network topologies using Packet Tracer.
manual on networking cabling with pratical guideNuhuSamaila
1. Configure the IP addresses of the client computers to be in the same subnet as the host computer sharing the internet connection. 2. Use ping and tracert commands on the client computers to test connectivity to the host and internet gateway. 3. Use ipconfig to view and confirm TCP/IP settings like IP addresses, subnet masks, and default gateways on all computers match the LAN configuration.
Students will first study basic networking commands like ping and tracert using Command Prompt to test network connectivity. They will then configure the network settings of both a host computer and client computers to share an internet connection on the LAN. The host will be configured to act as a DHCP server to automatically assign IP addresses to connected clients. Students will use networking configuration commands to set the host IP as 192.168.0.1 and enable internet connection sharing.
This document provides an overview of the syllabus for the Computer Networks course CS 6551. It begins with introducing the fundamentals of computer networks including characteristics, components, and transmission modes. It then discusses building a network based on requirements and different network architectures like OSI and TCP/IP models. The document covers various link layer services such as framing, flow control, and error detection. It also discusses concepts related to network performance like bandwidth, throughput, latency, and bandwidth-delay product.
A computer network is network of computer .It connects multiple computer in manner to enable meaningful transmission and exchange of data among them.Main objective of CN is sharing of information ,resources and processing load among the connected computer.
you can easily get basic introduction of COMPUTER NETWORK
Computer networks allow interconnected computers to work together. They can be used for business applications using a client-server model, home networking, by mobile users, and raise social issues. The document discusses different types of network hardware including local area networks (LANs), metropolitan area networks (MANs), wide area networks (WANs), wireless networks, home networks, and internetworks. It also covers network software including protocol hierarchies, connection-oriented vs. connectionless services, service primitives, and the relationship between services and protocols.
The document describes the design and implementation of an on-chip system-on-chip (SOC) interconnect using an i-SLIP scheduling algorithm. The interconnect uses a crossbar switch architecture to connect 8 devices on the chip. Each device has an input and output block that can store up to 32 packets to send and receive. The scheduler block implements the i-SLIP algorithm to determine which packets from the input blocks will be sent to the output blocks. The goal is to provide an efficient communication mechanism between the on-chip devices using a packet-based protocol over the interconnect.
1.NggggggggggghhhhhhhhhhS UNIT - 1.pptx.pdfsadoyah492
The document discusses various networking devices and network layer attacks. It begins by defining networking devices that operate at different layers, such as network interface cards, routers, switches, hubs, bridges, and gateways. It then covers different types of network layer attacks like IP spoofing, hijacking, Smurf attacks, wormhole attacks, and others. The document provides details on each attack method, how they are carried out, and their impact on network communication.
Chapter 8 the role of networking in manufacturingN. A. Sutisna
This document discusses data communication and networking in manufacturing systems. It covers local area network concepts like topologies, protocols, and addressing. The most common high-level network topologies for manufacturing are bus structures and star networks. Bus networks offer flexibility in cable utilization but contention is an issue. Ring and star networks are also discussed along with techniques for resolving contention like CSMA/CD and token passing.
This document discusses internetworking and the key concepts involved. It explains that an internetwork allows different networks to communicate by connecting them through intermediate systems like routers and bridges. There are two main architectural approaches for building an internetwork - connection-oriented which establishes virtual circuits, and connectionless which treats each packet independently. Connectionless is preferred and uses the Internet Protocol (IP). The document outlines the requirements, components, and operation of a connectionless internetwork. It also discusses important design issues like routing, datagram lifetime, fragmentation, error control, and flow control.
This document provides an overview of computer networks, including definitions, components, models, and transmission modes. It defines a computer network as a group of connected devices that share communication channels and resources. The key points are:
- Computer networks use protocols to organize traffic transmitted over wired or wireless pathways between devices.
- The two main network technologies are peer-to-peer and client-server models. Client-server has dedicated servers and clients, while peer-to-peer allows any device to serve or request resources.
- Network topologies include bus, ring, star, mesh, tree and hybrid configurations. Transmission modes are simplex, half-duplex and full-duplex.
Chapter 2. vantage understanding sensor placement in networksPhu Nguyen
This document provides an overview of network layering and how it impacts network vantage for sensor placement and data collection. It discusses the OSI 7-layer model and TCP/IP 4-layer model and how sensors can monitor different layers. It describes how vantage is determined at the physical layer through collision domains, at the data link layer through switches, and how routing impacts vantage at the network layer. It also covers the different addressing schemes used at each layer including MAC addresses, IPv4 addresses, and how protocols like ARP are used to map between them.
This document discusses network architectures and protocols. It describes the OSI 7-layer model and the TCP/IP model. The key layers of each model are presented, including their functions and example protocols. Encapsulation is defined as the process of adding header and trailer data to messages at each layer. This allows protocols to communicate indirectly through lower level protocols in the protocol graph.
The document discusses the Transparent Interconnection of Lots of Links (TRILL) protocol. It begins by describing some problems with the existing Spanning Tree Protocol (STP), such as inefficient paths, underutilized bandwidth, lack of multipath forwarding, and slow convergence. It then introduces TRILL as a solution, which uses routing bridges and IS-IS routing to calculate optimal layer 2 paths. Key benefits of TRILL include shortest path forwarding, multipath forwarding for better bandwidth utilization, reduced forwarding table sizes, loop mitigation, and VLAN support. TRILL headers are also described.
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Gen Z and the marketplaces - let's translate their needsLaura Szabó
The product workshop focused on exploring the requirements of Generation Z in relation to marketplace dynamics. We delved into their specific needs, examined the specifics in their shopping preferences, and analyzed their preferred methods for accessing information and making purchases within a marketplace. Through the study of real-life cases , we tried to gain valuable insights into enhancing the marketplace experience for Generation Z.
The workshop was held on the DMA Conference in Vienna June 2024.
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HijackLoader Evolution: Interactive Process HollowingDonato Onofri
CrowdStrike researchers have identified a HijackLoader (aka IDAT Loader) sample that employs sophisticated evasion techniques to enhance the complexity of the threat. HijackLoader, an increasingly popular tool among adversaries for deploying additional payloads and tooling, continues to evolve as its developers experiment and enhance its capabilities.
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2. Chap. 5- Net2 2
Chapter Overview
The Network Layer is concerned about getting
packets from source to destination, no
matter how many hops it may take. It’s all
about routing.
5.1 Network Layer Design Issues
What do we need to think about in this layer?
5.2 Routing Algorithms
Strategies for getting from source to
destination.
5.3 Congestion Control Algorithms
How do we keep from bottlenecking from too
many packets?
5.4 Internetworking
Working with multiple networks and protocols in
order to deliver packets.
5.5 The Network Layer in the Internet
Gluing together a collection of subnets.
3. Chap. 5- Net2 3
Internetworking
Overview
Getting various networks to all play together.
Problems occur because:
1. Companies don’t have cohesive policies for
networking.
2. New technology replaces some of the old
technology.
5.1 Network Layer Design Issues
5.2 Routing Algorithms
5.3 Congestion Control
Algorithms
5.4 Internetworking
5.5 The Network Layer in the
Internet
4. Chap. 5- Net2 4
Internetworking Overview
Reminder: The Internet is a homogeneous collection of networks,
all using TCP/IP and associated protocols. The internet, the
more generic term, is made up of a hodgepodge of different
hardware and protocols.
Multiple networks and multiple network types are a fact of life:
There are a number of reasons for this:
• Growth: Individual departments in a university buy LANs for
their own machines and eventually want to interconnect with
other campus LANs.
• Fault isolation, geography, and security: Even when feasible to
use one network, an organization can obtain exclusive control
over a single local network.
• Control: Some organizations want to be able to say what
happens on their network.
• Modernization: As new technology appears, some
organizations replace their networks while other’s don't.
5. Chap. 5- Net2 5
Internetworking Overview
An example of mixing together multiple types of networks.
6. Chap. 5- Net2 6
Internetworking Overview
Internetworking deals with the issues of interconnecting multiple networks. Physical networks can be
connected at several levels:
1. Repeaters operate at the physical layer (layer 1), copying signals from one LAN to another. They
operate at the bit level, and have no notion of what the bits (or even frames!) mean.
2. Bridges operate at the data link layer (layer 2), copying frames from one LAN to another.
a. They perform store-and-forward packet switching, but use only level-2 (e.g. frame fields)
information.
b. We've talked about these before in regard to the MAC layer, where we looked at spanning
tree and source routing methods.
3. Routers operate at the network layer (level 3).
a. Similar to bridges in concept.
b. At the network layer, they are fully aware of different network technologies, and can problems
as interconnect different between them.
4. Transport gateways connect two networks at the transport layer (level 4).
5. Application gateways operate at higher levels (level “7”). Application gateways can translate
between OSI mail and SMTP (Internet) mail formats, for instance.
7. Chap. 5- Net2 7
Internetworking Overview
Router Ownership
One issue that arises with Routers is who owns them.
1. Typically, bridges connect LANs of one organization, and so ownership is not an
issue.
2. The ownership question is important for routers because someone has to be
responsible for the router's operation and dual ownership frequently leads to finger
pointing when something goes wrong.
3. One solution is to use half gateways.
• If two countries are involved, for instance, each country owns its half of the router,
with a wire separating the two.
• A special protocol operates over the wire, and each half of the router is
responsible for implementing the protocol.
• For example, the CCITT X.75 standard is used to connect half gateways in
connection-oriented networks.
The reality isn't so simply layered - many products combine bridge and router functionality.
8. Chap. 5- Net2 8
Internetworking How Networks Differ
We've looked at some of these properties before, but here are a list of differences:
Item Some Possibilities
Service Offered Connection-oriented versus connectionless
Protocols IP, IPX, CLNP, Appletalk, DecNet, . . . .
Addressing Flat (802) versus hierarchical (IP)
Multicasting Present or absent (also broadcasting)
Packet Size Every network has its own max
Quality of Service May be present or absent - many different kinds
Error Handling Reliable, ordered, and unordered delivery
Flow control Sliding window, rate control, other, none
Congestion Control Leaky bucket, choke packets, etc.
Security Privacy rules, encryption, etc.
Parameters Different timeouts, flow specs, etc.
Accounting By connect time, by packet, by byte, or none
9. Chap. 5- Net2 9
Internetworking Multiprotocol Routers
Can use "routers" and "gateways" interchangeably or think of routers as within a subnet (same network)
versus gateways (between subnets).
Text calls gateways multi-protocol routers.
Protocol Routers are packet switches that operate at the network layer (level 3). Operating at the
network level gives routers increased flexibility compared to bridges in terms of:
1. Translating addresses between dissimilar networks.
2. Fragmenting large packets for transmission across networks that carry only small maximum
packet lengths.
3. Selecting an appropriate path through the subnet.
4. Enforcing policies (e.g., don't forward any local packets off of this network).
Because routers do more work than bridges, they generally run slower than bridges.
10. Chap. 5- Net2 10
Internetworking Concatenated Virtual Circuits
Internetworking in a connection-oriented environment operates essentially as in the single network case:
1. The sending host opens a virtual circuit as before, but now a circuit goes through router hops.
2. Any two neighboring routers at the internetworking level must be connected to a common
network.
3. Regular router-based virtual circuits connect neighboring routers on the same physical network.
4. The end-to-end virtual circuit is a concatenation of individual virtual circuits through each of the
networks along the path.
So each gateway/router maintains tables for each of the connections passing through it - what
router to pass the packet on to, and an identifier for the virtual circuit.
11. Chap. 5- Net2 11
Internetworking Connectionless Internetworking
Connectionless internets operate just as connectionless networks.
• A host sends a packet to a neighboring router, which forwards it the next router, and so forth.
• Just as with connectionless networks, routers make only a best-effort attempt at delivering the packet.
Datagrams
The Network layer puts datagrams on the subnet. See Figure 5.37
Issues that must be dealt with:
• Networks with different networks protocols are tough to translate between. This is rarely attempted.
(See tunneling below.)
• Addressing - when adjacent networks have differing address schemes, the going gets tough. Again,
problems are generally insurmountable.
12. Chap. 5- Net2 12
Internetworking Connectionless Internetworking
Model Advantages Disadvantages
Virtual Circuit • Buffers can be reserved in advance
• Sequencing guaranteed
• No delayed/duplicate packets
• Table space required
• Can't avoid congestion
• Vulnerable to failures
• Impossible to implement if intervening
network is unreliable
Datagrams • Can adapt to congestion
• Can handle router failures
• None of intervening networks need
to be virtual circuits.
• Susceptible to congestion
13. Chap. 5- Net2 13
Internetworking Tunneling
Tunneling is a special case between two same-type networks across intervening foreign
network(s).
• The whole packet is encapsulated in the protocol of the foreign network to be crossed,
and then restored on the other side. See Figure 5.38
• This avoids, totally, trying to translate the packet.
14. Chap. 5- Net2 14
Internetworking Fragmentation
How to cross networks whose maximum transmission unit (MTU) is smaller than the packet being
transmitted.
1. Connection-oriented internets avoid this problem.
a. By selecting a maximum packet size at connection set up time.
b. That maximum is just min( MTU1, MTU2, ...) of the MTUs in the intervening network.
c. Once the connection is established, the path never changes, so the sender can select a
packet size and never again worry that it will be too large.
2. In connectionless internets, the appropriate packet size depends on the path used.
a. Thus, it can change at any time.
In the general case, setting a minimum MTU for all networks is impractical. A minimum MTU would of
necessity be small, yet sending larger packets should be encouraged for efficiency reasons.
Solutions:
1. Have router drop packets that are too large to send across a network and return an error
message to the sender. The sending host could then retransmit the data in a smaller packet.
2. Have router fragment large packets into several fragments, each small enough to traverse the
network. There are two flavors called Transparent and non-Transparent Fragmentation.
15. Chap. 5- Net2 15
Internetworking Fragmentation
Transparent Fragmentation
With transparent fragmentation, end hosts (sender and receiver) are unaware that fragmentation has
taken place.
A router fragments a packet, and the next-hop router on the same network reassembles the fragments
back into the original packet.
Drawbacks are:
1. All fragments must travel through to the same router. They must all be reassembled by the same
next-hop router
2. Routers must be careful to avoid re-assembly lockup. (The deadlock problem discussed earlier,
where a router has used up all of its buffer space to hold fragments and can no longer accept
new ones).
3. Reassembling fragments uses precious router resources that could otherwise be used
forwarding packets).
4. May fragment/re-assemble several times along the route!
16. Chap. 5- Net2 16
Internetworking Fragmentation
Non-Transparent Fragmentation:
As before, routers fragment packets when needed. Routers along the path do not reassemble.
Destination hosts perform re-assembly (if needed).
Downsides are:
1. Now every host must be prepared to do this job.
2. Overhead of carrying along small segments lasts until destination.
Problems Associated With Fragmentation in General:
1. Fragmenting increases waste: the sum of the bits of the individual fragments exceeds the
number of bits in the original message.
2. Loss of a single fragment requires an end-to-end retransmission; the loss of a single fragment
has the same effect as losing the entire packet.
3. More work to forward three small packets than one large one. The cost of forwarding packets
includes a fixed per-packet cost, that includes doing the route lookup, fielding interrupts, etc.
17. Chap. 5- Net2 17
Internetworking Firewalls
Require all network traffic to/from organization to go through a single point (firewall). The firewall has:
1. Packet filters
2. Application Gateway
3. Proxy Server
Packet Filters:
A router that inspects packets according to a set of rules. Rules generally consist of tables detailing what:
• remote machines can be communicated with.
• ports can be accessed.
Since functionality is associated with ports, incoming requests to port 79 (Finger) could be blocked.
Users could be prevented from telneting into the company, instead going through a modem with additional
password protection.
18. Chap. 5- Net2 18
Internetworking Firewalls
Application Gateway:
Actually looks at content - mail handler might reject spams, very large messages, “lurid” words, etc.
Editorial: If you allow the Internet on your site, you have only modest hope of real security.
Proxy Server:
• Works as an intermediary between a browser and an database/FTP/etc. server.
• This Proxy Server translates between HTTP and FTP for instance.
• Keeps browser from having to know many protocols.
• Can cache previously requested pages.
Within a firewall:
• A local browser talks to the local proxy server (within the firewall.)
• That Proxy contacts remote sites and fetches pages.
• This fetching can be selective (protecting schoolkids, etc.)
19. Chap. 5- Net2 19
Network Layer In
The Internet
Overview
This section is TCP specific
It’s how the Internet works.
Defined by RFC 791.
Most Popular Layer 3.
5.1 Network Layer Design Issues
5.2 Routing Algorithms
5.3 Congestion Control
Algorithms
5.4 Internetworking
5.5 The Network Layer in the
Internet
20. Chap. 5- Net2 20
Network Layer In
The Internet
The IP Protocol
The Internet protocol suite covers (mostly) layers 3, 4, and 5, where ‘layer 5' means
everything in OSI layers 5-7.
At the physical and datalink layers, the TCP/IP protocols don't define any standards.
The protocols have been designed to operate over a large number of layer 2 protocols.
The Internet Protocol (IP) is a network layer protocol.
a. Hosts and gateways process packets called Internet datagrams (IP datagrams).
b. IP provides connectionless, best-effort delivery service to the layers above it.
The Transmission Control Protocol (TCP) is a transport layer protocol.
a. Provides reliable stream service between processes on two machines.
b. It is a sliding window protocol that uses acknowledgments and retransmissions to
overcome the unreliability of IP.
The Universal Datagram Protocol (UDP) is a Transport Layer Protocol.
a. It provides connectionless datagram service between processes.
21. Chap. 5- Net2 21
Network Layer In
The Internet
The IP Protocol
Application protocols include:
SMTP:
The Simple Mail Transfer Protocol is used to send mail from one machine to another.
SNMP:
The Simple Network Management Protocol provides monitoring and managing capabilities
for a network.
Telnet:
Provides remote login service. It allows a user on one machine to log into another machine
on the network.
FTP:
The File Transfer Protocol copies arbitrary files (e.g. binary, data, and source) from one
machine to another.
SSH, RLOGIN, RSH:
Methods for logging on to a remote machine.
22. Chap. 5- Net2 22
Network Layer In
The Internet
The IP Protocol
Network Byte Order
One problem that often arises is that different machines represent integers in different ways:
Big Endian machines such as IBM and Sun-3 computers store the most significant byte of
a 32-bit integer in the lowest memory address of the word (e.g. to the left).
• The integer 0x01020304 is laid out in memory as bytes 0x01, 0x02, 0x03, and 0x04.
Little Endian machines such as the Intel Processor store the most significant byte at the
highest address.
• The integer 0x01020304 is laid out in memory as bytes 0x04, 0x03, 0x02, 0x01.
Other machines (such as DEC-10s) use 36-bit words to hold integers.
As with all network protocols, the standards specify the meanings of all bits in each field,
right down to the bit and byte order.
The Internet defines a network Big Endian standard byte order that is used when referring to
the fields of Internet datagrams.
23. Chap. 5- Net2 23
Network Layer In
The Internet
The IPV4 Protocol
INTERNET PROTOCOL (IP)
The goal of IP is to interconnect networks of diverse technologies and create a single,
virtual network to which all hosts connect.
Hosts communicate with other hosts by handing datagrams to the IP layer;
• The sender doesn't worry about the details of how the networks are actually
interconnected.
• IP provides unreliable, connectionless delivery service.
• IP defines a universal packet called an Internet Datagram.
All Internet hosts and gateways
process IP datagrams.
24. Chap. 5- Net2 24
Network Layer In
The Internet
The IPV4 Protocol
1. Version number (4-bits):
• The current protocol version is 4.
• Including a version number allows a future version of IP be used along side the current
version, facilitating migration to new protocols.
2. Header length (4-bits):
• Length of the datagram header (excluding data) in 32-bit words.
• The minimum length is 5 words = 20 bytes, but can be up to 15 words if options are
used.
• In practice, the length field is used to locate the start of the data portion of the datagram.
25. Chap. 5- Net2 25
Network Layer In
The Internet
The IPV4 Protocol
3. Type-of-service (8-bits):
A hint to the routing algorithms as to what type of service we desire.
Precedence (3-bits): A priority indication, where 0 is the lowest and means normal service, while 7 is
highest and is intended for network control messages (e.g., routing, congestion control).
Delay (1-bit): An Application can request low delay service (e.g., for interactive use).
Throughput (1-bit): Application requests high throughput.
Reliability (1-bit): Application requests high reliability.
Note: These last three TOS bits will generally be mutually exclusive. Does setting the low-delay bit
guarantee getting such service? No. The type-of-service field is meant as a request or hint to the
routing algorithms, but does not guarantee that your request can be honored (e.g., there may not
be a low-delay path available).
In practice, routers ignore the TOS field in IPV4.
26. Chap. 5- Net2 26
Network Layer In
The Internet
The IPV4 Protocol
4. Total length (16-bits):
Total length of the IP datagram (in bytes), including data and header. The size of the data
portion of the datagram is the total length minus the size of the header.
27. Chap. 5- Net2 27
Network Layer In
The Internet
The IPV4 Protocol
5 - 8. Identification (16-bits), Flags (3-bits), Fragment offset (13-bits):
These three fields are used for fragmentation and reassembly.
• Gateways along a path are free to fragment datagrams as needed; hosts are
required to reassemble fragments before passing complete datagrams to the higher
layer protocols.
• Each fragment contains a complete copy of the original datagram header plus some
portion of the data.
• A receiving host must match arriving fragments with the proper original datagram.
• These fragments may be out of order and interleaved with other fragments.
• All fragments of a datagram will have the same source and destination IP address.
• But, other datagrams between those two machines will share these fields as well, so
this is not enough.
28. Chap. 5- Net2 28
Network Layer In
The Internet
The IPV4 Protocol
5 - 8. Identification (16-bits), Flags (3-bits), Fragment offset (13-bits) (Continued):
The identification field uniquely identifies fragments of the same original datagram.
Whenever a host sends a datagram, it sets the identification field of the outgoing datagram
and increments its local identification counter.
The offset field shows order of the fragments.
When a gateway fragments a datagram, it sets the offset field of each fragment to reflect at
what data offset with respect to the original datagram the current fragment belongs.
Fragmentation occurs in 8-byte chunks, so the offset holds the “chunk number”.
Gateways can further fragment fragments!
A 400-byte fragment having an offset of 300 chunks could be split into two 200-byte
fragments having offsets of 300 and 325 chunks, respectively.
29. Chap. 5- Net2 29
Network Layer In
The Internet
The IPV4 Protocol
We need to know when we’ve received all of the fragments. To help with this, the flags field
may contain:
A Don't Fragment indication (set by host, honored by gateways). (A 1-bit flag.)
The More Fragments field indicates that another fragment follows this one. This
fragment is not the last fragment of the original datagram.
An unfragmented datagram has an offset of 0, and a More Fragment bit of 0.
The last fragment of a fragmented datagram contains More Fragment = Clear and the Offset
non-zero.
Note:
The total length field of the IP header refers to the current datagram, not the original.
Thus, the More Fragment bit is needed in order for the recipient host to determine when it
has all fragments of a datagram.
30. Chap. 5- Net2 30
Network Layer In
The Internet
The IPV4 Protocol
5 - 8. Identification (16-bits), Flags (3-bits), Fragment offset (13-bits) (Continued):
Example:
Original Frame: IHL = 5, Length = 656, Fragment Offset = 0, More = 0
Fragment 1: IHL = 5, Length = 252, Fragment Offset = 0, More = 1
Fragment 2: IHL = 5, Length = 252, Fragment Offset = 29, More = 1
Fragment 3: IHL = 5, Length = 192, Fragment Offset = 58, More = 0
31. Chap. 5- Net2 31
Network Layer In
The Internet
The IPV4 Protocol
9. Time-to-live (8-bits):
• A counter that is decremented by each gateway.
• Should this hopcount reach 0, discard the datagram.
• Originally, the time-to-live field was intended to reflect real time.
• In practice, it is now a hopcount.
• The time-to-live field squashes looping packets.
• It also guarantees that packets don't stay in the network for longer than 255 seconds, a
property needed by higher layer protocols that reuse sequence numbers.
10. Protocol (8-bits):
• What type of data the IP datagram carries (e.g., TCP, UDP, etc.).
• Needed by the receiving IP to know the higher level service that will next handle the
data.
32. Chap. 5- Net2 32
Network Layer In
The Internet
The IPV4 Protocol
11. Header Checksum (16-bits):
A checksum of the IP header (excluding data).
The IP checksum is computed as follows:
Treat the data as a stream of 16-bit words (appending a 0 byte if needed).
Compute the 1's complement sum of the 16-bit words. Take the 1's complement of
the computed sum.
This checksum is much weaker than the CRCs we have studied.
But, it has the property that the order in which the 16-bit words are summed is irrelevant.
We can place the checksum in a fixed location in the header, set it to zero, compute the
checksum, and store its value in the checksum field.
On receipt of a datagram, the computed checksum calculated over the received packet
should be zero.
Check summing only the header reduces the processing time at each gateway, but forces
transport layer protocols to perform error detection (if desired).
The header must be recalculated at every router since the time_to_live field is decremented.
33. Chap. 5- Net2 33
Network Layer In
The Internet
The IPV4 Protocol
12. Source address (32-bits):
Original sender's address. This is an IP address, not a MAC address.
13. Destination address (32-bits):
Datagram's ultimate destination.
Note: When a gateway forwards a frame to another gateway, it forwards an Ethernet frame.
The IP embedded datagram contains the source of the original sender (not the forwarding
gateway) and the destination address of the ultimate destination.
34. Chap. 5- Net2 34
Network Layer In
The Internet
The IPV4 Protocol
14. IP Options
IP datagrams allow the inclusion of optional, varying length fields that need not appear in every
datagram. We may sometimes want to send special information, but we don't want to dedicate a
field in the packet header for this purpose.
Options start with a 1-byte option code, followed by zero or more bytes of option data.
The option code byte contains three parts:
copy flag (1 bit): If 1, replicate option in each fragment of a fragmented datagram. That is, this option
should appear in every fragment as well. If 0, option need only appear in first fragment.
option class (2 bits): Purpose of option:
0 = network control
1 = reserved
2 = debugging and measurement
3 = reserved
option number (5 bits): A code indicating the option's type. See Figure 5.46 for these.
35. Chap. 5- Net2 35
Network Layer In
The Internet
IPV4 Addresses
In the Internet, names consist of human-readable strings such as osborne, babbage, or
jbreecher@clarku.edu or jb@sw.stratus.com.
Addresses consist of compact, 32-bit identifiers. Internet software translates names into addresses and
addresses into names; lower protocol layers always uses addresses rather than names.
Internet addresses are hierarchical, consisting of two parts:
• network: The network part of an address identifies which network a host is on. Conceptually, each
LAN has its own unique IP network number.
• local: The local part of an address identifies which host on that network.
We'll look at subnets that add a third level to the hierarchy. With subnetting, the local part may consist of
a `site'), which is further broken down into local network number, local host.
The Internet consists of a collection of physical networks, each of which is assigned a unique number.
The network number is used to route between gateways.
Only the gateway on the same network as the destination uses the local part of the address in
forwarding a datagram.
Analogy: Zip codes get a letter to the local post office, the address takes it from the post office to your
house.
36. Chap. 5- Net2 36
Network Layer In
The Internet
IPV4 Addresses
Class A addresses start with a `0' in the most
significant bit, followed by a 7-bit network
address and a 24-bit local part.
Class B addresses start with a `10' in the two most
significant bits, followed by a 14-bit network
number and a 16-bit local part.
Class C addresses start with a `110' in the three
most significant bits, followed by a 21-bit
network number and an 8-bit local part.
Class D addresses start with a `1110' in the four
most significant bits, followed by a 28-bit group
number. Used for multicast.
Class E addresses start with a ‘11110’ and are
reserved for future use.
Address Classes
The Internet designers were unsure whether the world would evolve into a few networks with many
hosts (e.g., large networks), or many networks each supporting only a few hosts (e.g., small
networks).
Thus, Internet addresses handle both large and small networks.
Internet address are four bytes in size, where:
37. Chap. 5- Net2 37
Network Layer In
The Internet
IPV4 Addresses
38. Chap. 5- Net2 38
Network Layer In
The Internet
IPV4 Addresses
Address Classes
The use of fixed-sized IP addresses makes the routing operation efficient.
In the ISO world, addresses are of varying format and length and extracting the address
from the packet may not be straightforward.
Registration of addresses is through the NIC (Network Information Center.)
See Figure 5.48 for the use of special addresses.
39. Chap. 5- Net2 39
Network Layer In
The Internet
IPV4 Addresses
Address Classes
Sample addresses can be obtained by using gethostbyname.
1998 Addresses 2002 Addresses
garden.wpi.edu 130.215.8.145 (class B) 130.215.28.200 (class B)
wpi.edu: 130.215 (a network addr) 130.215.24.6
gwen.cs.purdue.edu: 128.10.3.8 (class B)
eznet.net: 198.70.51.10 (Class C) 209.105.128.10
home.eznet.net 205.247.58.99 (Class C)
stanford.edu: 36.56.0.10 (class A)
breecher.net 216.168.224.70
clark.edu 192.102.5.4
babbage.clarku.edu 140.232.101.102
osborne.clarku.edu 140.232.101.115 (Class ?)
www.microsoft.com 207.46.197.102
207.46.197.113
207.46.230.218
207.46.230.219
207.46.230.220
207.46.197.100
40. Chap. 5- Net2 40
Network Layer In
The Internet
IPV4 Addresses
Address Classes
Note: Internet addresses refer to network connections rather than hosts.
a) Gateways, for instance, have two or more network connections and each interface
has its own IP address.
b) There is not a one-to-one mapping between host names and IP addresses.
Internet addresses are hierarchical addresses.
a) Datagrams are initially routed only by network number.
b) Only the gateway connected to the destination network uses the local part while
performing the routing operation.
What happens to a host's internet address if that host moves from one network to another?
a) Its Internet address must change.
b) It’s important to distinguish between a machine's name and its address.
c) Physical (ethernet) address is constant, network (IP) address may change.
41. Chap. 5- Net2 41
Network Layer In
The Internet
Subnets
Goals:
• We want to be able to reduce the number of networks seen by the outside world;
• We want to simplify the management of those many networks within the organization;
• We want to be able to slice the network/node “pie” in various ways.
1. A large organization or campus might have 30 or more LANs (one for each
department).
2. An organization will probably have only a single connection to the rest of the Internet.
3. In order for every local host to be able to communicate with other Internet machines,
routing entries for each of the 30 networks must exist in the core gateways.
4. In order for other sites to be able to respond to our queries, they must be able to
route packets back to us.
5. Wouldn't it be nice if we only needed to advertise a single network number for all 30
networks?
The Answer:
• Subnet addressing is a technique that allows a set of multiple, interconnected
networks to be covered by a single IP network number.
• IP addresses have a well-defined structure that allows a gateway to extract the
network portion of an address by simply looking at its class and an optional netmask.
This usage of “Subnets” is different from that we used
before to define the routers and lines in a network.
42. Chap. 5- Net2 42
Network Layer In
The Internet
Subnets
With subnetting, the local part of an IP address is further subdivided into a network and a
host part:
Consider two addresses 128.204.2.29 and 128.204.3.109.
Are they on the same network?
NO.
• They refer to hosts on the same network address (128.204), but they can actually be on
different ethernets connected by a bridge.
• To do this, we divide the local part (the two bytes to the right of 128.204) into a 1-byte
network part and a 1-byte host part.
• When sending data to 128.204.3.109 local gateways first route datagrams to the
(sub)network 128.204.3 rather than (IP network) 128.204.
• 128.204.2 and 128.204.3 are distinct (sub)networks.
• To the outside world, there is only a single network 128.204.
• Each of the individual networks is called a subnet.
43. Chap. 5- Net2 43
Network Layer In
The Internet
Subnets
With subnetting, the local part of an IP address is further subdivided into a network and a host
part:
Consider two addresses 128.204.2.29 and 128.204.3.109.
Are they on the same network?
YES.
• They refer to hosts on the same network address (128.204), but they can actually be on
the same ethernet.
• To do this, we divide the local part (the two bytes to the right of 128.204) into a 7-bit
network part and a 9-bit host part.
• Our example above is a Class B address; the technique applies also to Classes A and C.
44. Chap. 5- Net2 44
Network Layer In
The Internet
Subnets
To implement subnetting, hosts and gateways use a subnet mask to extract the network
part of an IP address. This mask can be seen in Figure 5.49. In this example, 6 bits
are reserved for subnet, and 10 bits for host.
To distinguish between direct (the router knows how to get to the destination) and indirect
(the router sends the packet off for someone else to figure it out) routing,
Without subnets, a router has tables of the form:
(other_network, 0) and (this_network, host).
With subnets, a router has tables of the form:
(this_network, subnet, 0) and (this_network, this_subnet, host).
45. Chap. 5- Net2 45
Network Layer In
The Internet
Subnets
1. Determining the subnetwork number of a network interface:
a) Each network interface has a subnet mask.
b) The subnet mask ANDed with the interface address yields the network number of
the interface.
2. For each of the machine's interface ports (hosts usually have only one, routers have
many):
a) Extract the destination address DEST from the datagram.
b) If ( ( port_interface_address & subnet_mask ) == ( DEST & subnet_mask ) ),
direct routing with this port can be used.
The routing algorithms described earlier remain essentially the same when subnetting is in
use.
a) Routing algorithms may need to propagate the mask with a network number in
routing updates.
b) They need the mask to extract (sub)network numbers.
c) Subnetting extends the number of levels in the Internet's hierarchical routing scheme.
d) It trades off optimality of routes vs. table space in gateways.
Host can find out its mask: Host sends ICMP address mask requests; responses contain
the mask for the local network.
48. Chap. 5- Net2 48
Network Layer In
The Internet
Internet Control Protocols
INTERNET CONTROL MESSAGE PROTOCOL (ICMP)
The Internet Control Message Protocol (ICMP) allows gateways and hosts
to send network control information to each other.
From a layering point of view, ICMP is a separate protocol that sits above
IP and uses IP to transport messages.
In practice, ICMP is an integral part of IP and all IP modules must support
the ICMP protocol.
ICMP datagrams are encapsulated within IP datagrams and processed by
IP in the same way as TCP and UDP datagrams;
if special processing is needed, the IP type-of-service (TOS) field could be
used.
IP
Transport
TCP/UDP
ICMP
49. Chap. 5- Net2 49
Network Layer In
The Internet
Internet Control Protocols
INTERNET CONTROL MESSAGE PROTOCOL (ICMP)
There are two general types of ICMP messages:
Information messages, where a sender sends a query to another
machine (either host or gateway) and expects an answer. For
example, a host might want to know if a gateway is alive.
Error indication messages, where the IP software on a host or
gateway has encountered a problem processing an IP datagram.
For example, it may be unable to route a datagram to its
destination, or it may have had to drop a frame.
There are a number of message types of which we will talk about
only a few:
IP
Transport
TCP/UDP
ICMP
50. Chap. 5- Net2 50
Network Layer In
The Internet
Internet Control Protocols
Echo Requests
The ICMP echo request and echo reply messages are useful for network debugging.
If machine A sends an echo request message to machine B, machine B is required to
respond with an ICMP echo reply.
Most systems supply an application program that sends and receives ICMP echo
messages.
In UNIX, the program ping allows a user to check whether a machine is reachable and
functioning.
Because ICMP messages are handled just like other IP datagrams, ICMP echo messages
test the reach-ability of any host. Also, because ICMP is an integral part of IP, all hosts
and gateways must implement ICMP.
51. Chap. 5- Net2 51
Network Layer In
The Internet
Internet Control Protocols
Timestamp Messages
ICMP timestamp messages are used to estimate the transmission delays between
machines and to synchronize clocks:
Including both the receive and transmit timestamp allows the sending host to determine the
fraction of time spent transmitting vs. processing the request.
By averaging the measurements of several messages, the sender can estimate the offset
between its local clock and that on the remote machine. Note: it is quite feasible to
synchronize the clocks of all machines on a LAN to within several milliseconds of each
other.
52. Chap. 5- Net2 52
Network Layer In
The Internet
Internet Control Protocols
When an IP module encounters an error while processing a datagram, it sends an ICMP
error message back to the original sender of the datagram. Errors include:
Destination Unreachable: When a gateway cannot route a datagram (e.g., it doesn't
have an appropriate route in its local table), it discards the message and returns an
ICMP "destination unreachable" message to the sending host. In effect, the host
needs different routing or needs to try again later.
Time Exceeded: As a datagram is processed, gateways decrement its time-to-live
(TTL) field. If the TTL value reaches 0, the gateway discards the datagram and
sends a time exceeded message to the sender. The data portion of the message
includes part of the offending datagram's header.
Parameter Problem: When a host or gateway encounters a problem parsing an IP
datagram, it returns a parameter problem message to the datagram's sender:
Source Quench: When a gateway becomes congested and runs out of buffer space,
it may discard a datagram and return a source quench message. Source quench
messages are used to request that the sender reduce the rate at which it is sending
datagrams.
53. Chap. 5- Net2 53
Network Layer In
The Internet
Internet Control Protocols
MAPPING BETWEEN INTERNET AND PHYSICAL ADDRESSES
Suppose we have two machines A and B connected to the same network, and A wants to
send an internet datagram to B.
A must know B 's data link layer (MAC) address in order to send frames to B.
The problem of mapping Internet addresses to physical addresses is known as the address
resolution problem.
1. Each e-net device has its own unique number. Change the card and you change its
physical address.
2. Physical address are 6 bytes long, too large to multiplex within an Internet address.
3. New machines can be added to the network with no disruption of service.
4. But, adding new hosts should not require reconfiguring existing hosts to inform them
of the new machine.
54. Chap. 5- Net2 54
Network Layer In
The Internet
ARP
ARP
The Address Resolution Protocol (ARP) is a protocol that allows hosts to dynamically map
Internet addresses to physical addresses:
1. The requesting machine only needs to know the target machine's IP address.
2. It sends out a special ARP request frame using the Ethernet's broadcast capability.
Thus, every machine on the LAN will receive the ARP request.
3. The ARP request asks `what is the Ethernet address of Internet address A.B.C.D'?
4. Each machine receives a copy of the broadcast message, and the machine having
the desired IP address responds with its Ethernet address.
Of course, a machine doesn't send out an ARP packet each time it wishes to send an IP
datagram.
Instead, each machine maintains a cache of recently used mappings, and an ARP request
is only sent if the desired mapping is not already in the cache.
55. Chap. 5- Net2 55
Network Layer In
The Internet
ARP
ARP request packets also contain the sender's IP and Ethernet address
pair.
• This eliminates the need for a second ARP request.
If machine A wishes to communicate with machine B, there is high
probability that B will need A 's Ethernet address as well.
Since every machine receives every ARP request (which is broadcast),
how about adding the source address in each ARP request to the
cache?
• Not a terribly good idea.
• Although a network may consist of hundreds of machines, a given
host is unlikely to actively communicate with more than a few at any
one time.
• Thus, adding every mapping to the local cache is likely to waste
memory, and may cause the flushing of entries that will be used
again soon to make room for entries that will never be used.
IP
Transport
TCP/UDP
ARP
DLL
56. Chap. 5- Net2 56
Network Layer In
The Internet
ARP
Solution:
Upon receipt of an ARP request from a machine whose IP address is already in the local
ARP cache, update the information for that entry.
• This handles the case of a machine whose Ethernet address changes; ARP entries with
the old value will be overwritten with the new value.
For a target on a remote network, it's a bit more complicated. Broadcasts don't cross
routers. So, the requester, seeing that a request is remote, essentially needs to hand it
off to a router to handle further.
From a layering point of view, ARP sits below IP, but above the data link layer.
IP
Transport
TCP/UDP
ARP
DLL
57. Chap. 5- Net2 57
Network Layer In
The Internet
ARP
ARP Details
Conceptually, ARP consists of two parts: the software responsible for finding the physical
address of an IP address (e.g., a client), and the software responsible for answering
ARP requests from other machines (e.g., a server).
When sending an IP datagram, the sender searches its local ARP cache for the desired
target address. If found, ARP is done.
If not found, send out a broadcast ARP request and wait for the response.
In practice, waiting for a response is somewhat tricky, because the target machine may be
down, the request might become lost and need to be retransmitted, and so forth.
58. Chap. 5- Net2 58
Network Layer In
The Internet
ARP
ARP packets have been designed in a general way so that the protocol can be used over many different
network technologies. ARP packets have the following format:
1. The 2-byte Hardware-Type field gives the type of the hardware address we are interested in
(e.g., 1 for Ethernet).
2. The 2-byte Protocol-Type field gives the type of the higher level protocol address we are
interested in (e.g., 0x0800 for IP). Note, it is two bytes long, just like the Ethernet type field.
3. A 1-byte Hardware-Length field specifying the length of the hardware address (6 bytes would be
the length for Ethernet).
4. A 1-byte Protocol-Length field specifying the length of the target protocol address (4 for IP).
5. A 16-bit Operation Code field specifying the operation desired (e.g., REQUEST or RESPONSE).
6. The sender's Ethernet address (Sender Hardware Address) (if known).
7. The sender's Internet address (Sender Protocol Address) (if known).
8. The target's Ethernet address (Target Hardware Address) (filled in response).
9. The target's Internet address (Target Protocol Address) (filled in response).
59. Chap. 5- Net2 59
Network Layer In
The Internet
Reverse ARP
ARP handles the problem of determining the hardware address that corresponds to a given IP address.
But how do I find my own IP address? The protocol that maps hardware addresses to Internet
addresses is called Reverse ARP, or RARP.
Necessary when a diskless machine first boots. It doesn't know its own IP address (and can't read it
from a local disk!). The booting client contacts a server to obtain its Internet address.
1. The client communicates with a server by using a special protocol that requires only Ethernet
frames. In essence it says "My ethernet address is aa.bb.cc.dd.ee.ff. Does anyone know my IP
address?"
2. The broadcast goes to all nodes, including the RARP server. The RARP server maintains a
database of physical address to Internet address mappings.
The actual format of RARP messages is similar to those of ARP:
The Ethernet frame type is set to type RARP (0x8035), and RARP defines two new message
types; `RARP request' and `RARP response'.
The remaining fields are the same as in ARP.
We now see one of the primary benefits of broadcasting; locating servers.
However, because broadcasting is resource intensive, (every machine on the local network must
process the message, even if only to reject it) broadcasting should be used sparingly.
60. Chap. 5- Net2 60
Network Layer In
The Internet
DHCP
DHCP: Dynamic Host Configuration Protocol (RFC 1531)
Used to match workstations with an IP address. This address can be changed every
time the machine boots. Allows configuration flexibility.
Here’s the protocol:
1. Workstation broadcasts DHCPDISCOVER message on power-up.
2. Several DHCP Servers may respond with DHCPOFFER messages containing:
IP address, subnet mask
Router address
Renewal Time
1. Workstation responds to one offer with DHCPREQUEST.
Request may include items like: DNS servers, time servers, boot files,
DHCP Server now binds IP address and replies with DHCPACK message with
requested options.
Manager assigns multiple ranges of IP addresses to each DHCP server and server
manages distribution to clients.
Client must renew IP address at regular intervals indicated by Renewal Time.
61. Chap. 5- Net2 61
Network Layer In
The Internet
Gateway Protocol
AS - Autonomous System:
Those networks run by independent organizations (for instance, companies.)
Administrative regions that contain a set of networks and gateways.
A site is free to manage routing within its region any way it wishes, and routing information flows among
regions only through carefully controlled mechanisms.
IGP - Interior Gateway Protocol:
A routing protocol that's run within an AS.
1. ASs must be able to isolate themselves from other sites. They should be able to keep their local
internets operating even when other parts of the Internet have failed.
2. Local gateways (probably) don't want to know (in much detail) about topological changes that take
place far away.
3. Sites want administrative control over their gateways and networks and may not want to run the
same routing protocols as other sites.
EGP - Exterior Gateway Protocol:
A routing protocol that's run between ASs. The `glue' that ties autonomous systems together. It:
1. Allows a site to advertise to the rest of the world a path to the networks within its autonomous
system.
2. Allows sites to learn about networks located in other autonomous regions.
62. Chap. 5- Net2 62
Network Layer In
The Internet
Interior Gateway Protocol - OSPF
OSPF – Open Shortest Path First
Becoming the primary IGP. Allows an addressing hierarchy and thus makes routing easier.
The requirements used when designing OSPF included:
1. Had to be "Open" - published in the literature.
2. Had to support a number of "distance" metrics, including physical length, delay, capacity, etc.
3. Had to be dynamic, able to adapt to changing topologies.
4. Had to support "type of service" - able to change routing behavior based on frame characteristics.
5. Had to do load balancing; able to use multiple routes rather than one at a time.
6. Had to support hierarchical systems so that no one router needed to understand the entire flat
network.
7. Had to provide some kind of security.
63. Chap. 5- Net2 63
Network Layer In
The Internet
Interior Gateway Protocol - OSPF
OSPF supports three kinds of networks:
1. Point to point lines between two routers.
2. Multiaccess networks with broadcasting (LANs).
3. Multiaccess networks without broadcasting
(packet switched WANs ).
[Here a multiaccess network is one that has multiple
routers, each of which can talk to all the other
routers. This is a common LAN/WAN property.]
As OSPF is defined, it:
1. Divides an Autonomous System into “areas”.
An area is a network or set of contiguous
networks. All routers in an AS do not need to
be in an Area.
2. Uses a link-state algorithm within an area.
Thus distances are calculated based on length,
or other properties. See Figure 5.52
64. Chap. 5- Net2 64
Network Layer In
The Internet
Interior Gateway Protocol - OSPF
As OSPF is defined (continued), it:
3. Utilizes a Backbone. All areas are
connected to the backbone so packets
can travel from area to area via the
backbone.
4. Employs four classes of routers see
Figure 5.53
Internal routers connecting
networks wholly within one area.
Backbone routers on the backbone
area.
Area border routers connecting two
or more areas (includes connecting
the backbone with an area.)
AS boundary routers which talk to
routers in other ASes.
65. Chap. 5- Net2 65
Network Layer In
The Internet
Interior Gateway Protocol - OSPF
As OSPF is defined (continued), it:
5. Supports type of service routing. It provides for multiple paths, with gateways choosing
paths based on the type of service field in IP headers.
6. Supports multipath routing. It distributes traffic over multiple paths to a destination.
7. Includes integrated support for subnetting. Specifically, (network number, network mask)
pairs are distributed in updates.
8. Authenticates updates: Unauthenticated updates make the network extremely vulnerable
to denial of service attacks (e.g., any workstation can send out bogus updates that break
routing).
66. Chap. 5- Net2 66
Network Layer In
The Internet
Exterior Gateway Protocol - BGP
BORDER GATEWAY PROTOCOL (BGP)
BGP is the current Exterior Gateway Routing Protocol ( EGP ) used.
Distance vector protocol, but not only does it account for distance, but also for specific route
criteria.
BGP can take into account politics, security and economic issues.
67. Chap. 5- Net2 67
Network Layer In
The Internet
IPv6
Motivation:
1. We will run out of Class B addresses soon (within years).
2. The entire address space of 32 bits will eventually be exhausted. Although 32 bits is 4 billion
nodes, hierarchical routing doesn't distribute addresses evenly.
3. We simply don't know how to scale routing beyond a few tens of thousands of networks. Thus,
increasing the size of IP addresses solves problems 1 and 2, but doesn't help with the scaling
problem.
This is an engineering problem in the sense that distributing routing updates, computing new routing
tables, and holding all routes in memory uses processor and memory resources.
We can do that for 10,000 networks, maybe even 100,000, but not 1,000,000. Finding the right balance
between these costs is difficult.
Need for more addresses provides an opportunity to improve upon other aspects of current IP (IPv4).
Look at header in Figure 5.56 , and address space use in Figure 5.57 on the next page.
During transition period, IPv4 addresses will be included in IPv6 addresses.
71. Chap. 5- Net2 71
Examples
TCP/IP Routing
F r o m 1 4 0 . 1 9 2 . 3 4 . 3 4 t o 1 4 0 . 1 9 2 . 1 0 . 5
1 4 0 . 1 9 2 . 3 4 . 3 4 k n o w s t h a t 1 4 0 . 1 9 2 . 1 0 . 5 i s n ' t o n t h e s a m e n e t a n d s e n d s i t t o r o u t e r a t 1 4 0 . 1 9 2 . 3 4 . 1
N o t e D A f o r l a y e r 2
I n s i d e t h e r o u t e r t h e L a y e r 2 h e a d e r s a n d t r a i l e r s a r e r e m o v e d l e a v i n g o n l y t h e
l a y e r 3 p a c k e t .
T h e r o u t e r l o o k s u p t h e p a c k e t ' s D A i n t h e r o u t i n g t a b l e a n d f o r w a r d s t o t h e
a p p r o p r i a t e i n t e r f a c e .
A t t h e i n t e r f a c e , l a y e r 2 h e a d e r s a n d t r a i l e r s a r e a d d e d b a c k .
D A i s t h e a d d r e s s o f t h e d e s t i n a t i o n h o s t .
S A i s t h e a d d r e s s o f t h e r o u t e r .
F C S i s r e c a l c u l a t e d .
0 0 C 0 C 1 A A 3 4 1 3 I P 1 4 0 . 1 9 2 . 1 0 . 50 0 6 0 C A 1 1 4 4 9 9 D a t a F C S1 4 0 . 1 9 2 . 3 4 . 3 4
1 4 0 . 1 9 2 . 1 0 . 5 D a t a1 4 0 . 1 9 2 . 3 4 . 3 4
0 0 6 0 C A 2 3 B E 4 5 I P 1 4 0 . 1 9 2 . 1 0 . 50 0 C 0 C 1 A A 3 4 1 1 D a t a F C S1 4 0 . 1 9 2 . 3 4 . 3 4
140.192.10.5
0060CA23BE45
140.192.10.25
0060CA34CD29
140.192.100.34
0060CA4AD2EE
140.192.100.8
0060CAAABBCC
140.192.201.22
0060CA3499CC
140.192.201.126
0060CA3499DE
140.192.34.34
0060CA114499
140.192.34.35
0060CA7819AA
Router
140.192.201.1
00C0C1AA3410
140.192.10.1
00C0C1AA3411
140.192.100.1
00C0C1AA3412
140.192.34.1
00C0C1AA3413
73. Chap. 5- Net2 73
Network Layer In
The Internet
Some Useful Tools
Find out where a web site is located.
www.netsol.com/cgi-bin/whois/whois
Netstat - tells you about the connections you have open on your machine.
Ping - tells you how long it takes to get to a destination (and if there is a
route to that destination.
Arp - gives information about the routing table.
Finger - tells you who is logged on.
ftp - gets you data from a remote site.
Route - tells you information about the routing tables.
Netsh – lots of niffty data.
Telnet – allows you to log on to a remote host.
Tracert – Find the paths to remote sites. A useful site is www.traceroute.org
These tools are available on your
windows machine in c:winntsystem32
74. Chap. 5- Net2 74
128.32.4.0
R3
R1
R2
A B C
D E
F
G
Z
R4
128.32.3.0
128.32.2.0
128.32.1.0
.15
.16
.4
.8
.11
.13
.10
.1
.5
.7
.3
.6
.12
.14
.17
.2
Figure 1. Network Topology
Network Layer In
The Internet
An Example Network
.
75. Chap. 5- Net2 75
Network Layer In
The Internet
An Example Network
.
Table 1: Ethernet addresses, by IP address.
IP Address Ethernet Address Alias IP Address Ethernet Address Alias
128.32.1.1 08:00:20:21:77:b2 EA-1 128.32.2.14 08:00:09:24:a4:11 EA-9
128.32.1.2 00:a0:c9:2a:1f:69 EA-2 128.32.2.17 08:00:20:7e:82:91 EA-10
128.32.1.10 00:a0:c9:2a:1f:53 EA-3 128.32.3.7 08:00:20:1a:df:ff EA-11
128.32.1.11 00:a0:c9:2a:1e:d8 EA-4 128.32.3.8 08:00:20:1b:52:7d EA-12
128.32.1.12 00:60:8c:36:b2:7f EA-5 128.32.3.15 08:00:20:0b:2a:8b EA-13
128.32.2.3 00:60:8c:52:d0:00 EA-6 128.32.3.16 08:00:20:7e:d3:27 EA-14
128.32.2.6 08:00:20:81:b9:d0 EA-7 128.32.4.4 08:00:07:46:29:4c EA-15
128.32.2.13 08:00:20:23:79:ee EA-8 128.32.4.5 08:00:07:17:9b:7d EA-16
Table 2: Routing Tables for Selected Nodes
Router or Host Destination Next Hop
A: 128.32.1.10 128.32.1.0
default
direct, Ethernet, port 1
(R1) 128.32.1.1
R1: 128.32.1.1
or 128.32.4.5
128.32.1.0
128.32.4.0
128.32.2.0
128.32.3.0
direct, Ethernet, port 1
direct, Ethernet, port 2
(R4) 128.32.4.4
(R4) 128.32.4.4
R2: 128.32.1.2
or 128.32.2.6
128.32.1.0
128.32.2.0
128.32.3.0
128.32.4.0
direct, Ethernet, port 1
direct, Ethernet, port 2
(R3) 128.32.2.3
(R1) 128.32.1.1
R3: 128.32.2.3
or 128.32.3.7
128.32.2.0
128.32.3.0
128.32.1.0
128.32.4.0
direct, Ethernet, port 1
direct, Ethernet, port 2
(R3) 128.32.2.6
(R4) 128.32.3.8
R4: 128.32.4.4
or 128.32.3.8
128.32.4.0
128.32.3.0
128.32.1.0
128.32.2.0
direct, Ethernet, port 1
direct, Ethernet, port 2
(R1) 128.32.4.5
(R3) 128.32.3.7
Z: 128.32.2.17 128.32.2.0
default
direct, Ethernet, port 1
(R2)128.32.2.6