1. The document discusses the link layer in computer networks, including MAC addresses, ARP, Ethernet frames, and switches. MAC addresses are used locally to deliver frames between connected interfaces, while IP addresses are used for network layer forwarding.
2. ARP is used to map IP addresses to MAC addresses on the same local area network (LAN). Each node maintains an ARP cache that maps IP addresses to MAC addresses of other nodes on the LAN.
3. Switches learn the location of nodes by examining the source MAC addresses of received frames. They build forwarding tables that map MAC addresses to switch ports. This allows frames to be selectively forwarded to the correct destination port, improving scalability over hubs.
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.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.
DSDV is a proactive routing protocol that uses destination sequence numbers to ensure loop-free routing in mobile ad hoc networks. Each node maintains a routing table with destination addresses, next hops, metrics, and sequence numbers. Nodes periodically broadcast their full routing tables, and also broadcast updates immediately after changes to avoid counting to infinity problems. DSDV aims to limit unnecessary route advertisements through a mechanism to dampen fluctuations in routing tables.
Proactive routing protocol
Each node maintain a routing table.
Sequence number is used to update the topology information
Update can be done based on event driven or periodic
Observations
May be energy expensive due to high mobility of the nodes
Delay can be minimized, as path to destination is already known to all nodes.
This document discusses the Internet Protocol (IP) version 4 and 6. It describes the key tasks of IP including addressing computers and fragmenting packets. IP version 4 uses 32-bit addresses while IP version 6 uses 128-bit addresses and has improvements like larger address space and better security. The document also covers IP address classes, private addressing, subnetting, Classless Inter-Domain Routing (CIDR), and address blocks.
Distance vector routing works by having each node maintain a routing table with the minimum distance to reach every other node. Nodes share their routing tables with immediate neighbors periodically or when changes occur, allowing each node to learn optimal routes throughout the network. Each node sends only the minimum distance and next hop information to neighbors, who update their own tables. This sharing of routing information allows all nodes to gradually learn the least-cost routes.
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.
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.
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.
The data link layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment.
DSDV is a proactive routing protocol that uses destination sequence numbers to ensure loop-free routing in mobile ad hoc networks. Each node maintains a routing table with destination addresses, next hops, metrics, and sequence numbers. Nodes periodically broadcast their full routing tables, and also broadcast updates immediately after changes to avoid counting to infinity problems. DSDV aims to limit unnecessary route advertisements through a mechanism to dampen fluctuations in routing tables.
Proactive routing protocol
Each node maintain a routing table.
Sequence number is used to update the topology information
Update can be done based on event driven or periodic
Observations
May be energy expensive due to high mobility of the nodes
Delay can be minimized, as path to destination is already known to all nodes.
This document discusses the Internet Protocol (IP) version 4 and 6. It describes the key tasks of IP including addressing computers and fragmenting packets. IP version 4 uses 32-bit addresses while IP version 6 uses 128-bit addresses and has improvements like larger address space and better security. The document also covers IP address classes, private addressing, subnetting, Classless Inter-Domain Routing (CIDR), and address blocks.
Distance vector routing works by having each node maintain a routing table with the minimum distance to reach every other node. Nodes share their routing tables with immediate neighbors periodically or when changes occur, allowing each node to learn optimal routes throughout the network. Each node sends only the minimum distance and next hop information to neighbors, who update their own tables. This sharing of routing information allows all nodes to gradually learn the least-cost routes.
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.
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.
Congestion avoidance mechanisms aim to predict impending congestion and reduce data transmission rates before packet loss occurs. Three main methods are DEC bit, Random Early Detection (RED), and source-based approaches. DEC bit uses routers to explicitly notify sources of congestion. RED drops packets probabilistically based on average queue length to implicitly notify sources. Source-based methods monitor round-trip times and window sizes to detect congestion and adjust transmission rates accordingly.
This document discusses and compares two routing protocols: distance vector routing and link state routing. Distance vector routing involves each node sharing its routing table only with its neighbors, while link state routing involves each node having knowledge of the entire network topology. The document outlines the working principles, drawbacks like count to infinity, and pros and cons of each approach.
Computer Networks Unit 1 Introduction and Physical Layer Dr. SELVAGANESAN S
This document discusses data communication and computer networks. It defines data communication as the exchange of data between devices via transmission medium. A data communication system has five components: sender, receiver, message, medium, and protocol. Communication can be simplex, half-duplex, or full-duplex. The document also defines networks, explaining that a network allows interconnected devices to communicate and share resources. Local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs) are described as the main categories of networks.
Unicast involves sending data from one computer to another, with one sender and one receiver. Multicast sends data to a group of devices that have joined the multicast group, with one sender but multiple potential receivers. Broadcast sends data from one computer that is then forwarded to all connected devices, with one sender and all devices receiving the broadcast traffic.
Subnets divide a network into smaller sub-networks or subnets. Each subnet is treated as a separate network and can be further divided. When a packet enters a network with subnets, routers will route based on the subnet ID which is a combination of the network ID and subnet portion of the IP address. Subnets are only relevant for routing within an organization and are transparent outside the organization.
This document discusses wireless sensor network applications and energy consumption. It provides examples of WSN applications including disaster relief, environment monitoring, healthcare, and more. It then discusses various factors that influence energy consumption in sensor nodes, including operation states, microcontroller usage, radio transceivers, memory, and the relationship between computation and communication. Specific power consumption numbers are given for different components like radios, sensors, and microprocessors. The goals of optimization for WSNs are discussed as quality of service, energy efficiency, scalability, and robustness.
How to put these nodes together to form a meaningful network.
How a network should function at high-level application scenarios .
On the basis of these scenarios and optimization goals, the design of networking protocols in wireless sensor networks are derived
A proper service interface is required and integration of WSNs into larger network contexts.
The document discusses the TCP/IP protocol suite and compares it to the OSI model. It describes the layers of the TCP/IP model including the physical, data link, internet, and transport layers. The transport layer uses TCP and UDP, with TCP being connection-oriented and reliable, while UDP is connectionless. The internet layer uses IP to transport datagrams independently. The OSI model has 7 layers while TCP/IP has 5 layers that do not directly correspond to the OSI layers.
HDLC is a bit-oriented protocol defined by ISO for point-to-point and multipoint communication over data links. It supports full-duplex communication and provides reliability, efficiency and flexibility. HDLC defines three types of stations - primary, secondary and combined. It uses three frame types - unnumbered, information and supervisory frames. HDLC also specifies three data transfer modes - normal response mode, asynchronous response mode and asynchronous balanced mode. [/SUMMARY]
The document discusses subnetting and provides an example of how to subnet the IP network address 192.168.1.128 into 6 subnets. It explains that subnetting allows a single network number to be shared among multiple physical networks. Each host is configured with an IP address and subnet mask, where the subnet is calculated by performing a bitwise AND of the IP address and subnet mask. The example shows how to determine the subnet mask is 255.255.255.224 when creating 6 subnets, and that each subnet can support up to 30 hosts.
ARP is a protocol that maps IP addresses to MAC addresses. It works by broadcasting an ARP request packet to all devices on the local network segment. The device with the matching IP address responds with its MAC address, allowing the requesting device to send packets directly to the destination MAC address on the local network.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
Fast Ethernet increased the bandwidth of standard Ethernet from 10 Mbps to 100 Mbps. It used the same CSMA/CD access method and frame format as standard Ethernet but with some changes to address the higher speed. Fast Ethernet was implemented over twisted pair cables using 100BASE-TX or over fiber optic cables using 100BASE-FX. The increased speed enabled Fast Ethernet to compete with other high-speed LAN technologies of the time like FDDI.
This document describes the sliding window protocol. It discusses key concepts like both the sender and receiver maintaining buffers to hold packets, acknowledgements being sent for every received packet, and the sender being able to send a window of packets before receiving an acknowledgement. It then explains the sender side process of numbering packets and maintaining a sending window. The receiver side maintains a window size of 1 and acknowledges by sending the next expected sequence number. A one bit sliding window protocol acts like stop and wait. Merits include multiple packets being sent without waiting for acknowledgements while demerits include potential bandwidth waste in some situations.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
This document discusses error detection and correction in data transmission. It describes single-bit errors, where one bit is corrupted, and burst errors, where multiple contiguous bits are corrupted. Error detection allows a receiver to detect if errors occurred, while error correction identifies the exact corrupted bits. Redundant bits are added to messages to enable detection and correction. Methods include forward error correction, retransmission, block coding, and convolution coding. Block coding divides messages into blocks with redundant bits added, creating codewords that allow error detection if a codeword is invalid.
Link-state routing protocols use Dijkstra's algorithm to calculate the shortest path to all destinations based on a link-state database containing the full network topology. Each router runs the same algorithm locally to determine the optimal path. Key aspects include link-state advertisements to share connectivity information, the topological database to store network maps, and shortest path first calculations to derive routes. Common link-state protocols are OSPF and IS-IS. They provide fast convergence and scalability but require more resources than distance-vector protocols.
The document discusses the Internet Control Message Protocol (ICMP). ICMP provides error reporting, congestion reporting, and first-hop router redirection. It uses IP to carry its data end-to-end and is considered an integral part of IP. ICMP messages are encapsulated in IP datagrams and are used to report errors in IP datagrams, though some errors may still result in datagrams being dropped without a report. ICMP defines various message types including error messages like destination unreachable and informational messages like echo request and reply.
Go-Back-N (GBN) is an ARQ protocol that allows a sender to transmit multiple frames before receiving an acknowledgement. The sender maintains a window of size N, meaning it can transmit N frames before waiting for a response. The receiver window is always size 1, acknowledging frames individually. If a frame times out without an ACK, the sender retransmits that frame and all subsequent frames in the window. GBN improves efficiency over stop-and-wait by allowing transmission of multiple frames while reducing waiting time at the sender.
Relational algebra is a procedural query language used to manipulate relations in a relational database. It consists of operators like select, project, join, union, and set difference. SQL is based on the concepts of relational algebra. Relational algebra expressions specify a sequence of operators to apply to relations in order to retrieve the desired data from the database. Some key operators include selection to filter tuples, projection to select attributes, and join to combine tuples from two relations based on a join condition.
This document summarizes key concepts from Chapter 14 of the textbook "Database System Concepts, 6th Ed." including:
1) A transaction is a unit of program execution that accesses and updates data items. For integrity, transactions must have ACID properties: atomicity, consistency, isolation, and durability.
2) Concurrency control ensures serializable execution of concurrent transactions to maintain consistency. Schedules must be conflict serializable and recoverable.
3) SQL supports transactions and different isolation levels to balance consistency and concurrency. The default isolation level is usually serializable but some systems allow weaker isolation.
Congestion avoidance mechanisms aim to predict impending congestion and reduce data transmission rates before packet loss occurs. Three main methods are DEC bit, Random Early Detection (RED), and source-based approaches. DEC bit uses routers to explicitly notify sources of congestion. RED drops packets probabilistically based on average queue length to implicitly notify sources. Source-based methods monitor round-trip times and window sizes to detect congestion and adjust transmission rates accordingly.
This document discusses and compares two routing protocols: distance vector routing and link state routing. Distance vector routing involves each node sharing its routing table only with its neighbors, while link state routing involves each node having knowledge of the entire network topology. The document outlines the working principles, drawbacks like count to infinity, and pros and cons of each approach.
Computer Networks Unit 1 Introduction and Physical Layer Dr. SELVAGANESAN S
This document discusses data communication and computer networks. It defines data communication as the exchange of data between devices via transmission medium. A data communication system has five components: sender, receiver, message, medium, and protocol. Communication can be simplex, half-duplex, or full-duplex. The document also defines networks, explaining that a network allows interconnected devices to communicate and share resources. Local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs) are described as the main categories of networks.
Unicast involves sending data from one computer to another, with one sender and one receiver. Multicast sends data to a group of devices that have joined the multicast group, with one sender but multiple potential receivers. Broadcast sends data from one computer that is then forwarded to all connected devices, with one sender and all devices receiving the broadcast traffic.
Subnets divide a network into smaller sub-networks or subnets. Each subnet is treated as a separate network and can be further divided. When a packet enters a network with subnets, routers will route based on the subnet ID which is a combination of the network ID and subnet portion of the IP address. Subnets are only relevant for routing within an organization and are transparent outside the organization.
This document discusses wireless sensor network applications and energy consumption. It provides examples of WSN applications including disaster relief, environment monitoring, healthcare, and more. It then discusses various factors that influence energy consumption in sensor nodes, including operation states, microcontroller usage, radio transceivers, memory, and the relationship between computation and communication. Specific power consumption numbers are given for different components like radios, sensors, and microprocessors. The goals of optimization for WSNs are discussed as quality of service, energy efficiency, scalability, and robustness.
How to put these nodes together to form a meaningful network.
How a network should function at high-level application scenarios .
On the basis of these scenarios and optimization goals, the design of networking protocols in wireless sensor networks are derived
A proper service interface is required and integration of WSNs into larger network contexts.
The document discusses the TCP/IP protocol suite and compares it to the OSI model. It describes the layers of the TCP/IP model including the physical, data link, internet, and transport layers. The transport layer uses TCP and UDP, with TCP being connection-oriented and reliable, while UDP is connectionless. The internet layer uses IP to transport datagrams independently. The OSI model has 7 layers while TCP/IP has 5 layers that do not directly correspond to the OSI layers.
HDLC is a bit-oriented protocol defined by ISO for point-to-point and multipoint communication over data links. It supports full-duplex communication and provides reliability, efficiency and flexibility. HDLC defines three types of stations - primary, secondary and combined. It uses three frame types - unnumbered, information and supervisory frames. HDLC also specifies three data transfer modes - normal response mode, asynchronous response mode and asynchronous balanced mode. [/SUMMARY]
The document discusses subnetting and provides an example of how to subnet the IP network address 192.168.1.128 into 6 subnets. It explains that subnetting allows a single network number to be shared among multiple physical networks. Each host is configured with an IP address and subnet mask, where the subnet is calculated by performing a bitwise AND of the IP address and subnet mask. The example shows how to determine the subnet mask is 255.255.255.224 when creating 6 subnets, and that each subnet can support up to 30 hosts.
ARP is a protocol that maps IP addresses to MAC addresses. It works by broadcasting an ARP request packet to all devices on the local network segment. The device with the matching IP address responds with its MAC address, allowing the requesting device to send packets directly to the destination MAC address on the local network.
The network layer is responsible for routing packets from the source to destination. The routing algorithm is the piece of software that decides where a packet goes next (e.g., which output line, or which node on a broadcast channel).For connectionless networks, the routing decision is made for each datagram. For connection-oriented networks, the decision is made once, at circuit setup time.
Routing Issues
The routing algorithm must deal with the following issues:
Correctness and simplicity: networks are never taken down; individual parts (e.g., links, routers) may fail, but the whole network should not.
Stability: if a link or router fails, how much time elapses before the remaining routers recognize the topology change? (Some never do..)
Fairness and optimality: an inherently intractable problem. Definition of optimality usually doesn't consider fairness. Do we want to maximize channel usage? Minimize average delay?
When we look at routing in detail, we'll consider both adaptive--those that take current traffic and topology into consideration--and nonadaptive algorithms.
Fast Ethernet increased the bandwidth of standard Ethernet from 10 Mbps to 100 Mbps. It used the same CSMA/CD access method and frame format as standard Ethernet but with some changes to address the higher speed. Fast Ethernet was implemented over twisted pair cables using 100BASE-TX or over fiber optic cables using 100BASE-FX. The increased speed enabled Fast Ethernet to compete with other high-speed LAN technologies of the time like FDDI.
This document describes the sliding window protocol. It discusses key concepts like both the sender and receiver maintaining buffers to hold packets, acknowledgements being sent for every received packet, and the sender being able to send a window of packets before receiving an acknowledgement. It then explains the sender side process of numbering packets and maintaining a sending window. The receiver side maintains a window size of 1 and acknowledges by sending the next expected sequence number. A one bit sliding window protocol acts like stop and wait. Merits include multiple packets being sent without waiting for acknowledgements while demerits include potential bandwidth waste in some situations.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
This document discusses error detection and correction in data transmission. It describes single-bit errors, where one bit is corrupted, and burst errors, where multiple contiguous bits are corrupted. Error detection allows a receiver to detect if errors occurred, while error correction identifies the exact corrupted bits. Redundant bits are added to messages to enable detection and correction. Methods include forward error correction, retransmission, block coding, and convolution coding. Block coding divides messages into blocks with redundant bits added, creating codewords that allow error detection if a codeword is invalid.
Link-state routing protocols use Dijkstra's algorithm to calculate the shortest path to all destinations based on a link-state database containing the full network topology. Each router runs the same algorithm locally to determine the optimal path. Key aspects include link-state advertisements to share connectivity information, the topological database to store network maps, and shortest path first calculations to derive routes. Common link-state protocols are OSPF and IS-IS. They provide fast convergence and scalability but require more resources than distance-vector protocols.
The document discusses the Internet Control Message Protocol (ICMP). ICMP provides error reporting, congestion reporting, and first-hop router redirection. It uses IP to carry its data end-to-end and is considered an integral part of IP. ICMP messages are encapsulated in IP datagrams and are used to report errors in IP datagrams, though some errors may still result in datagrams being dropped without a report. ICMP defines various message types including error messages like destination unreachable and informational messages like echo request and reply.
Go-Back-N (GBN) is an ARQ protocol that allows a sender to transmit multiple frames before receiving an acknowledgement. The sender maintains a window of size N, meaning it can transmit N frames before waiting for a response. The receiver window is always size 1, acknowledging frames individually. If a frame times out without an ACK, the sender retransmits that frame and all subsequent frames in the window. GBN improves efficiency over stop-and-wait by allowing transmission of multiple frames while reducing waiting time at the sender.
Relational algebra is a procedural query language used to manipulate relations in a relational database. It consists of operators like select, project, join, union, and set difference. SQL is based on the concepts of relational algebra. Relational algebra expressions specify a sequence of operators to apply to relations in order to retrieve the desired data from the database. Some key operators include selection to filter tuples, projection to select attributes, and join to combine tuples from two relations based on a join condition.
This document summarizes key concepts from Chapter 14 of the textbook "Database System Concepts, 6th Ed." including:
1) A transaction is a unit of program execution that accesses and updates data items. For integrity, transactions must have ACID properties: atomicity, consistency, isolation, and durability.
2) Concurrency control ensures serializable execution of concurrent transactions to maintain consistency. Schedules must be conflict serializable and recoverable.
3) SQL supports transactions and different isolation levels to balance consistency and concurrency. The default isolation level is usually serializable but some systems allow weaker isolation.
This document provides an overview of the Domain Name System (DNS) including its hierarchical structure, services, and protocol. DNS acts as a distributed database that maps hostnames to IP addresses and vice versa. It is implemented through a global hierarchy of root servers, top-level domain servers like .com and .edu, and authoritative name servers for each organization. DNS uses a query/response system to look up mappings in a recursive or iterative process. Caching improves efficiency.
The document discusses database normalization. It defines normalization as a process that organizes data into tables to eliminate redundancies and anomalies like inconsistent data changes. The document then covers various normal forms including 1st, 2nd, 3rd normal form and Boyce-Codd normal form. It provides examples of relations and how they can be normalized to remove functional dependencies and anomalies to satisfy each normal form's rules.
Each month, join us as we highlight and discuss hot topics ranging from the future of higher education to wearable technology, best productivity hacks and secrets to hiring top talent. Upload your SlideShares, and share your expertise with the world!
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SlideShare is a global platform for sharing presentations, infographics, videos and documents. It has over 18 million pieces of professional content uploaded by experts like Eric Schmidt and Guy Kawasaki. The document provides tips for setting up an account on SlideShare, uploading content, optimizing it for searchability, and sharing it on social media to build an audience and reputation as a subject matter expert.
This document provides an overview of link layer and LAN concepts. It introduces error detection and correction, multiple access protocols, LAN addressing using ARP, Ethernet standards and frame structure, and switching technology. Ethernet switches allow for multiple simultaneous transmissions by connecting each host to its own dedicated port, eliminating collisions and creating independent collision domains. This increases throughput over shared-medium Ethernet topologies.
This document provides a summary of key concepts about switches and the Address Resolution Protocol (ARP) at the link layer of computer networks:
- Switches operate at the link layer, selectively forwarding frames to the correct outgoing link based on the frame's MAC address. Switches learn MAC addresses and their associated ports through a self-learning process.
- ARP is used to dynamically map IP addresses to MAC addresses when two hosts are on the same local area network (LAN). When a host wants to send to an IP address, it first broadcasts an ARP request. The host with that IP responds with its MAC address.
- For hosts on different LANs, the sending host uses ARP to get the MAC address
The document discusses link layer concepts including link layer addressing, MAC addresses, ARP, Ethernet frames, CSMA/CD, hubs, and switches. It explains that MAC addresses are used to deliver frames within a local area network, while IP addresses are used between networks. ARP is used to map IP addresses to MAC addresses on the same network. Ethernet uses CSMA/CD for media access and frames include source and destination MAC addresses. Hubs operate at the physical layer while switches operate at the data link layer and can reduce collisions by isolating segments.
The document provides an introduction to the OSI 7 layer model and describes the data link layer in detail. It discusses the basic design principles of the data link layer, including how it provides communication between two directly connected nodes and deals with problems like errors. It also describes how real networks like Ethernet work at the data link layer and provides a Wireshark demo to show live network packet data and decoding.
Medium Access PROTOCOL b yENGR. FAWAD KHAN UET BANNU KP PAKISTANirfan sami
1. The document discusses medium access control (MAC) protocols for shared broadcast links at the link layer. It covers three main classes of MAC protocols: channel partitioning, random access, and "taking turns" protocols.
2. Channel partitioning protocols like TDMA and FDMA divide the channel into time or frequency slots and allocate slots to nodes. Random access protocols like ALOHA, CSMA, and CSMA/CD allow nodes to transmit randomly and include mechanisms to detect and handle collisions. "Taking turns" protocols such as polling and token passing coordinate channel access by having nodes take turns transmitting.
3. The ideal MAC protocol allows single or multiple nodes to transmit at the maximum channel rate, is fully decentralized, requires
This chapter begins an examination of the flow of traffic in a modern network. It
examines some of the current network design models and the way LAN switches
build forwarding tables and use the MAC address information to efficiently
switch data between hosts.
This document discusses the link layer and local area networks. It begins with an introduction to link layer services including framing, link access, reliable delivery, flow control, and error detection and correction. It then covers topics like multiple access protocols, including random access protocols like ALOHA and CSMA, and controlled access protocols. Local area network technologies are discussed next, focusing on Ethernet, switches, and addressing protocols like ARP. The document concludes with sections on link virtualization using MPLS and data center networking.
The document provides an overview of the link layer. It discusses the goals and services of the link layer, including error detection, correction, and sharing access to broadcast channels through multiple access protocols. It describes various link layer technologies like Ethernet, switches, and VLANs. It also covers topics like link layer addressing using MAC addresses, the Address Resolution Protocol (ARP) for mapping IP addresses to MAC addresses, and examples of multiple access protocols including Carrier Sense Multiple Access with Collision Detection (CSMA/CD) used in Ethernet networks.
This course describes the basic networking elements and how they are used in practice. The course covers:
The evolution and principles of networking;
The basic notions used in this domain;
Types of equipment;
Description and general information of basic networking protocols.
The practical examples provide configuration commands, packet captures and a real feel of how to build a simple network
The course attendees will be encouraged to show their understanding by answering questions and debating the issues and solutions that they might have encountered when working with networks.
The document provides an overview of Ethernet networking fundamentals, including:
1) It defines Ethernet as a standard communications method for building local area networks using networking devices, cables, and infrastructure equipment.
2) It describes the OSI model and how Ethernet operates at the physical and data link layers.
3) It explains MAC addressing for unicast, multicast, and broadcast traffic and how switches use MAC addresses to direct traffic to specific ports.
Gourav Salla presented on Address Resolution Protocol (ARP). ARP is used to map IP addresses to MAC addresses so devices can communicate on a local network. It works by broadcasting an ARP request packet containing the target IP address. The device with that IP address responds with its MAC address. This address resolution allows packets for that destination to be sent directly using layer 2 addressing. ARP caches entries to avoid repeating the lookup for frequent communication between devices on the same subnet.
This video forms part of the showcase event held by the Intelligent Airport (TINA) project: http://intelligentairport.org.uk.
The University of Cambridge Computer Laboratory developed a new scalable network architecture, MOOSE (Multi-level Origin-Organised Scalable Ethernet).
This document contains a 10 question multiple choice quiz about topics in Chapter 6 of the textbook "Computer Networking: A Top-Down Approach". The questions cover topics such as characteristics of channel partitioning protocols, probabilities in slotted ALOHA, services provided by Ethernet, behaviors of nodes using CSMA/CD, probabilities after collisions in CSMA/CD, topologies of Ethernet LANs, frame contents for switches, the switch poisoning attack, and properties of cut-through switches.
This document contains 21 multiple choice questions and answers from the CCNA 1 Chapter 9 exam on network fundamentals. The questions cover topics like Ethernet protocols, data encapsulation, MAC addressing, collision detection using CSMA/CD, and Ethernet switching fundamentals.
The document discusses several key functions and design goals of the network layer in internet architecture. It covers routing algorithms like distance vector and link state routing, as well as routing protocols like RIP. It also provides an overview of the TCP/IP protocol stack and some of its core components like IP, ICMP, TCP and UDP.
This document discusses different types of random access MAC protocols: Slotted Aloha, Pure Aloha, CSMA, and CSMA/CD. It also covers taking turns MAC protocols like polling and token passing. Key points include:
- Slotted Aloha divides time into slots and stations transmit at slot boundaries to avoid collisions. Optimal transmission probability is 1/N where N is number of stations.
- Pure Aloha does not use slots, increasing collision probability and reducing throughput.
- CSMA involves listening before transmitting to avoid collisions but they can still occur if two stations sense the channel idle simultaneously.
- CSMA/CD adds collision detection, allowing transmitters to abort
The document summarizes key concepts about TCP/IP from Chapter 3 of a CCNA guide. It discusses the origins of TCP/IP from projects by DARPA and the inclusion of TCP/IP in UNIX. It also describes the four layers of the TCP/IP model including the application, transport, internet, and network interface layers. Finally, it provides an overview of common protocols at each layer such as TCP, UDP, IP, ARP, and how packets are transmitted between hosts and routers.
This document summarizes key concepts about IP, packet forwarding, and switch fabrics. It discusses how IP provides connectionless delivery of packets using headers that include source and destination addresses. Packets are forwarded based on their destination address, and routers maintain forwarding tables. Switch fabrics must deliver packets from input to output ports, and approaches include shared bus, crossbar, and self-routing switches like Banyan networks. Bisection bandwidth measures the minimum bandwidth between equally divided sets of ports in a network.
Lecture 25 Link Layer - Error detection and Multiple Access.pptxHanzlaNaveed1
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This document discusses memory management techniques used in operating systems, including:
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- Address binding from source code to executable addresses at different stages.
- The memory management unit (MMU) that maps virtual to physical addresses using base/limit registers.
- Segmentation architecture that divides memory into logical segments like code, data, stack, heap.
This document summarizes key concepts from Chapter 7 of the textbook Operating System Concepts by Silberschatz, Galvin and Gagne. It discusses deadlocks in computer systems, including their characterization and conditions for their occurrence. It also describes several approaches for handling deadlocks, such as prevention, avoidance, detection and recovery methods. The resource allocation graph and banker's algorithm are presented as techniques for deadlock avoidance when multiple instances of resources are present.
Pipelining is a technique where the instruction execution process is divided into multiple stages that can operate in parallel. This allows subsequent instructions to begin processing before previous ones have finished. For example, with laundry, pipelining allows washing, drying, and folding different loads simultaneously to complete all the laundry faster. In processors, pipelining overlaps the stages of instruction fetch, decode, execute, and writeback to improve throughput. While pipelining improves performance, it can introduce hazards like structural, data, and control hazards that must be addressed.
1. The document discusses different types of information needed at various levels of management, including operational, tactical, strategic, and statutory information.
2. It also describes the different levels of management in a hierarchy and the types of information required at each level, from highly detailed reports needed by line managers to condensed strategic information for top managers.
3. The key types of information systems are also outlined, including business data processing systems, management information systems, and decision support systems.
The document outlines the 9 steps in the systems analysis and design life cycle: 1) requirements determination, 2) requirements specification, 3) feasibility analysis, 4) final specifications, 5) hardware study, 6) system design, 7) system implementation, 8) system evaluation, and 9) system modification. It then provides details on the tasks involved in each step and discusses the roles, attributes, and tools used by systems analysts.
This document discusses various methods for gathering information during the requirements gathering phase of a software project. It describes strategies like identifying information sources, developing methods to obtain information from sources, and using organizational flow models. Key information sources include users, forms, manuals, reports, and existing systems. Important techniques involve interviews with various stakeholders, using organizational charts to identify important people, and gathering both qualitative and quantitative data. Tools for gathering information include reviewing literature and forms, on-site observation, interviews using structured and unstructured techniques, and questionnaires.
The document discusses managing information systems projects. It defines key project management terms like project, project manager, and deliverable. It explains the importance of project management in meeting expectations and constraints. The project life cycle includes initiation, planning, execution, and closeout. Techniques for scheduling projects are described, like Gantt charts, network diagrams, PERT calculations, and critical path scheduling. Critical path scheduling identifies the shortest path to complete a project. Project management software can help plan and track projects.
This document discusses feasibility analysis for a proposed hostel information system. It identifies deficiencies in the current manual system, formulates goals and sub-goals to address the deficiencies, and evaluates three alternative solutions: 1) improving the manual system, 2) using a periodic update PC system, and 3) an online system with server and clients. It determines that solution B of using a PC system is technically and operationally feasible. A cost-benefit analysis shows that the estimated costs of 130,000 rupees would be recovered within 4-5 months due to savings from reduced inventory, early payments, and other benefits. An executive summary and system proposal structure are also outlined.
This document discusses project identification and selection processes. It describes corporate strategic planning and information systems planning, noting that IS planning can help identify projects that align with business objectives. Projects may be identified through top-down or bottom-up processes. IS planning involves describing the current and target situations and developing a transition plan. The document also discusses electronic commerce applications like the internet, intranets, and extranets.
This chapter discusses automated tools for systems development, known as Computer-Aided Software Engineering (CASE) tools. It describes the different categories of CASE tools, including upper CASE, lower CASE, cross life-cycle CASE, and visual development tools. A key component is the CASE repository, which centrally stores information generated throughout the systems development life cycle, including diagrams, forms, reports, and code. The repository includes an information repository and data dictionary. CASE tools aim to improve productivity and quality by facilitating integration and automation across the development process.
This document discusses the skills required of a systems analyst, including analytical skills, technical skills, management skills, and interpersonal skills. It focuses on analytical skills, describing four key areas: systems thinking, organizational knowledge, problem identification, and problem analysis and solving. Systems thinking involves understanding systems concepts like decomposition, modularity, coupling, and cohesion. Systems analysts must be able to represent information systems as systems using tools like data flow diagrams. Organizational knowledge of how an organization works is also important.
This document provides information about a System Analysis and Design course offered by Daffodil International University. The 3-credit, 3-hour per week course focuses on applying information technologies to the system development life cycle including methodologies, analysis, design, and implementation. It aims to teach students how to design and deliver information systems to meet business needs utilizing techniques like requirements documentation. The textbook is Modern Systems Analysis and Design by Hoffer, George, and Valacich which covers topics like system types, the development process, and roles in system development projects.
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Drink plenty of water, eat fruits and vegetables daily, and have a healthy breakfast with carbohydrates and protein. Eat smaller, more frequent meals throughout the day and aim for variety with different foods and colors. Also, get regular exercise through walking, using stairs, and daily activities while prioritizing good sleep and a clean environment.
The document provides tips for effective living and achieving balance. It emphasizes finding balance between priorities like parents, self, country, and passion. Some key tips include knowing your limits within 24 hours per day, doing what you love, maintaining simplicity, believing in honesty and hard work, proper health habits, cultivating spirituality, planning in advance, having good relationships, engaging in hobbies, and learning to be satisfied. The overall message is achieving balance across priorities through time management, passion-based work, spiritual fulfillment, relationships and hobbies.
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International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
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of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
CHINA’S GEO-ECONOMIC OUTREACH IN CENTRAL ASIAN COUNTRIES AND FUTURE PROSPECTjpsjournal1
The rivalry between prominent international actors for dominance over Central Asia's hydrocarbon
reserves and the ancient silk trade route, along with China's diplomatic endeavours in the area, has been
referred to as the "New Great Game." This research centres on the power struggle, considering
geopolitical, geostrategic, and geoeconomic variables. Topics including trade, political hegemony, oil
politics, and conventional and nontraditional security are all explored and explained by the researcher.
Using Mackinder's Heartland, Spykman Rimland, and Hegemonic Stability theories, examines China's role
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china’s geo economic outreach in central Asian countries and its future prospect. China is thriving in trade,
pipeline politics, and winning states, according to this study, thanks to important instruments like the
Shanghai Cooperation Organisation and the Belt and Road Economic Initiative. According to this study,
China is seeing significant success in commerce, pipeline politics, and gaining influence on other
governments. This success may be attributed to the effective utilisation of key tools such as the Shanghai
Cooperation Organisation and the Belt and Road Economic Initiative.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
2. Link Layer 5-2
MAC addresses and ARP
32-bit IP address:
network-layer address for interface
used for layer 3 (network layer) forwarding
MAC (or LAN or physical or Ethernet) address:
function: used ‘locally” to get frame from one interface to
another physically-connected interface (same network, in IP-
addressing sense)
48 bit MAC address (for most LANs) burned in NIC
ROM, also sometimes software settable
e.g.: 1A-2F-BB-76-09-AD
hexadecimal (base 16) notation
(each “number” represents 4 bits)
3. Link Layer 5-3
LAN addresses and ARP
each adapter on LAN has unique LAN address
adapter
1A-2F-BB-76-09-AD
58-23-D7-FA-20-B0
0C-C4-11-6F-E3-98
71-65-F7-2B-08-53
LAN
(wired or
wireless)
4. Link Layer 5-4
LAN addresses (more)
MAC address allocation administered by IEEE
manufacturer buys portion of MAC address space
(to assure uniqueness)
analogy:
MAC address: like Social Security Number
IP address: like postal address
MAC flat address ➜ portability
can move LAN card from one LAN to another
IP hierarchical address not portable
address depends on IP subnet to which node is
attached
5. Link Layer 5-5
ARP: address resolution protocol
ARP table: each IP node (host,
router) on LAN has table
IP/MAC address
mappings for some LAN
nodes:
< IP address; MAC address; TTL>
TTL (Time To Live):
time after which address
mapping will be
forgotten (typically 20
min)
Question: how to determine
interface’s MAC address,
knowing its IP address?
1A-2F-BB-76-09-AD
58-23-D7-FA-20-B0
0C-C4-11-6F-E3-98
71-65-F7-2B-08-53
LAN
137.196.7.23
137.196.7.78
137.196.7.14
137.196.7.88
6. Link Layer 5-6
ARP protocol: same LAN
A wants to send datagram
to B
B’s MAC address not in A’s
ARP table.
A broadcasts ARP query
packet, containing B's IP
address
dest MAC address = FF-FF-
FF-FF-FF-FF
all nodes on LAN receive
ARP query
B receives ARP packet,
replies to A with its (B's)
MAC address
frame sent to A’s MAC
address (unicast)
A caches (saves) IP-to-
MAC address pair in its
ARP table until
information becomes old
(times out)
soft state: information that
times out (goes away)
unless refreshed
ARP is “plug-and-play”:
nodes create their ARP
tables without intervention
from net administrator
7. Link Layer 5-7
walkthrough: send datagram from A to B via R
focus on addressing – at IP (datagram) and MAC layer (frame)
assume A knows B’s IP address
assume A knows IP address of first hop router, R (how?)
assume A knows R’s MAC address (how?)
Addressing: routing to another LAN
R
1A-23-F9-CD-06-9B
222.222.222.220
111.111.111.110
E6-E9-00-17-BB-4BCC-49-DE-D0-AB-7D
111.111.111.112
111.111.111.111
74-29-9C-E8-FF-55
A
222.222.222.222
49-BD-D2-C7-56-2A
222.222.222.221
88-B2-2F-54-1A-0F
B
13. Link Layer 5-13
Ethernet
“dominant” wired LAN technology:
cheap $20 for NIC
first widely used LAN technology
simpler, cheaper than token LANs and ATM
kept up with speed race: 10 Mbps – 10 Gbps
Metcalfe’s Ethernet sketch
14. Link Layer 5-14
Ethernet: physical topology
bus: popular through mid 90s
all nodes in same collision domain (can collide with each
other)
star: prevails today
active switch in center
each “spoke” runs a (separate) Ethernet protocol (nodes
do not collide with each other)
switch
bus: coaxial cable
star
15. Link Layer 5-15
Ethernet frame structure
sending adapter encapsulates IP datagram (or other
network layer protocol packet) in Ethernet frame
preamble:
7 bytes with pattern 10101010 followed by one
byte with pattern 10101011
used to synchronize receiver, sender clock rates
dest.
address
source
address
data
(payload) CRCpreamble
type
16. Link Layer 5-16
Ethernet frame structure (more)
addresses: 6 byte source, destination MAC addresses
if adapter receives frame with matching destination
address, or with broadcast address (e.g. ARP packet), it
passes data in frame to network layer protocol
otherwise, adapter discards frame
type: indicates higher layer protocol (mostly IP but
others possible, e.g., Novell IPX, AppleTalk)
CRC: cyclic redundancy check at receiver
error detected: frame is dropped
dest.
address
source
address
data
(payload) CRCpreamble
type
17. Link Layer 5-17
Ethernet: unreliable, connectionless
connectionless: no handshaking between sending and
receiving NICs
unreliable: receiving NIC doesnt send acks or nacks
to sending NIC
data in dropped frames recovered only if initial
sender uses higher layer rdt (e.g., TCP), otherwise
dropped data lost
Ethernet’s MAC protocol: unslotted CSMA/CD wth
binary backoff
18. Link Layer 5-18
Ethernet switch
link-layer device: takes an active role
store, forward Ethernet frames
examine incoming frame’s MAC address,
selectively forward frame to one-or-more
outgoing links when frame is to be forwarded on
segment, uses CSMA/CD to access segment
transparent
hosts are unaware of presence of switches
plug-and-play, self-learning
switches do not need to be configured
19. Link Layer 5-19
Switch: multiple simultaneous transmissions
hosts have dedicated, direct
connection to switch
switches buffer packets
Ethernet protocol used on each
incoming link, but no collisions;
full duplex
each link is its own collision
domain
switching: A-to-A’ and B-to-B’
can transmit simultaneously,
without collisions switch with six interfaces
(1,2,3,4,5,6)
A
A’
B
B’ C
C’
1 2
345
6
20. Link Layer 5-20
Switch forwarding table
Q: how does switch know A’
reachable via interface 4, B’
reachable via interface 5?
switch with six interfaces
(1,2,3,4,5,6)
A
A’
B
B’ C
C’
1 2
345
6 A: each switch has a switch
table, each entry:
(MAC address of host, interface to
reach host, time stamp)
looks like a routing table!
Q: how are entries created,
maintained in switch table?
something like a routing protocol?
21. A
A’
B
B’ C
C’
1 2
345
6
Link Layer 5-21
Switch: self-learning
switch learns which hosts
can be reached through
which interfaces
when frame received,
switch “learns”
location of sender:
incoming LAN segment
records sender/location
pair in switch table
A A’
Source: A
Dest: A’
MAC addr interface TTL
Switch table
(initially empty)
A 1 60
22. A
A’
B
B’ C
C’
1 2
345
6
Link Layer 5-22
Self-learning, forwarding: example
A A’
Source: A
Dest: A’
MAC addr interface TTL
switch table
(initially empty)
A 1 60
A A’A A’A A’A A’A A’
frame destination, A’,
locaton unknown: flood
A’ A
destination A location
known:
A’ 4 60
selectively send
on just one link
23. Link Layer 5-23
Interconnecting switches
switches can be connected together
Q: sending from A to G - how does S1 know to
forward frame destined to F via S4 and S3?
A: self learning! (works exactly the same as in single-
switch case!)
A
B
S1
C D
E
F
S2
S4
S3
H
I
G
24. Link Layer 5-24
Self-learning multi-switch example
Suppose C sends frame to I, I responds to C
Q: show switch tables and packet forwarding in S1, S2, S3, S4
A
B
S1
C D
E
F
S2
S4
S3
H
I
G
26. Link Layer 5-26
Switches vs. routers
both are store-and-forward:
routers: network-layer
devices (examine network-
layer headers)
switches: link-layer devices
(examine link-layer headers)
both have forwarding tables:
routers: compute tables using
routing algorithms, IP
addresses
switches: learn forwarding
table using flooding, learning,
MAC addresses
application
transport
network
link
physical
network
link
physical
link
physical
switch
datagram
application
transport
network
link
physical
frame
frame
frame
datagram
27. Link Layer 5-27
VLANs: motivation
consider:
CS user moves office to
EE, but wants connect to
CS switch?
single broadcast domain:
all layer-2 broadcast
traffic (ARP, DHCP,
unknown location of
destination MAC
address) must cross
entire LAN
security/privacy,
efficiency issues
Computer
Science Electrical
Engineering
Computer
Engineering
28. Link Layer 5-28
VLANs
port-based VLAN: switch ports
grouped (by switch management
software) so that single physical
switch ……
switch(es) supporting
VLAN capabilities can
be configured to
define multiple virtual
LANS over single
physical LAN
infrastructure.
Virtual Local
Area Network
1
8
9
16102
7
…
Electrical Engineering
(VLAN ports 1-8)
Computer Science
(VLAN ports 9-15)
15
…
Electrical Engineering
(VLAN ports 1-8)
…
1
82
7 9
1610
15
…
Computer Science
(VLAN ports 9-16)
… operates as multiple virtual switches
29. Link Layer 5-29
Port-based VLAN
1
8
9
16102
7
…
Electrical Engineering
(VLAN ports 1-8)
Computer Science
(VLAN ports 9-15)
15
…
traffic isolation: frames to/from
ports 1-8 can only reach ports
1-8
can also define VLAN based on
MAC addresses of endpoints,
rather than switch port
dynamic membership: ports
can be dynamically assigned
among VLANs
router
forwarding between VLANS: done via
routing (just as with separate
switches)
in practice vendors sell combined
switches plus routers
30. Link Layer 5-30
VLANS spanning multiple switches
trunk port: carries frames between VLANS defined over
multiple physical switches
frames forwarded within VLAN between switches can’t be vanilla
802.1 frames (must carry VLAN ID info)
802.1q protocol adds/removed additional header fields for frames
forwarded between trunk ports
1
8
9
102
7
…
Electrical Engineering
(VLAN ports 1-8)
Computer Science
(VLAN ports 9-15)
15
…
2
73
Ports 2,3,5 belong to EE VLAN
Ports 4,6,7,8 belong to CS VLAN
5
4 6 816
1
31. Link Layer 5-31
Synthesis: a day in the life of a web request
journey down protocol stack complete!
application, transport, network, link
putting-it-all-together: synthesis!
goal: identify, review, understand protocols (at all
layers) involved in seemingly simple scenario:
requesting www page
scenario: student attaches laptop to campus network,
requests/receives www.google.com
32. Link Layer 5-32
A day in the life: scenario
Comcast network
68.80.0.0/13
Google’s network
64.233.160.0/1964.233.169.105
web server
DNS server
school network
68.80.2.0/24
web page
browser
33. router
(runs DHCP)
Link Layer 5-33
A day in the life… connecting to the Internet
connecting laptop needs to
get its own IP address, addr
of first-hop router, addr of
DNS server: use DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCPDHCP
DHCP request encapsulated
in UDP, encapsulated in IP,
encapsulated in 802.3
Ethernet
Ethernet frame broadcast
(dest: FFFFFFFFFFFF) on
LAN, received at router
running DHCP server
Ethernet demuxed to IP
demuxed, UDP demuxed to
DHCP
34. router
(runs DHCP)
Link Layer 5-34
DHCP server formulates
DHCP ACK containing
client’s IP address, IP
address of first-hop router
for client, name & IP
address of DNS server
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
DHCP
encapsulation at DHCP
server, frame forwarded
(switch learning) through LAN,
demultiplexing at client
Client now has IP address, knows name & addr of DNS
server, IP address of its first-hop router
DHCP client receives
DHCP ACK reply
A day in the life… connecting to the Internet
35. router
(runs DHCP)
Link Layer 5-35
A day in the life… ARP (before DNS, before HTTP)
before sending HTTP request, need
IP address of www.google.com:
DNS
DNS
UDP
IP
Eth
Phy
DNS
DNS
DNS
DNS query created, encapsulated in UDP,
encapsulated in IP, encapsulated in Eth. To
send frame to router, need MAC address of
router interface: ARP
ARP query broadcast, received by
router, which replies with ARP
reply giving MAC address of
router interface
client now knows MAC address
of first hop router, so can now
send frame containing DNS
query
ARP query
Eth
Phy
ARP
ARP
ARP reply
36. router
(runs DHCP)
Link Layer 5-36
DNS
UDP
IP
Eth
Phy
DNS
DNS
DNS
DNS
DNS
IP datagram containing DNS
query forwarded via LAN
switch from client to 1st
hop
router
IP datagram forwarded from
campus network into comcast
network, routed (tables created
by RIP, OSPF, IS-IS and/or BGP
routing protocols) to DNS server
demux’ed to DNS server
DNS server replies to client
with IP address of
www.google.com
Comcast network
68.80.0.0/13
DNS server
DNS
UDP
IP
Eth
Phy
DNS
DNS
DNS
DNS
A day in the life… using DNS
37. router
(runs DHCP)
Link Layer 5-37
A day in the life…TCP connection carrying HTTP
HTTP
TCP
IP
Eth
Phy
HTTP
to send HTTP request,
client first opens TCP socket
to web server
TCP SYN segment (step 1 in 3-
way handshake) inter-domain
routed to web server
TCP connection established!64.233.169.105
web server
SYN
SYN
SYN
SYN
TCP
IP
Eth
Phy
SYN
SYN
SYN
SYNACK
SYNACK
SYNACK
SYNACK
SYNACK
SYNACK
SYNACK
web server responds with TCP
SYNACK (step 2 in 3-way
handshake)
38. router
(runs DHCP)
Link Layer 5-38
A day in the life… HTTP request/reply
HTTP
TCP
IP
Eth
Phy
HTTP
HTTP request sent into TCP
socket
IP datagram containing HTTP
request routed to
www.google.com
IP datagram containing HTTP reply
routed back to client64.233.169.105
web server
HTTP
TCP
IP
Eth
Phy
web server responds with
HTTP reply (containing web
page)
HTTP
HTTP
HTTPHTTP
HTTP
HTTP
HTTP
HTTP
HTTP
HTTP
HTTP
HTTP
HTTP
web page finally (!!!) displayed