This document provides an overview of the key concepts in the network layer data plane, including:
- The goals and functions of the network layer data plane and control plane.
- The basic components and operations of a router, including input ports, switching fabrics, output ports, and buffer management.
- Forwarding and routing as the two key network layer functions.
- IP as the core network layer protocol used in the Internet, including its addressing and packet format.
- Generalized forwarding and software-defined networking approaches.
- Common queuing, scheduling, and buffer management techniques used within routers.
This document provides an overview of the network layer and how routers function. It discusses the data plane of routers, including input and output ports, switching fabrics, buffer management, scheduling, and forwarding. It also covers the Internet Protocol (IP) including the datagram format, addressing, and subnets. Key concepts explained are longest prefix matching, input and output port queuing, switching fabrics like bus, memory and interconnection networks, and scheduling algorithms like priority, round robin, and weighted fair queueing.
This document provides an overview of slides for a chapter on the network layer data plane from the textbook "Computer Networking: A Top-Down Approach". The slides cover topics including network layer services, forwarding versus routing, router architecture, addressing, and longest prefix matching. The author provides the slides freely for educational use and asks that their source and copyright be acknowledged.
- The document is a chapter from a textbook on computer networking that discusses the network layer. It covers topics like virtual circuit networks, datagram networks, the operation of routers, IP, routing algorithms, and routing in the Internet.
- Routers examine header fields to forward packets to the appropriate output port based on the destination address and routing tables. Routing algorithms determine the path packets take between source and destination.
- Virtual circuit networks use call setup and connection state in routers to provide guaranteed services, while datagram networks like the Internet forward packets based only on destination addresses for simple operation.
This document discusses various topics relating to the network layer, including:
1. The network layer transports data segments between hosts by encapsulating them into datagrams and routing them through routers and links.
2. Routers examine header fields to determine how to forward datagrams to their destination, either based on destination address or other header values.
3. The network layer provides forwarding to move packets between router interfaces and routing to determine the path between source and destination. Control planes implement routing algorithms while data planes perform packet forwarding.
This document provides an overview of the key topics covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach" including:
- The network layer principles of forwarding versus routing, how routers work, routing algorithms, and scaling techniques.
- Network layer service models including best effort, guaranteed delivery, and quality of service guarantees.
- Virtual circuit and datagram networks and how connections are established in each.
- The internal components and functions of routers including routing algorithms, forwarding tables, switching fabrics, input/output port queuing.
- The Internet network layer protocols including IP for addressing, datagrams, and fragmentation/reassembly, ICMP for error reporting, and routing protocols.
This document provides an overview and outline of topics to be covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach". The chapter will cover the network layer data plane, including how routers work, IP as an internet protocol, and generalized forwarding. It outlines key concepts like forwarding, routing, and the difference between the data and control planes. It also summarizes the internal components and functions of a router, like lookup and switching fabrics.
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.
This document provides an overview and outline of topics covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach". The chapter focuses on the network layer and covers data plane functions like forwarding, routing, and how routers work. It also discusses control plane functions and routing protocols. The key topics covered include IP addressing, fragmentation, and an overview of the Internet network layer protocol stack.
This document provides an overview of the network layer and how routers function. It discusses the data plane of routers, including input and output ports, switching fabrics, buffer management, scheduling, and forwarding. It also covers the Internet Protocol (IP) including the datagram format, addressing, and subnets. Key concepts explained are longest prefix matching, input and output port queuing, switching fabrics like bus, memory and interconnection networks, and scheduling algorithms like priority, round robin, and weighted fair queueing.
This document provides an overview of slides for a chapter on the network layer data plane from the textbook "Computer Networking: A Top-Down Approach". The slides cover topics including network layer services, forwarding versus routing, router architecture, addressing, and longest prefix matching. The author provides the slides freely for educational use and asks that their source and copyright be acknowledged.
- The document is a chapter from a textbook on computer networking that discusses the network layer. It covers topics like virtual circuit networks, datagram networks, the operation of routers, IP, routing algorithms, and routing in the Internet.
- Routers examine header fields to forward packets to the appropriate output port based on the destination address and routing tables. Routing algorithms determine the path packets take between source and destination.
- Virtual circuit networks use call setup and connection state in routers to provide guaranteed services, while datagram networks like the Internet forward packets based only on destination addresses for simple operation.
This document discusses various topics relating to the network layer, including:
1. The network layer transports data segments between hosts by encapsulating them into datagrams and routing them through routers and links.
2. Routers examine header fields to determine how to forward datagrams to their destination, either based on destination address or other header values.
3. The network layer provides forwarding to move packets between router interfaces and routing to determine the path between source and destination. Control planes implement routing algorithms while data planes perform packet forwarding.
This document provides an overview of the key topics covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach" including:
- The network layer principles of forwarding versus routing, how routers work, routing algorithms, and scaling techniques.
- Network layer service models including best effort, guaranteed delivery, and quality of service guarantees.
- Virtual circuit and datagram networks and how connections are established in each.
- The internal components and functions of routers including routing algorithms, forwarding tables, switching fabrics, input/output port queuing.
- The Internet network layer protocols including IP for addressing, datagrams, and fragmentation/reassembly, ICMP for error reporting, and routing protocols.
This document provides an overview and outline of topics to be covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach". The chapter will cover the network layer data plane, including how routers work, IP as an internet protocol, and generalized forwarding. It outlines key concepts like forwarding, routing, and the difference between the data and control planes. It also summarizes the internal components and functions of a router, like lookup and switching fabrics.
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.
This document provides an overview and outline of topics covered in Chapter 4 of the textbook "Computer Networking: A Top Down Approach". The chapter focuses on the network layer and covers data plane functions like forwarding, routing, and how routers work. It also discusses control plane functions and routing protocols. The key topics covered include IP addressing, fragmentation, and an overview of the Internet network layer protocol stack.
This document discusses the network layer and IP protocol. It begins by explaining the key functions of the network layer, including forwarding, routing, and connection setup in some network architectures. It then explains the differences between virtual circuit and datagram networks, as well as the forwarding and routing processes. The document outlines the chapter and describes the IP datagram format and functions of the IP, ICMP, and routing protocols. It also provides details about router architecture and functions.
The document provides an overview of the network layer chapter from the textbook "Computer Networking: A Top Down Approach". It outlines the key topics covered in the chapter including network layer service models, how routers work, routing algorithms, IP addressing, and routing protocols used in the Internet. The chapter goals are to understand the principles of the network layer and how these concepts are implemented in the Internet.
The document summarizes key aspects of network layer functionality in computer networks. It discusses the differences between virtual circuit and datagram networks, and how they provide different types of connection-oriented and connectionless services. It also describes the basic functions of routers in forwarding packets using destination addresses and routing algorithms to determine optimal paths through the network.
computer organizational architecture lecture 14 william starliin sahil shama
This document discusses the network layer and key concepts such as virtual circuits, datagrams, forwarding, and routing. It describes the differences between virtual circuit and datagram networks, and how routers work by examining packet headers to forward datagrams using routing algorithms and forwarding tables. The goals of the network layer are to transport segments between hosts using network layer protocols in hosts and routers.
The document provides information on the TCP/IP protocol suite including:
- TCP/IP has 4 layers (Application, Transport, Network, Data Link) compared to OSI's 7 layers.
- Common application layer protocols include FTP, Telnet, SMTP, HTTP.
- Transport layer protocols are TCP and UDP which provide reliable and unreliable data transmission.
- Network layer protocols like IP, ARP, and ICMP handle routing and addressing.
- Layers communicate through encapsulation where each layer adds its own header to protocol data units.
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 summarizes key concepts about the network layer:
1) The network layer is responsible for transporting data segments from sending to receiving hosts by encapsulating segments into datagrams. Routers examine header fields to forward datagrams.
2) The network layer provides three key functions - forwarding, routing, and call setup. Forwarding moves packets through routers, routing determines the path between source and destination, and call setup establishes connections before data flows.
3) The Internet's network layer uses IP to define addressing and datagram format. Routing protocols determine paths and ICMP reports errors. This allows connectionless and best-effort delivery across media.
The document discusses computer networks and network protocols. It begins with an introduction to network protocols and the Internet protocols. It then provides definitions and explanations of communication protocols, including addressing, transmission modes, and error detection/recovery techniques. It lists and describes common network protocols like TCP/IP, routing protocols, FTP, SMTP, and more. It also discusses the OSI model layers, TCP/IP protocol suite, data encapsulation, protocol data units, protocol assignments to layers, and addresses at each layer.
The network layer is responsible for transporting data segments from the sending host to the receiving host. Key functions of the network layer include forwarding, which moves packets through routers, and routing, which determines the path between source and destination. There are two main network architectures: connection-oriented networks using virtual circuits and connectionless networks using datagrams. Routers examine packet headers to perform forwarding and contain input/output ports connected by a switching fabric, as well as a routing processor that maintains routing tables.
09 Systems Software Programming-Network Programming.pptxKushalSrivastava23
This document discusses client-server networking and the TCP/IP protocol stack.
It begins by explaining the client-server model and how servers manage resources for clients. It then describes the layers of a computer network from SAN to WAN. The document discusses how Ethernet segments, bridges, and routers connect local area networks. It introduces the concepts of internet protocols and how they provide naming and delivery of packets across incompatible networks. The roles of IP, TCP, UDP, and sockets in client-server communication are summarized. Finally, it provides examples of functions like getaddrinfo() and getnameinfo() for host and service name resolution.
The network layer routes packets between devices on a network through multiple hops. It must address scalability issues around representing addresses and routing packets as networks grow large. Routers connect multiple local area networks, which may use different link layer technologies. IP addresses use a hierarchical structure to improve routing scalability. Classless Inter-Domain Routing (CIDR) allows arbitrary allocation of addresses and subnets to minimize routing tables.
1. Asynchronous Transfer Mode (ATM) is a cell-switching and multiplexing technology that combines the benefits of circuit switching and packet switching. It uses fixed-length cells to carry information across networks.
2. ATM networks are built using ATM switches and end-points. Switches are connected via User-Network Interfaces (UNI) and Network-Network Interfaces (NNI). Common ATM end-points include workstations, routers, and video codecs.
3. ATM provides guaranteed bandwidth through virtual circuits established over packet-switched networks. It is highly scalable and efficient for transmitting voice and video due to its small, fixed-length cells.
The document discusses the OSI and TCP/IP models for networking. It describes how each layer of the OSI model adds header data to packets as they move down the stack, and how TCP/IP combines some of these layers. The TCP/IP model layers are application, transport, internet, and network access. It also covers topics like IP addressing, routing, and the data link layer.
This document provides an overview of the Internet Protocol (IP) and describes the layers of the IP stack from lowest to highest: the link layer, internet layer, transport layer, and application layer. It explains key protocols like IP, TCP, UDP, and defines related concepts such as IP addressing, ports, and subnet masking. The document also briefly introduces IPv6 and describes the role of Request for Comments (RFCs) in standardizing Internet technologies.
TCP/IP is the standard communication protocol on the internet. It is comprised of several layers including application, transport, internet, and link layers. The transport layer includes TCP and UDP which provide connection-oriented and connectionless data transmission respectively. TCP ensures reliable data delivery through features like connections, acknowledgments, and flow control. IPv6 is the latest version of the Internet Protocol which addresses the shortcomings of IPv4 like limited address space. IPv6 features include a larger 128-bit address space, simplified header format, built-in security, and autoconfiguration capabilities.
This document discusses IP forwarding and the delivery of IP datagrams. It covers:
- IP networks are logical entities represented as "clouds" that ignore the underlying data link layers.
- For successful delivery, each data link network must connect to another via a router and network prefixes must correspond to unique data link networks.
- Routers and hosts use routing tables to determine the next hop for outgoing datagrams based on destination address and interface.
- IP forwarding processes incoming datagrams, looking them up in routing tables to determine the outgoing interface. It is enabled on routers and disabled on hosts.
- The longest prefix match is used for routing table lookups to determine the most specific match. Route aggregation reduces routing table
Computer Networks and Vulnerabilities
Dr. Wei Chen discusses computer network vulnerabilities in three main areas: the network layer, transport layer, and hands-on experiments. The document outlines IP spoofing, routing attacks, and ICMP attacks that can occur in the network layer. It also discusses protection of confidentiality, integrity, and authentication using cryptography in the transport layer. Dr. Chen provides an outline of hands-on experiments to demonstrate IP packets, IP routing, IP spoofing, TCP SYN flooding, and traffic analysis.
Aplication and Transport layer- a practical approachSarah R. Dowlath
This presentation was done for a Networking course. It really shows from a more practical standpoint how the application layer and the transport layer communicates with each other and operates on a whole to get the job done. It gives the reader more insight of how the pieces come together in an IT networking world.
This document discusses the data link layer and media access control. It covers topics such as:
- The functions of the data link layer including framing, addressing, error control, and media access control.
- Common data link layer protocols like HDLC, PPP, Ethernet, and IEEE 802.11.
- Link layer addressing using MAC addresses and protocols like ARP.
- Media access control for networks including wired technologies like Ethernet and wireless technologies like IEEE 802.11.
This document discusses parallel plane waveguides and rectangular waveguides. It defines waveguides as hollow metallic tubes that transmit electromagnetic waves through successive reflections from the inner walls. Waveguides propagate microwaves and offer advantages like easy manufacturing, ability to handle high power, low loss, and lower attenuation compared to coaxial cables. The document discusses different types of waveguides including rectangular, circular, elliptical, single ridged, and double ridged waveguides. It also compares transmission lines and waveguides, and covers various waveguide modes like TE, TM, and TEM. Finally, it focuses on parallel plane waveguides and rectangular waveguides, discussing their cut-off frequencies and supported modes
This document introduces Simulink and the Communications Blockset. It provides an overview of Simulink and how it can be used to model dynamic and embedded systems through interactive graphical modeling and customizable block libraries. It then describes the Communications Blockset and how it contains blocks for modeling various communication system processes. Finally, it outlines the steps to build an example model that simulates encoding, modulation, transmission over a noisy channel, decoding, and error rate calculation of a random binary message signal.
This document discusses the network layer and IP protocol. It begins by explaining the key functions of the network layer, including forwarding, routing, and connection setup in some network architectures. It then explains the differences between virtual circuit and datagram networks, as well as the forwarding and routing processes. The document outlines the chapter and describes the IP datagram format and functions of the IP, ICMP, and routing protocols. It also provides details about router architecture and functions.
The document provides an overview of the network layer chapter from the textbook "Computer Networking: A Top Down Approach". It outlines the key topics covered in the chapter including network layer service models, how routers work, routing algorithms, IP addressing, and routing protocols used in the Internet. The chapter goals are to understand the principles of the network layer and how these concepts are implemented in the Internet.
The document summarizes key aspects of network layer functionality in computer networks. It discusses the differences between virtual circuit and datagram networks, and how they provide different types of connection-oriented and connectionless services. It also describes the basic functions of routers in forwarding packets using destination addresses and routing algorithms to determine optimal paths through the network.
computer organizational architecture lecture 14 william starliin sahil shama
This document discusses the network layer and key concepts such as virtual circuits, datagrams, forwarding, and routing. It describes the differences between virtual circuit and datagram networks, and how routers work by examining packet headers to forward datagrams using routing algorithms and forwarding tables. The goals of the network layer are to transport segments between hosts using network layer protocols in hosts and routers.
The document provides information on the TCP/IP protocol suite including:
- TCP/IP has 4 layers (Application, Transport, Network, Data Link) compared to OSI's 7 layers.
- Common application layer protocols include FTP, Telnet, SMTP, HTTP.
- Transport layer protocols are TCP and UDP which provide reliable and unreliable data transmission.
- Network layer protocols like IP, ARP, and ICMP handle routing and addressing.
- Layers communicate through encapsulation where each layer adds its own header to protocol data units.
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 summarizes key concepts about the network layer:
1) The network layer is responsible for transporting data segments from sending to receiving hosts by encapsulating segments into datagrams. Routers examine header fields to forward datagrams.
2) The network layer provides three key functions - forwarding, routing, and call setup. Forwarding moves packets through routers, routing determines the path between source and destination, and call setup establishes connections before data flows.
3) The Internet's network layer uses IP to define addressing and datagram format. Routing protocols determine paths and ICMP reports errors. This allows connectionless and best-effort delivery across media.
The document discusses computer networks and network protocols. It begins with an introduction to network protocols and the Internet protocols. It then provides definitions and explanations of communication protocols, including addressing, transmission modes, and error detection/recovery techniques. It lists and describes common network protocols like TCP/IP, routing protocols, FTP, SMTP, and more. It also discusses the OSI model layers, TCP/IP protocol suite, data encapsulation, protocol data units, protocol assignments to layers, and addresses at each layer.
The network layer is responsible for transporting data segments from the sending host to the receiving host. Key functions of the network layer include forwarding, which moves packets through routers, and routing, which determines the path between source and destination. There are two main network architectures: connection-oriented networks using virtual circuits and connectionless networks using datagrams. Routers examine packet headers to perform forwarding and contain input/output ports connected by a switching fabric, as well as a routing processor that maintains routing tables.
09 Systems Software Programming-Network Programming.pptxKushalSrivastava23
This document discusses client-server networking and the TCP/IP protocol stack.
It begins by explaining the client-server model and how servers manage resources for clients. It then describes the layers of a computer network from SAN to WAN. The document discusses how Ethernet segments, bridges, and routers connect local area networks. It introduces the concepts of internet protocols and how they provide naming and delivery of packets across incompatible networks. The roles of IP, TCP, UDP, and sockets in client-server communication are summarized. Finally, it provides examples of functions like getaddrinfo() and getnameinfo() for host and service name resolution.
The network layer routes packets between devices on a network through multiple hops. It must address scalability issues around representing addresses and routing packets as networks grow large. Routers connect multiple local area networks, which may use different link layer technologies. IP addresses use a hierarchical structure to improve routing scalability. Classless Inter-Domain Routing (CIDR) allows arbitrary allocation of addresses and subnets to minimize routing tables.
1. Asynchronous Transfer Mode (ATM) is a cell-switching and multiplexing technology that combines the benefits of circuit switching and packet switching. It uses fixed-length cells to carry information across networks.
2. ATM networks are built using ATM switches and end-points. Switches are connected via User-Network Interfaces (UNI) and Network-Network Interfaces (NNI). Common ATM end-points include workstations, routers, and video codecs.
3. ATM provides guaranteed bandwidth through virtual circuits established over packet-switched networks. It is highly scalable and efficient for transmitting voice and video due to its small, fixed-length cells.
The document discusses the OSI and TCP/IP models for networking. It describes how each layer of the OSI model adds header data to packets as they move down the stack, and how TCP/IP combines some of these layers. The TCP/IP model layers are application, transport, internet, and network access. It also covers topics like IP addressing, routing, and the data link layer.
This document provides an overview of the Internet Protocol (IP) and describes the layers of the IP stack from lowest to highest: the link layer, internet layer, transport layer, and application layer. It explains key protocols like IP, TCP, UDP, and defines related concepts such as IP addressing, ports, and subnet masking. The document also briefly introduces IPv6 and describes the role of Request for Comments (RFCs) in standardizing Internet technologies.
TCP/IP is the standard communication protocol on the internet. It is comprised of several layers including application, transport, internet, and link layers. The transport layer includes TCP and UDP which provide connection-oriented and connectionless data transmission respectively. TCP ensures reliable data delivery through features like connections, acknowledgments, and flow control. IPv6 is the latest version of the Internet Protocol which addresses the shortcomings of IPv4 like limited address space. IPv6 features include a larger 128-bit address space, simplified header format, built-in security, and autoconfiguration capabilities.
This document discusses IP forwarding and the delivery of IP datagrams. It covers:
- IP networks are logical entities represented as "clouds" that ignore the underlying data link layers.
- For successful delivery, each data link network must connect to another via a router and network prefixes must correspond to unique data link networks.
- Routers and hosts use routing tables to determine the next hop for outgoing datagrams based on destination address and interface.
- IP forwarding processes incoming datagrams, looking them up in routing tables to determine the outgoing interface. It is enabled on routers and disabled on hosts.
- The longest prefix match is used for routing table lookups to determine the most specific match. Route aggregation reduces routing table
Computer Networks and Vulnerabilities
Dr. Wei Chen discusses computer network vulnerabilities in three main areas: the network layer, transport layer, and hands-on experiments. The document outlines IP spoofing, routing attacks, and ICMP attacks that can occur in the network layer. It also discusses protection of confidentiality, integrity, and authentication using cryptography in the transport layer. Dr. Chen provides an outline of hands-on experiments to demonstrate IP packets, IP routing, IP spoofing, TCP SYN flooding, and traffic analysis.
Aplication and Transport layer- a practical approachSarah R. Dowlath
This presentation was done for a Networking course. It really shows from a more practical standpoint how the application layer and the transport layer communicates with each other and operates on a whole to get the job done. It gives the reader more insight of how the pieces come together in an IT networking world.
This document discusses the data link layer and media access control. It covers topics such as:
- The functions of the data link layer including framing, addressing, error control, and media access control.
- Common data link layer protocols like HDLC, PPP, Ethernet, and IEEE 802.11.
- Link layer addressing using MAC addresses and protocols like ARP.
- Media access control for networks including wired technologies like Ethernet and wireless technologies like IEEE 802.11.
This document discusses parallel plane waveguides and rectangular waveguides. It defines waveguides as hollow metallic tubes that transmit electromagnetic waves through successive reflections from the inner walls. Waveguides propagate microwaves and offer advantages like easy manufacturing, ability to handle high power, low loss, and lower attenuation compared to coaxial cables. The document discusses different types of waveguides including rectangular, circular, elliptical, single ridged, and double ridged waveguides. It also compares transmission lines and waveguides, and covers various waveguide modes like TE, TM, and TEM. Finally, it focuses on parallel plane waveguides and rectangular waveguides, discussing their cut-off frequencies and supported modes
This document introduces Simulink and the Communications Blockset. It provides an overview of Simulink and how it can be used to model dynamic and embedded systems through interactive graphical modeling and customizable block libraries. It then describes the Communications Blockset and how it contains blocks for modeling various communication system processes. Finally, it outlines the steps to build an example model that simulates encoding, modulation, transmission over a noisy channel, decoding, and error rate calculation of a random binary message signal.
This document analyzes a compact power divider designed to operate at 940 MHz. It presents the circuit diagram, S-parameter diagram, and block diagram of the power divider. It then evaluates the return losses, which refer to power lost due to reflections, and insertion losses, which refer to power lost as the signal passes through the divider. The analysis demonstrates the importance of evaluating these losses for assessing the power divider's performance and compatibility with advanced RF systems.
This document discusses the different types of ambiguity in language. There are three main types: lexical ambiguity, which occurs within a word that has multiple meanings; syntactic ambiguity, which arises from the structure of sentences allowing for more than one interpretation; and anaphoric ambiguity, where a word refers back to something mentioned earlier but is unclear which one it refers to. Examples are provided for each type to illustrate sentences that have more than one plausible meaning due to ambiguity in word choice, structure, or antecedent references.
This document discusses the square microstrip patch antenna. It describes the basic construction and working of the antenna, which consists of a thin metallic patch placed on a ground plane with dielectric material in between. The patch can be square, circular, or rectangular in shape. The document lists some disadvantages of microstrip antennas, such as low efficiency and gain. It also outlines some advantages, including small size, easy fabrication, and ability to support multiple frequencies. Applications mentioned include use in spacecraft, aircraft, telemedicine, and mobile/satellite communication. The document provides details on simulating a square patch antenna model.
A power generating station converts energy from sources like coal, natural gas, nuclear fuel, or renewable sources like wind or solar into electrical energy. It consists of a prime mover, like a steam or gas turbine, connected to an alternator that generates electricity. Common types of generating stations include steam power stations, hydroelectric stations, gas stations, and nuclear stations. Steam power stations, the most common type, burn coal to create steam that drives a steam turbine connected to a generator.
This document discusses conflict management and interpersonal relationships in organizations. It covers topics such as intergroup behavior, categories of interdependence, causes of conflict in organizations, and forms of organizational conflict. There are three main categories of interdependence: pooled, sequential, and reciprocal. Causes of organizational conflict include managerial expectations, communication disruptions, misunderstandings, lack of accountability, unclear responsibilities, interpersonal relationships, scarcity of resources, and conflicts of interest. Forms of organizational conflict discussed are interorganizational, intergroup, intragroup, interpersonal, and intrapersonal.
Group Behaviour refers to people with similar goals behaving in the same way. Characteristics of groups include having 2 or more persons, a formal social structure, common goals, face-to-face interaction, and interdependence. There are several types of groups such as informal groups, formal groups, task groups, command groups, and interest groups. People join groups for reasons like belonging, feeling superior, survival, identity projection, and self-esteem. Groups go through five stages of development and have properties like norms, cohesiveness, roles, status, and size that influence group behavior.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
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.
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.
TIME DIVISION MULTIPLEXING TECHNIQUE FOR COMMUNICATION SYSTEMHODECEDSIET
Time Division Multiplexing (TDM) is a method of transmitting multiple signals over a single communication channel by dividing the signal into many segments, each having a very short duration of time. These time slots are then allocated to different data streams, allowing multiple signals to share the same transmission medium efficiently. TDM is widely used in telecommunications and data communication systems.
### How TDM Works
1. **Time Slots Allocation**: The core principle of TDM is to assign distinct time slots to each signal. During each time slot, the respective signal is transmitted, and then the process repeats cyclically. For example, if there are four signals to be transmitted, the TDM cycle will divide time into four slots, each assigned to one signal.
2. **Synchronization**: Synchronization is crucial in TDM systems to ensure that the signals are correctly aligned with their respective time slots. Both the transmitter and receiver must be synchronized to avoid any overlap or loss of data. This synchronization is typically maintained by a clock signal that ensures time slots are accurately aligned.
3. **Frame Structure**: TDM data is organized into frames, where each frame consists of a set of time slots. Each frame is repeated at regular intervals, ensuring continuous transmission of data streams. The frame structure helps in managing the data streams and maintaining the synchronization between the transmitter and receiver.
4. **Multiplexer and Demultiplexer**: At the transmitting end, a multiplexer combines multiple input signals into a single composite signal by assigning each signal to a specific time slot. At the receiving end, a demultiplexer separates the composite signal back into individual signals based on their respective time slots.
### Types of TDM
1. **Synchronous TDM**: In synchronous TDM, time slots are pre-assigned to each signal, regardless of whether the signal has data to transmit or not. This can lead to inefficiencies if some time slots remain empty due to the absence of data.
2. **Asynchronous TDM (or Statistical TDM)**: Asynchronous TDM addresses the inefficiencies of synchronous TDM by allocating time slots dynamically based on the presence of data. Time slots are assigned only when there is data to transmit, which optimizes the use of the communication channel.
### Applications of TDM
- **Telecommunications**: TDM is extensively used in telecommunication systems, such as in T1 and E1 lines, where multiple telephone calls are transmitted over a single line by assigning each call to a specific time slot.
- **Digital Audio and Video Broadcasting**: TDM is used in broadcasting systems to transmit multiple audio or video streams over a single channel, ensuring efficient use of bandwidth.
- **Computer Networks**: TDM is used in network protocols and systems to manage the transmission of data from multiple sources over a single network medium.
### Advantages of TDM
- **Efficient Use of Bandwidth**: TDM all
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
Comparative analysis between traditional aquaponics and reconstructed aquapon...bijceesjournal
The aquaponic system of planting is a method that does not require soil usage. It is a method that only needs water, fish, lava rocks (a substitute for soil), and plants. Aquaponic systems are sustainable and environmentally friendly. Its use not only helps to plant in small spaces but also helps reduce artificial chemical use and minimizes excess water use, as aquaponics consumes 90% less water than soil-based gardening. The study applied a descriptive and experimental design to assess and compare conventional and reconstructed aquaponic methods for reproducing tomatoes. The researchers created an observation checklist to determine the significant factors of the study. The study aims to determine the significant difference between traditional aquaponics and reconstructed aquaponics systems propagating tomatoes in terms of height, weight, girth, and number of fruits. The reconstructed aquaponics system’s higher growth yield results in a much more nourished crop than the traditional aquaponics system. It is superior in its number of fruits, height, weight, and girth measurement. Moreover, the reconstructed aquaponics system is proven to eliminate all the hindrances present in the traditional aquaponics system, which are overcrowding of fish, algae growth, pest problems, contaminated water, and dead fish.
1. Computer Networking: A
Top-Down Approach
8th edition
Jim Kurose, Keith Ross
Pearson, 2020
Computer
Communication
Networks
Chapter 4
Network Layer:
Data Plane
2. Network layer: our goals
understand principles
behind network layer
services, focusing on data
plane:
• network layer service models
• forwarding versus routing
• how a router works
• addressing
• generalized forwarding
• Internet architecture
instantiation, implementation
in the Internet
• IP protocol
• NAT, middleboxes
Network Layer: 4-2
3. Network layer: “data plane” roadmap
Network layer: overview
• data plane
• control plane
Generalized Forwarding, SDN
• Match+action
• OpenFlow: match+action in action
Middleboxes
Network Layer: 4-3
What’s inside a router
• input ports, switching, output ports
• buffer management, scheduling
IP: the Internet Protocol
• datagram format
• addressing
• network address translation
• IPv6
4. Network-layer services and protocols
transport segment from sending
to receiving host
• sender: encapsulates segments into
datagrams, passes to link layer
• receiver: delivers segments to
transport layer protocol
network layer protocols in every
Internet device: hosts, routers
routers:
• examines header fields in all IP
datagrams passing through it
• moves datagrams from input ports to
output ports to transfer datagrams
along end-end path
mobile network
enterprise
network
national or global ISP
datacenter
network
application
transport
network
link
physical
application
transport
network
link
physical
network
link
physical
network
link
physical
network
link
physical
network
link
physical network
link
physical
Network Layer: 4-4
5. Two key network-layer functions
network-layer functions:
forwarding: move packets from
a router’s input link to
appropriate router output link
analogy: taking a trip
forwarding: process of getting
through single interchange
forwarding
routing
routing: process of planning trip
from source to destination
routing: determine route taken
by packets from source to
destination
• routing algorithms
Network Layer: 4-5
6. Network layer: data plane, control plane
Data plane:
local, per-router function
determines how datagram
arriving on router input port
is forwarded to router
output port
Control plane
network-wide logic
determines how datagram is
routed among routers along end-
end path from source host to
destination host
1
2
3
0111
values in arriving
packet header
two control-plane approaches:
• traditional routing algorithms:
implemented in routers
• software-defined networking (SDN):
implemented in (remote) servers
Network Layer: 4-6
7. Per-router control plane
Individual routing algorithm components in each and every
router interact in the control plane
Routing
Algorithm
data
plane
control
plane
1
2
0111
values in arriving
packet header
3
Network Layer: 4-7
8. Software-Defined Networking (SDN) control plane
Remote controller computes, installs forwarding tables in routers
data
plane
control
plane
Remote Controller
CA
CA CA CA CA
1
2
0111
3
values in arriving
packet header
Network Layer: 4-8
9. Network service model
example services for
individual datagrams:
guaranteed delivery
guaranteed delivery with
less than 40 msec delay
example services for a flow of
datagrams:
in-order datagram delivery
guaranteed minimum bandwidth
to flow
restrictions on changes in inter-
packet spacing
Q: What service model for “channel” transporting datagrams
from sender to receiver?
Network Layer: 4-9
10. Network-layer service model
Network
Architecture
Internet
ATM
ATM
Internet
Internet
Service
Model
best effort
Constant Bit Rate
Available Bit Rate
Intserv Guaranteed
(RFC 1633)
Diffserv (RFC 2475)
Bandwidth
none
Constant rate
Guaranteed min
yes
possible
Loss
no
yes
no
yes
possibly
Order
no
yes
yes
yes
possibly
Timing
no
yes
no
yes
no
No guarantees on:
i. successful datagram delivery to destination
ii. timing or order of delivery
iii. bandwidth available to end-end flow
Internet “best effort” service model
Quality of Service (QoS) Guarantees ?
Network Layer: 4-10
12. Reflections on best-effort service:
simplicity of mechanism has allowed Internet to be widely deployed
adopted
sufficient provisioning of bandwidth allows performance of real-time
applications (e.g., interactive voice, video) to be “good enough” for
“most of the time”
replicated, application-layer distributed services (datacenters, content
distribution networks) connecting close to clients’ networks, allow
services to be provided from multiple locations
congestion control of “elastic” services helps
It’s hard to argue with success of best-effort service model
Network Layer: 4-12
13. Network layer: “data plane” roadmap
Network layer: overview
• data plane
• control plane
What’s inside a router
• input ports, switching, output ports
• buffer management, scheduling
IP: the Internet Protocol
• datagram format
• addressing
• network address translation
• IPv6
Generalized Forwarding, SDN
• Match+action
• OpenFlow: match+action in action
Middleboxes
Network Layer: 4-13
14. Router architecture overview
high-level view of generic router architecture:
high-speed
switching
fabric
routing
processor
router input ports router output ports
forwarding data plane
(hardware) operates
in nanosecond
timeframe
routing, management
control plane (software)
operates in millisecond
time frame
Network Layer: 4-14
15. Input port functions
switch
fabric
line
termination
physical layer:
bit-level reception
link
layer
protocol
(receive)
link layer:
e.g., Ethernet
(chapter 6)
lookup,
forwarding
queueing
decentralized switching:
using header field values, lookup output port using
forwarding table in input port memory (“match plus action”)
goal: complete input port processing at ‘line speed’
input port queuing: if datagrams arrive faster than forwarding
rate into switch fabric
Network Layer: 4-15
16. Input port functions
line
termination
lookup,
forwarding
queueing
decentralized switching:
using header field values, lookup output port using
forwarding table in input port memory (“match plus action”)
destination-based forwarding: forward based only on
destination IP address (traditional)
generalized forwarding: forward based on any set of header
field values
physical layer:
bit-level reception
switch
fabric
link
layer
protocol
(receive)
link layer:
e.g., Ethernet
(chapter 6)
Network Layer: 4-16
17. Q: but what happens if ranges don’t divide up so nicely?
Destination-based forwarding
3
Network Layer: 4-17
18. Longest prefix matching
when looking for forwarding table entry for given
destination address, use longest address prefix that
matches destination address.
longest prefix match
Destination Address Range
11001000 00010111 00010
11001000 00010111 00011000
11001000 00010111 00011
otherwise
Link interface
0
1
2
3
********
***
********
***
********
11001000 00010111 00011000 10101010
examples:
which interface?
which interface?
11001000 00010111 00010110 10100001
Network Layer: 4-18
19. Longest prefix matching
when looking for forwarding table entry for given
destination address, use longest address prefix that
matches destination address.
longest prefix match
Destination Address Range
11001000 00010111 00010
11001000 00010111 00011000
11001000 00010111 00011
otherwise
Link interface
0
1
2
3
11001000 00010111 00011000 10101010
examples:
which interface?
which interface?
********
***
********
***
********
11001000 00010111 00010110 10100001
match!
Network Layer: 4-19
20. Longest prefix matching
when looking for forwarding table entry for given
destination address, use longest address prefix that
matches destination address.
longest prefix match
Destination Address Range
11001000 00010111 00010
11001000 00010111 00011000
11001000 00010111 00011
otherwise
Link interface
0
1
2
3
11001000 00010111 00011000 10101010
examples:
which interface?
which interface?
********
***
********
***
********
11001000 00010111 00010110 10100001
match!
Network Layer: 4-20
21. Longest prefix matching
when looking for forwarding table entry for given
destination address, use longest address prefix that
matches destination address.
longest prefix match
Destination Address Range
11001000 00010111 00010
11001000 00010111 00011000
11001000 00010111 00011
otherwise
Link interface
0
1
2
3
11001000 00010111 00011000 10101010
examples:
which interface?
which interface?
********
***
********
***
********
11001000 00010111 00010110 10100001
match!
Network Layer: 4-21
22. we’ll see why longest prefix matching is used shortly, when
we study addressing
longest prefix matching: often performed using ternary
content addressable memories (TCAMs)
• content addressable: present address to TCAM: retrieve address in
one clock cycle, regardless of table size
• Cisco Catalyst: ~1M routing table entries in TCAM
Longest prefix matching
Network Layer: 4-22
23. transfer packet from input link to appropriate output link
Switching fabrics
high-speed
switching
fabric
N input ports N output ports
.
.
.
.
.
.
switching rate: rate at which packets can be transfer from
inputs to outputs
• often measured as multiple of input/output line rate
• N inputs: switching rate N times line rate desirable
R
R
R
R
(rate: NR,
ideally)
Network Layer: 4-23
24. Switching fabrics
bus
memory
memory
interconnection
network
three major types of switching fabrics:
transfer packet from input link to appropriate output link
switching rate: rate at which packets can be transfer from
inputs to outputs
• often measured as multiple of input/output line rate
• N inputs: switching rate N times line rate desirable
Network Layer: 4-24
25. first generation routers:
traditional computers with switching under direct control of CPU
packet copied to system’s memory
speed limited by memory bandwidth (2 bus crossings per datagram)
Switching via memory
input
port
(e.g.,
Ethernet)
memory
output
port
(e.g.,
Ethernet)
system bus
Network Layer: 4-25
26. datagram from input port memory to output port memory
via a shared bus
bus contention: switching speed limited by bus bandwidth
32 Gbps bus, Cisco 5600: sufficient speed for access routers
Switching via a bus
Network Layer: 4-26
27. Crossbar, Clos networks, other
interconnection nets initially
developed to connect processors in
multiprocessor
Switching via interconnection network
8x8 multistage switch
built from smaller-sized switches
3x3 crossbar
multistage switch: nxn switch from
multiple stages of smaller switches
exploiting parallelism:
• fragment datagram into fixed length cells on
entry
• switch cells through the fabric, reassemble
datagram at exit
3x3 crossbar
Network Layer: 4-27
29. If switch fabric slower than input ports combined -> queueing may
occur at input queues
• queueing delay and loss due to input buffer overflow!
Input port queuing
output port contention: only one red
datagram can be transferred. lower red
packet is blocked
switch
fabric
one packet time later: green
packet experiences HOL blocking
switch
fabric
Head-of-the-Line (HOL) blocking: queued datagram at front of queue
prevents others in queue from moving forward
Network Layer: 4-29
30. Output port queuing
Buffering required when datagrams
arrive from fabric faster than link
transmission rate. Drop policy: which
datagrams to drop if no free buffers?
Scheduling discipline chooses
among queued datagrams for
transmission
Datagrams can be lost
due to congestion, lack of
buffers
Priority scheduling – who
gets best performance,
network neutrality
This is a really important slide
line
termination
link
layer
protocol
(send)
switch
fabric
(rate: NR)
datagram
buffer
queueing R
Network Layer: 4-30
31. Output port queuing
at t, packets more
from input to output
one packet time later
switch
fabric
switch
fabric
buffering when arrival rate via switch exceeds output line speed
queueing (delay) and loss due to output port buffer overflow!
Network Layer: 4-31
32. RFC 3439 rule of thumb: average buffering equal to “typical” RTT
(say 250 msec) times link capacity C
• e.g., C = 10 Gbps link: 2.5 Gbit buffer
How much buffering?
but too much buffering can increase delays (particularly in home
routers)
• long RTTs: poor performance for realtime apps, sluggish TCP response
• recall delay-based congestion control: “keep bottleneck link just full
enough (busy) but no fuller”
RTT C
.
N
more recent recommendation: with N flows, buffering equal to
Network Layer: 4-32
33. Buffer Management
buffer management:
drop: which packet to add,
drop when buffers are full
• tail drop: drop arriving
packet
• priority: drop/remove on
priority basis
line
termination
link
layer
protocol
(send)
switch
fabric
datagram
buffer
queueing
scheduling
marking: which packets to
mark to signal congestion
(ECN, RED)
R
queue
(waiting area)
packet
arrivals
packet
departures
link
(server)
Abstraction: queue
R
Network Layer: 4-33
34. packet scheduling: deciding
which packet to send next on
link
• first come, first served
• priority
• round robin
• weighted fair queueing
Packet Scheduling: FCFS
FCFS: packets transmitted in
order of arrival to output
port
also known as: First-in-first-
out (FIFO)
real world examples?
queue
(waiting area)
packet
arrivals
packet
departures
link
(server)
Abstraction: queue
R
Network Layer: 4-34
35. Priority scheduling:
arriving traffic classified,
queued by class
• any header fields can be
used for classification
Scheduling policies: priority
high priority queue
low priority queue
arrivals
classify departures
link
1 3 2 4 5
arrivals
departures
packet
in
service
send packet from highest
priority queue that has
buffered packets
• FCFS within priority class
1 3 4
2
5
1 3 2 4 5
Network Layer: 4-35
36. Round Robin (RR) scheduling:
arriving traffic classified,
queued by class
• any header fields can be
used for classification
Scheduling policies: round robin
classify
arrivals
departures
link
R
server cyclically, repeatedly
scans class queues,
sending one complete
packet from each class (if
available) in turn
Network Layer: 4-36
37. Weighted Fair Queuing (WFQ):
generalized Round Robin
Scheduling policies: weighted fair queueing
classify
arrivals
departures
link
R
w1
w2
w3
wi
Sjwj
minimum bandwidth
guarantee (per-traffic-class)
each class, i, has weight, wi,
and gets weighted amount
of service in each cycle:
Network Layer: 4-37
38. Sidebar: Network Neutrality
What is network neutrality?
technical: how an ISP should share/allocation its resources
• packet scheduling, buffer management are the mechanisms
social, economic principles
• protecting free speech
• encouraging innovation, competition
enforced legal rules and policies
Different countries have different “takes” on network neutrality
Network Layer: 4-38
39. Sidebar: Network Neutrality
2015 US FCC Order on Protecting and Promoting an Open Internet: three
“clear, bright line” rules:
no blocking … “shall not block lawful content, applications, services,
or non-harmful devices, subject to reasonable network management.”
no throttling … “shall not impair or degrade lawful Internet traffic
on the basis of Internet content, application, or service, or use of a
non-harmful device, subject to reasonable network management.”
no paid prioritization. … “shall not engage in paid prioritization”
Network Layer: 4-39
40. ISP: telecommunications or information service?
US Telecommunication Act of 1934 and 1996:
• Title II: imposes “common carrier duties” on telecommunications
services: reasonable rates, non-discrimination and requires regulation
• Title I: applies to information services:
• no common carrier duties (not regulated)
• but grants FCC authority “… as may be necessary in the execution
of its functions”4
Is an ISP a “telecommunications service” or an “information
service” provider?
the answer really matters from a regulatory standpoint!
Network Layer: 4-40
41. Network layer: “data plane” roadmap
Network layer: overview
• data plane
• control plane
What’s inside a router
• input ports, switching, output ports
• buffer management, scheduling
IP: the Internet Protocol
• datagram format
• addressing
• network address translation
• IPv6
Generalized Forwarding, SDN
• match+action
• OpenFlow: match+action in action
Middleboxes
Network Layer: 4-41
42. Network Layer: Internet
host, router network layer functions:
IP protocol
• datagram format
• addressing
• packet handling conventions
ICMP protocol
• error reporting
• router “signaling”
transport layer: TCP, UDP
link layer
physical layer
network
layer
forwarding
table
Path-selection
algorithms:
implemented in
• routing protocols
(OSPF, BGP)
• SDN controller
Network Layer: 4-42
43. IP Datagram format
ver length
32 bits
payload data
(variable length,
typically a TCP
or UDP segment)
16-bit identifier
header
checksum
time to
live
source IP address
head.
len
type of
service
flgs
fragment
offset
upper
layer
destination IP address
options (if any)
IP protocol version number
header length(bytes)
upper layer protocol (e.g., TCP or UDP)
total datagram
length (bytes)
“type” of service:
diffserv (0:5)
ECN (6:7)
fragmentation/
reassembly
TTL: remaining max hops
(decremented at each router)
20 bytes of TCP
20 bytes of IP
= 40 bytes + app
layer overhead for
TCP+IP
overhead
e.g., timestamp, record
route taken
32-bit source IP address
32-bit destination IP address
header checksum
Maximum length: 64K bytes
Typically: 1500 bytes or less
Network Layer: 4-43
44. IP address: 32-bit identifier
associated with each host or
router interface
interface: connection between
host/router and physical link
• router’s typically have multiple
interfaces
• host typically has one or two
interfaces (e.g., wired Ethernet,
wireless 802.11)
IP addressing: introduction
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
223.1.1.1 = 11011111 00000001 00000001 00000001
223 1 1
1
dotted-decimal IP address notation:
Network Layer: 4-44
45. IP address: 32-bit identifier
associated with each host or
router interface
interface: connection between
host/router and physical link
• router’s typically have multiple
interfaces
• host typically has one or two
interfaces (e.g., wired Ethernet,
wireless 802.11)
IP addressing: introduction
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
223.1.1.1 = 11011111 00000001 00000001 00000001
223 1 1
1
dotted-decimal IP address notation:
Network Layer: 4-45
46. IP addressing: introduction
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
Q: how are interfaces
actually connected?
A: wired
Ethernet interfaces
connected by
Ethernet switches
A: wireless WiFi interfaces
connected by WiFi base station
For now: don’t need to worry
about how one interface is
connected to another (with no
intervening router)
A: we’ll learn about
that in chapters 6, 7
Network Layer: 4-46
49. Subnets
where are the
subnets?
what are the
/24 subnet
addresses?
223.1.1.1
223.1.1.3
223.1.1.4
223.1.2.2
223.1.2.6
223.1.3.2
223.1.3.1
223.1.3.27
223.1.1.2
223.1.7.0
223.1.7.1
223.1.8.0
223.1.8.1
223.1.9.1
223.1.9.2
223.1.2.1
subnet 223.1.1/24
subnet 223.1.7/24
subnet 223.1.3/24
subnet 223.1.2/24
subnet 223.1.9/24
subnet 223.1.8/24
Network Layer: 4-49
50. IP addressing: CIDR
CIDR: Classless InterDomain Routing (pronounced “cider”)
• subnet portion of address of arbitrary length
• address format: a.b.c.d/x, where x is # bits in subnet portion
of address
11001000 00010111 00010000 00000000
subnet
part
host
part
200.23.16.0/23
Network Layer: 4-50
51. IP addresses: how to get one?
That’s actually two questions:
1.Q: How does a host get IP address within its network (host part of
address)?
2.Q: How does a network get IP address for itself (network part of
address)
How does host get IP address?
hard-coded by sysadmin in config file (e.g., /etc/rc.config in UNIX)
DHCP: Dynamic Host Configuration Protocol: dynamically get address
from as server
• “plug-and-play”
Network Layer: 4-51
52. DHCP: Dynamic Host Configuration Protocol
goal: host dynamically obtains IP address from network server when it
“joins” network
can renew its lease on address in use
allows reuse of addresses (only hold address while
connected/on)
support for mobile users who join/leave network
DHCP overview:
host broadcasts DHCP discover msg [optional]
DHCP server responds with DHCP offer msg [optional]
host requests IP address: DHCP request msg
DHCP server sends address: DHCP ack msg
Network Layer: 4-52
53. DHCP client-server scenario
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2
223.1.3.1
223.1.3.27
DHCP server
223.1.2.5
arriving DHCP client needs
address in this network
Typically, DHCP server will be co-
located in router, serving all subnets
to which router is attached
Network Layer: 4-53
54. DHCP client-server scenario
DHCP server: 223.1.2.5
Arriving client
DHCP discover
src : 0.0.0.0, 68
dest.: 255.255.255.255,67
yiaddr: 0.0.0.0
transaction ID: 654
DHCP offer
src: 223.1.2.5, 67
dest: 255.255.255.255, 68
yiaddrr: 223.1.2.4
transaction ID: 654
lifetime: 3600 secs
DHCP request
src: 0.0.0.0, 68
dest:: 255.255.255.255, 67
yiaddrr: 223.1.2.4
transaction ID: 655
lifetime: 3600 secs
DHCP ACK
src: 223.1.2.5, 67
dest: 255.255.255.255, 68
yiaddrr: 223.1.2.4
transaction ID: 655
lifetime: 3600 secs
Broadcast: is there a
DHCP server out there?
Broadcast: I’m a DHCP
server! Here’s an IP
address you can use
Broadcast: OK. I would
like to use this IP address!
Broadcast: OK. You’ve
got that IP address!
The two steps above can
be skipped “if a client
remembers and wishes to
reuse a previously
allocated network address”
[RFC 2131]
Network Layer: 4-54
55. DHCP: more than IP addresses
DHCP can return more than just allocated IP address on
subnet:
address of first-hop router for client
name and IP address of DNS sever
network mask (indicating network versus host portion of address)
Network Layer: 4-55
56. DHCP: example
Connecting laptop will use DHCP
to get IP address, address of first-
hop router, address of DNS server.
router with DHCP
server built into
router
DHCP REQUEST message encapsulated
in UDP, encapsulated in IP, encapsulated
in Ethernet
Ethernet frame broadcast (dest:
FFFFFFFFFFFF) on LAN, received at router
running DHCP server
Ethernet demux’ed to IP demux’ed,
UDP demux’ed to DHCP
168.1.1.1
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
DHCP
Network Layer: 4-56
57. DHCP: example
DCP server formulates DHCP ACK
containing client’s IP address, IP
address of first-hop router for client,
name & IP address of DNS server
encapsulated DHCP server reply
forwarded to client, demuxing up to
DHCP at client
router with DHCP
server built into
router
DHCP
DHCP
DHCP
DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
UDP
IP
Eth
Phy
DHCP
DHCP
DHCP
DHCP
client now knows its IP address, name
and IP address of DNS server, IP
address of its first-hop router
Network Layer: 4-57
58. IP addresses: how to get one?
Q: how does network get subnet part of IP address?
A: gets allocated portion of its provider ISP’s address space
ISP's block 11001000 00010111 00010000 00000000 200.23.16.0/20
ISP can then allocate out its address space in 8 blocks:
Organization 0 11001000 00010111 00010000 00000000 200.23.16.0/23
Organization 1 11001000 00010111 00010010 00000000 200.23.18.0/23
Organization 2 11001000 00010111 00010100 00000000 200.23.20.0/23
... ….. …. ….
Organization 7 11001000 00010111 00011110 00000000 200.23.30.0/23
Network Layer: 4-58
59. Hierarchical addressing: route aggregation
“Send me anything
with addresses
beginning
200.23.16.0/20”
200.23.16.0/23
200.23.18.0/23
200.23.30.0/23
Fly-By-Night-ISP
Organization 0
Organization 7
Internet
Organization 1
ISPs-R-Us
“Send me anything
with addresses
beginning
199.31.0.0/16”
200.23.20.0/23
Organization 2
.
.
.
.
.
.
hierarchical addressing allows efficient advertisement of
routing information:
Network Layer: 4-59
60. Hierarchical addressing: more specific routes
“Send me anything
with addresses
beginning
200.23.16.0/20”
200.23.16.0/23
200.23.30.0/23
Fly-By-Night-ISP
Organization 0
Organization 7
Internet
200.23.18.0/23
Organization 1
ISPs-R-Us
“Send me anything
with addresses
beginning
199.31.0.0/16”
200.23.20.0/23
Organization 2
.
.
.
.
.
.
Organization 1 moves from Fly-By-Night-ISP to ISPs-R-Us
ISPs-R-Us now advertises a more specific route to Organization 1
200.23.18.0/23
Organization 1
“or 200.23.18.0/23”
Network Layer: 4-60
61. Hierarchical addressing: more specific routes
“Send me anything
with addresses
beginning
200.23.16.0/20”
200.23.16.0/23
200.23.30.0/23
Fly-By-Night-ISP
Organization 0
Organization 7
Internet
ISPs-R-Us
“Send me anything
with addresses
beginning
199.31.0.0/16”
200.23.20.0/23
Organization 2
.
.
.
.
.
.
Organization 1 moves from Fly-By-Night-ISP to ISPs-R-Us
ISPs-R-Us now advertises a more specific route to Organization 1
200.23.18.0/23
Organization 1
“or 200.23.18.0/23”
Network Layer: 4-61
62. IP addressing: last words ...
Q: how does an ISP get block of
addresses?
A: ICANN: Internet Corporation for
Assigned Names and Numbers
http://www.icann.org/
• allocates IP addresses, through 5
regional registries (RRs) (who may
then allocate to local registries)
• manages DNS root zone, including
delegation of individual TLD (.com,
.edu , …) management
Q: are there enough 32-bit IP
addresses?
ICANN allocated last chunk of
IPv4 addresses to RRs in 2011
NAT (next) helps IPv4 address
space exhaustion
IPv6 has 128-bit address space
"Who the hell knew how much address
space we needed?" Vint Cerf (reflecting
on decision to make IPv4 address 32 bits
long)
Network Layer: 4-62
63. Network layer: “data plane” roadmap
Network layer: overview
• data plane
• control plane
What’s inside a router
• input ports, switching, output ports
• buffer management, scheduling
IP: the Internet Protocol
• datagram format
• addressing
• network address translation
• IPv6
Generalized Forwarding, SDN
• match+action
• OpenFlow: match+action in action
Middleboxes
Network Layer: 4-63
64. 10.0.0.1
10.0.0.2
10.0.0.3
10.0.0.4
local network (e.g., home
network) 10.0.0/24
138.76.29.7
rest of
Internet
NAT: network address translation
datagrams with source or destination in
this network have 10.0.0/24 address for
source, destination (as usual)
all datagrams leaving local network have
same source NAT IP address: 138.76.29.7,
but different source port numbers
NAT: all devices in local network share just one IPv4 address as
far as outside world is concerned
Network Layer: 4-64
65. all devices in local network have 32-bit addresses in a “private” IP
address space (10/8, 172.16/12, 192.168/16 prefixes) that can only
be used in local network
advantages:
just one IP address needed from provider ISP for all devices
can change addresses of host in local network without notifying
outside world
can change ISP without changing addresses of devices in local
network
security: devices inside local net not directly addressable, visible
by outside world
NAT: network address translation
Network Layer: 4-65
66. implementation: NAT router must (transparently):
outgoing datagrams: replace (source IP address, port #) of every
outgoing datagram to (NAT IP address, new port #)
• remote clients/servers will respond using (NAT IP address, new port
#) as destination address
remember (in NAT translation table) every (source IP address, port #)
to (NAT IP address, new port #) translation pair
incoming datagrams: replace (NAT IP address, new port #) in
destination fields of every incoming datagram with corresponding
(source IP address, port #) stored in NAT table
NAT: network address translation
Network Layer: 4-66
68. NAT has been controversial:
• routers “should” only process up to layer 3
• address “shortage” should be solved by IPv6
• violates end-to-end argument (port # manipulation by network-layer device)
• NAT traversal: what if client wants to connect to server behind NAT?
but NAT is here to stay:
• extensively used in home and institutional nets, 4G/5G cellular nets
NAT: network address translation
Network Layer: 4-68
69. initial motivation: 32-bit IPv4 address space would be
completely allocated
additional motivation:
• speed processing/forwarding: 40-byte fixed length header
• enable different network-layer treatment of “flows”
IPv6: motivation
Network Layer: 4-69
70. IPv6 datagram format
payload (data)
destination address
(128 bits)
source address
(128 bits)
payload len next hdr hop limit
flow label
pri
ver
32 bits
priority: identify
priority among
datagrams in flow
flow label: identify
datagrams in same
"flow.” (concept of
“flow” not well defined).
128-bit
IPv6 addresses
What’s missing (compared with IPv4):
no checksum (to speed processing at routers)
no fragmentation/reassembly
no options (available as upper-layer, next-header protocol at router)
Network Layer: 4-70
71. not all routers can be upgraded simultaneously
• no “flag days”
• how will network operate with mixed IPv4 and IPv6 routers?
Transition from IPv4 to IPv6
IPv4 source, dest addr
IPv4 header fields
IPv4 datagram
IPv6 datagram
IPv4 payload
UDP/TCP payload
IPv6 source dest addr
IPv6 header fields
tunneling: IPv6 datagram carried as payload in IPv4 datagram among
IPv4 routers (“packet within a packet”)
• tunneling used extensively in other contexts (4G/5G)
Network Layer: 4-71
72. Tunneling and encapsulation
Ethernet connecting
two IPv6 routers:
Ethernet connects two
IPv6 routers
A B
IPv6 IPv6
E F
IPv6 IPv6
Link-layer frame
IPv6 datagram
The usual: datagram as payload in link-layer frame
A B
IPv6 IPv6/v4
E F
IPv6/v4 IPv6
IPv4 network
IPv4 network
connecting two
IPv6 routers
Network Layer: 4-72
73. Tunneling and encapsulation
Ethernet connecting
two IPv6 routers:
Ethernet connects two
IPv6 routers
A B
IPv6 IPv6
E F
IPv6 IPv6
IPv4 tunnel
connecting two
IPv6 routers
IPv4 tunnel
connecting IPv6 routers
A B
IPv6
E F
IPv6
Link-layer frame
IPv6 datagram
The usual: datagram as payload in link-layer frame
IPv4 datagram
IPv6 datagram
tunneling: IPv6 datagram as payload in a IPv4 datagram
IPv6/v4 IPv6/v4
Network Layer: 4-73
74. B-to-C:
IPv6 inside
IPv4
Flow: X
Src: A
Dest: F
data
src:B
dest: E
Tunneling
physical view:
IPv4 IPv4
E
IPv6/v4 IPv6
F
C D
A B
IPv6 IPv6/v4
logical view:
IPv4 tunnel
connecting IPv6 routers
A B
IPv6 IPv6/v4
E F
IPv6/v4 IPv6
flow: X
src: A
dest: F
data
A-to-B:
IPv6
Flow: X
Src: A
Dest: F
data
src:B
dest: E
B-to-C:
IPv6 inside
IPv4
E-to-F:
IPv6
flow: X
src: A
dest: F
data
B-to-C:
IPv6 inside
IPv4
Flow: X
Src: A
Dest: F
data
src:B
dest: E
Note source and
destination
addresses!
Network Layer: 4-74
75. Google1: ~ 30% of clients access services via IPv6
NIST: 1/3 of all US government domains are IPv6 capable
IPv6: adoption
1
https://www.google.com/intl
/en/ipv6/statistics.html
Network Layer: 4-75
76. Google1: ~ 30% of clients access services via IPv6
NIST: 1/3 of all US government domains are IPv6 capable
Long (long!) time for deployment, use
• 25 years and counting!
• think of application-level changes in last 25 years: WWW, social
media, streaming media, gaming, telepresence, …
• Why?
IPv6: adoption
1 https://www.google.com/intl/en/ipv6/statistics.html
Network Layer: 4-76
77. Network layer: “data plane” roadmap
Network layer: overview
• data plane
• control plane
Generalized Forwarding, SDN
• Match+action
• OpenFlow: match+action in action
Middleboxes
Network Layer: 4-77
What’s inside a router
• input ports, switching, output ports
• buffer management, scheduling
IP: the Internet Protocol
• datagram format
• addressing
• network address translation
• IPv6
78. 1
2
0111
3
values in arriving
packet header
Generalized forwarding: match plus action
Review: each router contains a forwarding table
“match plus action” abstraction: match bits in arriving packet, take action
• generalized forwarding:
• many header fields can determine action
• many action possible: drop/copy/modify/log packet
forwarding table
(aka: flow table)
(aka: flow table)
• destination-based forwarding: forward based on dest. IP address
Network Layer: 4-78
79. flow: defined by header field values (in link-, network-, transport-layer fields)
generalized forwarding: simple packet-handling rules
• match: pattern values in packet header fields
• actions: for matched packet: drop, forward, modify, matched packet or send
matched packet to controller
• priority: disambiguate overlapping patterns
• counters: #bytes and #packets
Flow table abstraction
Router’s flow table define
router’s match+action rules
Flow table
match action
Network Layer: 4-79
80. flow: defined by header fields
generalized forwarding: simple packet-handling rules
• match: pattern values in packet header fields
• actions: for matched packet: drop, forward, modify, matched packet or send
matched packet to controller
• priority: disambiguate overlapping patterns
• counters: #bytes and #packets
Flow table
match action
1
2
3
4
* : wildcard
src=10.1.2.3, dest=*.*.*.* send to controller
src=1.2.*.*, dest=*.*.*.* drop
src = *.*.*.*, dest=3.4.*.* forward(2)
Flow table abstraction
Network Layer: 4-80
81. OpenFlow: flow table entries
Match Action Stats
1. Forward packet to port(s)
2. Drop packet
3. Modify fields in header(s)
4. Encapsulate and forward to controller
Packet + byte counters
Header fields to match:
Ingress
Port
Src
MAC
Dst
MAC
Eth
Type
VLAN
ID
IP
ToS
IP
Proto
IP Src IP Dst
TCP/UDP
Src Port
VLAN
Pri
TCP/UDP
Dst Port
Link layer Network layer Transport layer
Network Layer: 4-81
82. OpenFlow: examples
IP datagrams destined to IP address 51.6.0.8 should be forwarded to router output port 6
Block (do not forward) all datagrams destined to TCP port 22 (ssh port #)
Block (do not forward) all datagrams sent by host 128.119.1.1
Destination-based forwarding:
* * * * * * 51.6.0.8 * * * port6
Switch
Port
MAC
src
MAC
dst
Eth
type
VLAN
ID
IP
Src
IP
Dst
IP
Prot
TCP
s-port
TCP
d-port Action
VLAN
Pri
IP
ToS
*
*
* * * * * * * * * *
Firewall:
drop
Switch
Port
MAC
src
MAC
dst
Eth
type
VLAN
ID
IP
Src
IP
Dst
IP
Prot
TCP
s-port
TCP
d-port Action
VLAN
Pri
IP
ToS
22
*
Switch
Port
MAC
src
MAC
dst
Eth
type
VLAN
ID
IP
Src
IP
Dst
IP
Prot
TCP
s-port
TCP
d-port Action
VLAN
Pri
IP
ToS
* * * * * * * * * * drop
*
128.119.1.1
Network Layer: 4-82
83. OpenFlow: examples
Layer 2 destination-based forwarding:
layer 2 frames with destination MAC address 22:A7:23:11:E1:02 should be forwarded to
output port 3
* * * * * * * * * port3
22:A7:23:
11:E1:02 * *
Switch
Port
MAC
src
MAC
dst
Eth
type
VLAN
ID
IP
Src
IP
Dst
IP
Prot
TCP
s-port
TCP
d-port Action
VLAN
Pri
IP
ToS
Network Layer: 4-83
84. match+action: abstraction unifies different kinds of devices
OpenFlow abstraction
Router
• match: longest
destination IP prefix
• action: forward out a
link
Switch
• match: destination MAC
address
• action: forward or flood
Firewall
• match: IP addresses and
TCP/UDP port numbers
• action: permit or deny
NAT
• match: IP address and port
• action: rewrite address and
port
Network Layer: 4-84
85. OpenFlow example
Host h1
10.1.0.1
Host h2
10.1.0.2
Host h4
10.2.0.4
Host h3
10.2.0.3
Host h5
10.3.0.5
s1 s2
s3
1
2
3
4
1
2
3
4
1
2
3
4
Host h6
10.3.0.6
controller
Orchestrated tables can create
network-wide behavior, e.g.,:
datagrams from hosts h5 and
h6 should be sent to h3 or h4,
via s1 and from there to s2
Network Layer: 4-85
86. OpenFlow example
IP Src = 10.3.*.*
IP Dst = 10.2.*.*
forward(3)
match action
ingress port = 2
IP Dst = 10.2.0.3
ingress port = 2
IP Dst = 10.2.0.4
forward(3)
match action
forward(4)
ingress port = 1
IP Src = 10.3.*.*
IP Dst = 10.2.*.*
forward(4)
match action
Host h1
10.1.0.1
Host h2
10.1.0.2
Host h4
10.2.0.4
Host h3
10.2.0.3
Host h5
10.3.0.5
s1 s2
s3
1
2
3
4
1
2
3
4
1
2
3
4
Host h6
10.3.0.6
controller
Orchestrated tables can create
network-wide behavior, e.g.,:
datagrams from hosts h5 and
h6 should be sent to h3 or h4,
via s1 and from there to s2
Network Layer: 4-86
87. Generalized forwarding: summary
“match plus action” abstraction: match bits in arriving packet header(s) in
any layers, take action
• matching over many fields (link-, network-, transport-layer)
• local actions: drop, forward, modify, or send matched packet to
controller
• “program” network-wide behaviors
simple form of “network programmability”
• programmable, per-packet “processing”
• historical roots: active networking
• today: more generalized programming:
P4 (see p4.org).
Network Layer: 4-87
88. Network layer: “data plane” roadmap
Network Layer: 4-88
Network layer: overview
What’s inside a router
IP: the Internet Protocol
Generalized Forwarding
Middleboxes
• middlebox functions
• evolution, architectural principles of
the Internet
89. Middleboxes
“any intermediary box performing functions apart
from normal, standard functions of an IP router on
the data path between a source host and
destination host”
Middlebox (RFC 3234)
90. Middleboxes everywhere!
enterprise
network
national or global ISP
datacenter
network
NAT: home,
cellular,
institutional
Firewalls, IDS: corporate,
institutional, service providers,
ISPs
Load balancers:
corporate, service
provider, data center,
mobile nets
Caches: service
provider, mobile, CDNs
Application-
specific: service
providers,
institutional,
CDN
91. Middleboxes
initially: proprietary (closed) hardware solutions
move towards “whitebox” hardware implementing open API
move away from proprietary hardware solutions
programmable local actions via match+action
move towards innovation/differentiation in software
SDN: (logically) centralized control and configuration management
often in private/public cloud
network functions virtualization (NFV): programmable services over
white box networking, computation, storage
92. The IP hourglass
IP
TCP UDP
HTTP SMTP
QUIC DASH
RTP …
Ethernet
WiFi Bluetooth
PPP
PDCP
…
copper radio fiber
Internet’s “thin waist”:
one network layer
protocol: IP
must be implemented
by every (billions) of
Internet-connected
devices
many protocols
in physical, link,
transport, and
application
layers
93. The IP hourglass, at middle age
IP
TCP UDP
HTTP SMTP
QUIC DASH
RTP …
Ethernet
WiFi Bluetooth
PPP
PDCP
…
copper radio fiber
Internet’s middle age
“love handles”?
middleboxes,
operating inside the
network
Firewalls
caching
94. Architectural Principles of the Internet
“Many members of the Internet community would argue that there is no architecture, but only a tradition,
which was not written down for the first 25 years (or at least not by the IAB). However, in very general terms,
the community believes that
RFC 1958
the goal is connectivity, the tool is the Internet
Protocol, and the intelligence is end to end rather than hidden in the
network.”
Three cornerstone beliefs:
simple connectivity
IP protocol: that narrow waist
intelligence, complexity at network edge
95. The end-end argument
some network functionality (e.g., reliable data transfer, congestion)
can be implemented in network, or at network edge
end-end implementation of reliable data transfer
application
transport
network
data link
physical
application
transport
network
data link
physical
application
transport
network
data link
physical
application
transport
network
data link
physical
network
link
physical
network
link
physical
network
link
physical
network
link
physical
network
link
physical
network
link
physical
hop-by-hop (in-network) implementation of reliable data transfer
96. The end-end argument
“The function in question can completely and correctly be implemented only
with the knowledge and help of the application standing at the end points of the
communication system. Therefore, providing that questioned function as a
feature of the communication system itself is not possible. (Sometimes an
incomplete version of the function provided by the communication system may
be useful as a performance enhancement.)
We call this line of reasoning against low-level function implementation the “end-
to-end argument.”
Saltzer, Reed, Clark 1981
some network functionality (e.g., reliable data transfer, congestion)
can be implemented in network, or at network edge
97. Where’s the intelligence?
20th century phone net:
• intelligence/computing at
network switches
Internet (pre-2005)
• intelligence, computing at
edge
Internet (post-2005)
• programmable network devices
• intelligence, computing, massive
application-level infrastructure at edge
98. Question: how are forwarding tables (destination-based forwarding)
or flow tables (generalized forwarding) computed?
Answer: by the control plane (next chapter)
Chapter 4: done!
Generalized Forwarding, SDN
Middleboxes
Network layer: overview
What’s inside a router
IP: the Internet Protocol
100. network links have MTU (max.
transfer size) - largest possible
link-level frame
• different link types, different MTUs
large IP datagram divided
(“fragmented”) within net
• one datagram becomes several
datagrams
• “reassembled” only at destination
• IP header bits used to identify, order
related fragments
IP fragmentation/reassembly
Network Layer: 4-100
fragmentation:
in: one large datagram
out: 3 smaller datagrams
reassembly
…
…
101. IP fragmentation/reassembly
Network Layer: 4-101
ID
=x
offset
=0
fragflag
=0
length
=4000
ID
=x
offset
=0
fragflag
=1
length
=1500
ID
=x
offset
=185
fragflag
=1
length
=1500
ID
=x
offset
=370
fragflag
=0
length
=1040
one large datagram becomes
several smaller datagrams
example:
4000 byte datagram
MTU = 1500 bytes
1480 bytes in
data field
offset =
1480/8
102. DHCP: Wireshark output (home LAN)
Network Layer: 4-102
Message type: Boot Reply (2)
Hardware type: Ethernet
Hardware address length: 6
Hops: 0
Transaction ID: 0x6b3a11b7
Seconds elapsed: 0
Bootp flags: 0x0000 (Unicast)
Client IP address: 192.168.1.101 (192.168.1.101)
Your (client) IP address: 0.0.0.0 (0.0.0.0)
Next server IP address: 192.168.1.1 (192.168.1.1)
Relay agent IP address: 0.0.0.0 (0.0.0.0)
Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a)
Server host name not given
Boot file name not given
Magic cookie: (OK)
Option: (t=53,l=1) DHCP Message Type = DHCP ACK
Option: (t=54,l=4) Server Identifier = 192.168.1.1
Option: (t=1,l=4) Subnet Mask = 255.255.255.0
Option: (t=3,l=4) Router = 192.168.1.1
Option: (6) Domain Name Server
Length: 12; Value: 445747E2445749F244574092;
IP Address: 68.87.71.226;
IP Address: 68.87.73.242;
IP Address: 68.87.64.146
Option: (t=15,l=20) Domain Name = "hsd1.ma.comcast.net."
Message type: Boot Request (1)
Hardware type: Ethernet
Hardware address length: 6
Hops: 0
Transaction ID: 0x6b3a11b7
Seconds elapsed: 0
Bootp flags: 0x0000 (Unicast)
Client IP address: 0.0.0.0 (0.0.0.0)
Your (client) IP address: 0.0.0.0 (0.0.0.0)
Next server IP address: 0.0.0.0 (0.0.0.0)
Relay agent IP address: 0.0.0.0 (0.0.0.0)
Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a)
Server host name not given
Boot file name not given
Magic cookie: (OK)
Option: (t=53,l=1) DHCP Message Type = DHCP Request
Option: (61) Client identifier
Length: 7; Value: 010016D323688A;
Hardware type: Ethernet
Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a)
Option: (t=50,l=4) Requested IP Address = 192.168.1.101
Option: (t=12,l=5) Host Name = "nomad"
Option: (55) Parameter Request List
Length: 11; Value: 010F03062C2E2F1F21F92B
1 = Subnet Mask; 15 = Domain Name
3 = Router; 6 = Domain Name Server
44 = NetBIOS over TCP/IP Name Server
……
reply
request
Editor's Notes
Text for this animation:
This all works out pretty nice and looks pretty simple!
But of course the devil is in the details, as the saying goes.
What happens, for example, when a subset of addresses say in this first range should go to say interface 3, rather than interface 0. Well, of course we could split the first address range into multiple pieces, and add in this new subrange with its new destination output port. But it turns out there’s a much simpler and elegant way to do this. Known as longest prefix matching.
You might think that more buffering is a good thing. Buffering is a bit like salt—just the right amount of salt makes food better, but too much makes it inedible!
The 20th century phone network had dumb network endpoints, really by definition. The end points were rotary phones that maybe only your parents and grandparents remember; they weren’t computers. They really were dumb devices, and therefore the phone network had programmable switches that were quite smart. All functionality – well, all of the intelligence - was implemented within the network. It HAD to be. The end systems could not do anything more than send digits and send audio signals.
When the Internet came along, the endpoints and the switches were both programmable computers. So where to put the complexity? RFC 1958 – the architectural principles of the Internet RFC - that says “intelligence is end to end rather than hidden in the network.” That puts the intelligence clearly at the edge, like we see here. And that’s possible because the edge devices are smart; they’re programmable. Well that’s the diagram as I remember it 20 years ago.
And in the 20 years since, as we see the rise of middleboxes and SDN, we’re now seeing intelligence (in software) layered on top of “dumb” whiteboxes within the network. So I might add a brain here today. And with datacenters and content distribution networks, we see even smarter and more sophisticated application-level infrastructure being connected at points within the network. So now there are clearly much much bigger, much more computationally intensive and complex, endpoints if you will in today’s Internet