chapter- 6 network layer of computer network
- 1. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The Network Layer Chapter 6
- 2. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The network layer is concerned with getting packets from the source all the way to the destination. Getting to the destination may require making many hops at intermediate routers along the way. The network layer is the lowest layer that deals with end- to-end transmission. To achieve its goals, the network layer must know about the topology of the network (i.e., the set of all routers and links) and choose appropriate paths through it, even for large networks. It must also take care when choosing routes to avoid overloading some of the communication lines and routers while leaving others idle.
- 3. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Propagation Internet Protocol
- 4. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Network Layer Design Issues • Store-and-forward packet switching • Services provided to transport layer • Implementation of connectionless service • Implementation of connection-oriented service • Comparison of virtual-circuit and datagram networks
- 5. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Store-and-Forward Packet Switching The environment of the network layer protocols. ISP’s equipment
- 6. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Services Provided to the Transport Layer 1. Services independent of router technology. 2. Transport layer shielded from number, type, topology of routers. 3. Network addresses available to transport layer use uniform numbering plan – even across LANs and WANs
- 7. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Implementation of Connectionless Service Routing within a datagram network ISP’s equipment
- 8. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Implementation of Connection-Oriented Service Routing within a virtual-circuit network ISP’s equipment A’s table C’s Table E’s Table
- 9. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Comparison of Virtual-Circuit and Datagram Networks Comparison of datagram and virtual-circuit networks
- 10. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Routing Algorithms (1) • Optimality principle • Shortest path algorithm • Flooding • Distance vector routing • Link state routing • Routing in ad hoc networks
- 11. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Routing Algorithms (2) • Broadcast routing • Multicast routing • Anycast routing • Routing for mobile hosts • Routing in ad hoc networks
- 12. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Fairness vs. Efficiency Network with a conflict between fairness and efficiency.
- 13. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Routing Algorithm type -- Non adaptive algorithm (Static ) - It do not base their routing decisions on any measurements or estimates of the current topology and traffic. -- Adaptive algorithm (Dynamic) - Adaptive algorithms, in contrast, change their routing decisions to reflect changes in the topology, and sometimes changes in the traffic as well.
- 14. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The Optimality Principle (a) A network. (b) A sink tree for router B. No Loop
- 15. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Shortest Path Algorithm (1) The first five steps used in computing the shortest path from A to D. The arrows indicate the working node
- 16. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Flooding a) A simple local technique is flooding, in which every incoming packet is sent out on every outgoing line except the one it arrived on. b) Flooding obviously generates vast numbers of duplicate packets c) Flooding is not practical for sending most packets, but it does have some important uses. First, it ensures that a packet is delivered to every node in the network. d) Flooding is tremendously robust.
- 17. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 (a) A network. (b) Input from A, I, H, K, and the new routing table for J. Distance Vector Routing
- 18. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The Count-to-Infinity Problem The count-to-infinity problem
- 19. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Link State Routing 1. Discover neighbors, learn network addresses. 2. Set distance/cost metric to each neighbor. 3. Construct packet telling all learned. 4. Send packet to, receive packets from other routers. 5. Compute shortest path to every other router.
- 20. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Learning about the Neighbors (1) Nine routers and a broadcast LAN.
- 21. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Learning about the Neighbors (2) A graph model of previous slide.
- 22. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Building Link State Packets (a) A network. (b) The link state packets for this network.
- 23. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 -- Too many packets present in the network causes packet delay and loss that degrades performance. This situation is called congestion. -- The network and transport layers share the responsibility for handling congestion. Since congestion occurs within the network, it is the network layer that directly experiences it and must ultimately determine what to do with the excess packets. However, the most effective way to control congestion is to reduce the load that the transport layer is placing on the network. -- This requires the network and transport layers to work together.
- 24. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Congestion Control Algorithms (1) • Approaches to congestion control • Traffic-aware routing • Admission control • Traffic throttling • Load shedding
- 25. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Congestion Control Algorithms (2) Link slow- Receiver Slow– Host slow down
- 26. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Approaches to Congestion Control Timescales of approaches to congestion control
- 27. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 • Network Provisioning - Links and Routers which are regularly heavily utilized are upgraded at the earliest. • Admission Control - Control the new added router in network - New connection can be refused
- 28. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic-Aware Routing - A network in which the East and West parts are connected by two links. - Bandwidth and Propagation dealy
- 29. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Throttling (1) (a) A congested network. (b) The portion of the network that is not congested. A virtual circuit from A to B is also shown.
- 30. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Throttling (2) Explicit congestion notification
- 31. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Load Shedding (1) A choke packet that affects only the source..
- 32. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Load Shedding (2) A choke packet that affects each hop it passes through.
- 33. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Quality of Service • Application requirements • Traffic shaping • Packet scheduling • Admission control • Integrated services • Differentiated services
- 34. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Scheduling (1) Kinds of resources can potentially be reserved for different flows: 1. Bandwidth. 2. Buffer space. 3. CPU cycles.
- 35. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Integrated Services (1) (a) A network. (b) The multicast spanning tree for host 1. (c) The multicast spanning tree for host 2.
- 36. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Integrated Services (2) (a) Host 3 requests a channel to host 1. (b) Host 3 then requests a second channel, to host 2. (c) Host 5 requests a channel to host 1.
- 37. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Differentiated Services (1) Expedited packets experience a traffic-free network
- 38. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Differentiated Services (2) A possible implementation of assured forwarding
- 39. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The Network Layer in the Internet (1) • The IP Version 4 Protocol • IP Addresses • IP Version 6 • Internet Control Protocols • Label Switching and MPLS • OSPF—An Interior Gateway Routing Protocol • BGP—The Exterior Gateway Routing Protocol • Internet Multicasting • Mobile IP
- 40. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The Network Layer in the Internet (2) The Internet is an interconnected collection of many networks.
- 41. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The IP Version 4 Protocol (1) The IPv4 (Internet Protocol) header.
- 42. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 The IP Version 4 Protocol (2) Some of the IP options.
- 43. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (1) An IP prefix.
- 44. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (2) Splitting an IP prefix into separate networks with subnetting.
- 45. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (3) A set of IP address assignments
- 46. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (4) Aggregation of IP prefixes
- 47. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (5) Longest matching prefix routing at the New York router.
- 48. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (6) IP address formats
- 49. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (7) Special IP addresses
- 50. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Addresses (8) Placement and operation of a NAT box.
- 51. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Version 6 Goals • Support billions of hosts • Reduce routing table size • Simplify protocol • Better security • Attention to type of service • Aid multicasting • Roaming host without changing address • Allow future protocol evolution • Permit coexistence of old, new protocols. . .
- 52. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Version 6 (1) The IPv6 fixed header (required).
- 53. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Version 6 (2) IPv6 extension headers
- 54. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Version 6 (3) The hop-by-hop extension header for large datagrams (jumbograms).
- 55. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 IP Version 6 (4) The extension header for routing.
- 56. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Internet Control Protocols (2) Two switched Ethernet LANs joined by a router
- 57. Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 End Chapter 6