计算机网络第五版英文第五章 网络层ppt课件.ppt

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1、Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,The Network Layer,Chapter 5,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Network Layer Design Issues,Store-and-forward pa

2、cket switchingServices provided to transport layerImplementation of connectionless serviceImplementation of connection-oriented serviceComparison of virtual-circuit and datagram networks,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,S

3、tore-and-Forward Packet Switching,The environment of the network layer protocols.,ISPs equipment,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Services Provided to the Transport Layer,Services independent of router technology.Transpor

4、t layer shielded from number, type, topology of routers.Network addresses available to transport layer use uniform numbering planeven across LANs and WANs,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Implementation of Connectionless

5、Service,Routing within a datagram network,ISPs equipment,As table (initially) As table (later) Cs Table Es Table,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Implementation of Connection-Oriented Service,Routing within a virtual-circ

6、uit network,ISPs equipment,As table Cs Table Es Table,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,Computer Networks, Fifth Editi

7、on by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Routing Algorithms (1),Optimality principleShortest path algorithmFloodingDistance vector routingLink state routingRouting in ad hoc networks,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pe

8、arson Education-Prentice Hall, 2011,Routing Algorithms (2),Broadcast routingMulticast routingAnycast routingRouting for mobile hostsRouting in ad hoc networks,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Fairness vs. Efficiency,Netwo

9、rk with a conflict between fairness and efficiency.,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.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wet

10、herall, 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,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Shortes

11、t Path Algorithm (2),Dijkstras algorithm to compute the shortest path through a graph.,. . .,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Shortest Path Algorithm (3),Dijkstras algorithm to compute the shortest path through a graph.,.

12、 . .,. . .,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Shortest Path Algorithm (4),Dijkstras algorithm to compute the shortest path through a graph.,. . .,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pea

13、rson Education-Prentice Hall, 2011,(a) A network. (b) Input from A, I, H, K, and the new routing table for J.,Distance Vector Routing,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,The Count-to-Infinity Problem,The count-to-infinity pr

14、oblem,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Link State Routing,Discover neighbors, learn network addresses.Set distance/cost metric to each neighbor.Construct packet telling all learned.Send packet to, receive packets from oth

15、er routers.Compute shortest path to every other router.,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.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David We

16、therall, Pearson Education-Prentice Hall, 2011,Learning about the Neighbors (2),A graph model of previous slide.,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 t

17、his network.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Distributing the Link State Packets,The packet buffer for router B in previous slide,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Educatio

18、n-Prentice Hall, 2011,Hierarchical Routing,Hierarchical routing.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Broadcast Routing,Reverse path forwarding. (a) A network. (b) A sink tree. (c) The tree built by reverse path forwarding.,C

19、omputer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Multicast Routing (1),(a) A network. (b) A spanning tree for the leftmost router. (c) Amulticast tree for group 1. (d) A multicast tree for group 2.,Computer Networks, Fifth Edition by Andr

20、ew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Multicast Routing (2),Core-based tree for group 1.Sending to group 1.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Anycast Routing,Anycast routes to group 1. Top

21、ology seen by the routing protocol.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Routing for Mobile Hosts,Packet routing for mobile hosts,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Pre

22、ntice Hall, 2011,Routing in Ad Hoc Networks,Range of As broadcast. After B and D receive it. After C, F, and G receive it.After E, H, and I receive it.,The shaded nodes are new recipients. The dashed lines show possible reverse routes. The solid lines show the discovered route.,Computer Networks, Fi

23、fth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Congestion Control Algorithms (1),Approaches to congestion controlTraffic-aware routingAdmission controlTraffic throttlingLoad shedding,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall,

24、 Pearson Education-Prentice Hall, 2011,Congestion Control Algorithms (2),When too much traffic is offered, congestion sets in and performance degrades sharply.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Approaches to Congestion Con

25、trol,Timescales of approaches to congestion control,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.,Computer Networks, Fifth Edition by Andrew

26、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.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Ed

27、ucation-Prentice Hall, 2011,Traffic Throttling (2),Explicit congestion notification,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.,Computer Networks, Fifth Edition by Andre

28、w Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Load Shedding (2),A choke packet that affects each hop it passes through.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Quality of Service,Application requirements

29、Traffic shapingPacket schedulingAdmission controlIntegrated servicesDifferentiated services,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Application Requirements (1),How stringent the quality-of-service requirements are.,Computer Net

30、works, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Categories of QoS and Examples,Constant bit rateTelephonyReal-time variable bit rateCompressed videoconferencingNon-real-time variable bit rateWatching a movie on demandAvailable bit rate File transfe

31、r,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Traffic Shaping (1),(a) Shaping packets. (b) A leaky bucket. (c) A token bucket,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall,

32、 2011,Traffic Shaping (2),(a) Traffic from a host. Output shaped by a token bucket of rate 200 Mbps and capacity (b) 9600 KB, (c) 0 KB.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Traffic Shaping (3),Token bucket level for shaping w

33、ith rate 200 Mbps and capacity (d) 16000 KB, (e) 9600 KB, and (f) 0KB.,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: Bandwidth. Buffer space. CP

34、U cycles.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Scheduling (2),Round-robin Fair Queuing,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Scheduling (

35、3),Weighted Fair Queueing.Finishing times for the packets.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Admission Control (1),An example flow specification,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pea

36、rson Education-Prentice Hall, 2011,Admission Control (2),Bandwidth and delay guarantees with token buckets and WFQ.,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 f

37、or host 1. (c) The multicast spanning tree for host 2.,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 req

38、uests a channel to host 1.,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,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson

39、 Education-Prentice Hall, 2011,Differentiated Services (2),A possible implementation of assured forwarding,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Internetworking,How networks differHow networks can be connectedTunnelingInternet

40、work routingPacket fragmentation,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,How Networks Differ,Some of the many ways networks can differ,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-P

41、rentice Hall, 2011,How Networks Can Be Connected,A packet crossing different networks. Network and link layer protocol processing.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Tunneling (1),Tunneling a packet from Paris to London.,Co

42、mputer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Tunneling (2),Tunneling a car from France to England,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmentation (1),

43、Packet size issues:HardwareOperating systemProtocolsCompliance with (inter)national standard.Reduce error-induced retransmissionsPrevent packet occupying channel too long.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmenta

44、tion (2),Transparent fragmentation. Nontransparent fragmentation,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmentation (3),Fragmentation when the elementary data size is 1 byte.(a) Original packet, containing 10 data byte

45、s.,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmentation (4),Fragmentation when the elementary data size is 1 byte(b) Fragments after passing through a networkwith maximum packet size of 8 payload bytes plus header.,Compu

46、ter Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmentation (5),Fragmentation when the elementary data size is 1 byte(c) Fragments after passing through a size 5 gateway.,Computer Networks, Fifth Edition by Andrew Tanenbaum and Davi

47、d Wetherall, Pearson Education-Prentice Hall, 2011,Packet Fragmentation (6),Path MTU Discovery,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,The Network Layer Principles (1),Make sure it worksKeep it simpleMake clear choicesExploit mo

48、dularityExpect heterogeneity . . .,Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, Pearson Education-Prentice Hall, 2011,The Network Layer Principles (2),. . .Avoid static options and parametersLook for good design (not perfect)Strict sending, tolerant receivingThink about

49、scalabilityConsider performance and cost,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 ProtocolIP AddressesIP Version 6Internet Control ProtocolsLabel Switching and MPLSOSPFAn Int

50、erior Gateway Routing ProtocolBGPThe Exterior Gateway Routing ProtocolInternet MulticastingMobile IP,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 m