《计算机网络 Computer Networking》课程PPT教学课件（A Top Down Approach，8th edition）Chapter 4 The Network Layer - Data Plane

Chapter 4 James F.Kurose Keith W.Ross Network Layer: Data Plane A note on the use of these PowerPoint slides: We're making these slides freely available to all(faculty,students, readers).They're in PowerPoint form so you see the animations;and can add,modify,and delete slides (including this one)and slide content to suit your needs.They obviously represent a lot of work on our part. COMPUTER In return for use,we only ask the following: NETWORKING If you use these slides(e.g.,in a class)that you mention their A TOP-DOWN APPROACH source(after all,we'd like people to use our book!) If you postany slides on a www site,that you note that they are adapted from(or perhaps identical to)our slides,and note our copyright of this material. Computer Networking:A For a revision history,see the slide note for this page. Top-Down Approach Thanks and enjoy!JFK/KWR 8th edition All material copyright 1996-2020 Jim Kurose,Keith Ross J.F Kurose and K.W.Ross,All Rights Reserved Pearson,2020

Computer Networking: A Top-Down Approach 8 th edition Jim Kurose, Keith Ross Pearson, 2020 Chapter 4 Network Layer: Data Plane A note on the use of these PowerPoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: ▪ If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!) ▪ If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. For a revision history, see the slide note for this page. Thanks and enjoy! JFK/KWR All material copyright 1996-2020 J.F Kurose and K.W. Ross, All Rights Reserved

Network layer:our goals -understand principles instantiation,implementation behind network layer in the Internet services,focusing on data ·IP protocol plane: ·NAT,middleboxes network layer service models forwarding versus routing ·how a router works ·addressing generalized forwarding Internet architecture NetworkLayer:4-2

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

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 Generalized Forwarding,SDN ·datagram format ·Match+action ·addressing OpenFlow:match+action in action network address translation ·1PV6 ■Middleboxes Network Layer:4-3

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

Network-layer services and protocols transport segment from sending mobile network to receiving host national or global ISP sender:encapsulates segments into datagrams,passes to link layer application receiver:delivers segments to transport network transport layer protocol link physical network layer protocols in every Internet device:hosts,routers ■routers: datacente examines header fields in all IP network datagrams passing through it application moves datagrams from input ports to ransport etwork output ports to transfer datagrams enterprise link network physical along end-end path Network Layer:4-4

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

Two key network-layer functions network-layer functions: analogy:taking a trip forwarding:move packets from forwarding:process of getting a router's input link to through single interchange appropriate router output link routing:process of planning trip routing:determine route taken from source to destination by packets from source to destination ·routing algorithms forwarding routing Network Layer: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 ▪ routing: determine route taken from source to destination by packets from source to destination • routing algorithms Network Layer: 4-5

Network layer:data plane,control plane Data plane: Control plane local,per-router function ■network-wide logic determines how datagram determines how datagram is arriving on router input port routed among routers along end- is forwarded to router end path from source host to output port destination host values in arriving two control-plane approaches: packet header traditional routing algorithms: implemented in routers software-defined networking(SDN): implemented in(remote)servers Network Layer:4-6

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

Per-router control plane Individual routing algorithm components in each and every router interact in the control plane Routing Algorithm control plane data header output plane values in arriving packet header 0111 Network Layer:4-7

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

Software-Defined Networking(SDN)control plane Remote controller computes,installs forwarding tables in routers Remote Controller control plane data plane CA values in arriving packet header 0111 NetworkLayer:4-8

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

Network service model Q:What service mode/for "channel"transporting datagrams from sender to receiver? example services for example services for a flow of individual datagrams: datagrams: guaranteed delivery in-order datagram delivery guaranteed delivery with guaranteed minimum bandwidth less than 40 msec delay to flow restrictions on changes in inter- packet spacing Network Layer:4-9

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

Network-layer service model Network Quality of Service(QoS)Guarantees Service Architecture Model Bandwidth Loss Order Timing Internet best effort none no no no Internet "best effort"service model No guarantees on: i.successful datagram delivery to destination ii.timing or order of delivery iii.bandwidth available to end-end flow Network Layer:4-10

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