Interplay between routing and forwarding routing algorithm local forwarding table header value output link 0100 0101 2 0111 1001 value in arriving packet's header 0111 Network Layer 4-6
Network Layer 4-6 1 2 3 0111 value in arriving packet’s header routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 2 1 Interplay between routing and forwarding
Connection setup 3rd important function in some network architectures: ATM,frame relay,X.25 before datagrams flow,two end hosts and intervening routers establish virtual connection o routers get involved network vs transport layer connection service: o network:between two hosts(may also involve inervening routers in case of VCs) o transport:between two processes Network Layer 4-7
Network Layer 4-7 Connection setup 3 rd important function in some network architectures: ATM, frame relay, X.25 before datagrams flow, two end hosts and intervening routers establish virtual connection routers get involved network vs transport layer connection service: network: between two hosts (may also involve inervening routers in case of VCs) transport: between two processes
Network service model Q:What service model for "channel"transporting datagrams from sender to receiver? Example services for Example services for a individual datagrams: flow of datagrams: ▣guaranteed delivery in-order datagram ▣guaranteed delivery delivery with less than 40 msec ▣guaranteed minimum delay bandwidth to flow ▣restrictions on changes in inter- packet spacing Network Layer 4-8
Network Layer 4-8 Network service model Q: What service model for “channel” transporting datagrams from sender to receiver? 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 interpacket spacing
Network layer service models: Network Service Guarantees Congestion Architecture Model Bandwidth Loss Order Timing feedback Internet best effort none no no no no(inferred via loss) ATM CBR constant yesyes yes no rate congestion ATM VBR guaranteed yes yes yes no rate congestion ATM ABR guaranteed no yes no yes minimum ATM UBR none no yes no no Network Layer 4-9
Network Layer 4-9 Network layer service models: Network Architecture Internet ATM ATM ATM ATM Service Model best effort CBR VBR ABR UBR Bandwidth none constant rate guaranteed rate guaranteed minimum none Loss no yes yes no no Order no yes yes yes yes Timing no yes yes no no Congestion feedback no (inferred via loss) no congestion no congestion yes no Guarantees ?
Chapter 4:Network Layer ▣4.1 Introduction 4.5 Routing algorithms 4.2 Virtual circuit and o Link state datagram networks o Distance Vector 4.3 What's inside a o Hierarchical routing router 4.6 Routing in the ▣4.4IP:Internet Internet Protocol o RIP o Datagram format o OSPF o IPv4 addressing o BGP o ICMP ▣4.7 Broadcast and o IPv6 multicast routing Network Layer 4-10
Network Layer 4-10 Chapter 4: Network Layer 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What’s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing ICMP IPv6 4.5 Routing algorithms Link state Distance Vector Hierarchical routing 4.6 Routing in the Internet RIP OSPF BGP 4.7 Broadcast and multicast routing