Chapter 4: Network Layer Chapter goals: Overview: o understand principles D network layer services behind network layer services: 口 hierarchical routing o routing(path selection) IP o dealing with scale O what's inside a router? o how a router works o advanced topics IPv6 O IPv6 multicast g instantiation and implementation in the Internet 4: Network Layer 4a-1
4: Network Layer 4a-1 Chapter 4: Network Layer Chapter goals: understand principles behind network layer services: routing (path selection) dealing with scale how a router works advanced topics: IPv6, multicast instantiation and implementation in the Internet Overview: network layer services hierarchical routing IP what’s inside a router? IPv6
Network layer functions o transport packet from pplication sending to receiving hosts g network layer protocols in network eve ery host, router data link physical ata link three important functions ●●● data link o path determination: route physical taken by packets from source network to dest. routing algorithms data link physical o switching: move packets from routers input to appropriate router output data link o call setup: some network architectures require router call setup along path before data flows 4: Network Layer 4a-2
4: Network Layer 4a-2 Network layer functions transport packet from sending to receiving hosts network layer protocols in every host, router three important functions: path determination: route taken by packets from source to dest. Routing algorithms switching: move packets from router’s input to appropriate router output call setup: some network architectures require router call setup along path before data flows network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical application transport network data link physical application transport network data link physical
Network service model Q: What service model for channel transporting packets The most important abstraction provided from sender to by network layer receiver? s o guaranteed bandwidth? virtual circuit t o preservation of inter-packet or timing(no jitter)? datagram? go loss-free delivery o in-order delivery? 5 o congestion feedback to sender? 4: Network Layer 4a-3
4: Network Layer 4a-3 Network service model Q: What service model for “channel” transporting packets from sender to receiver? guaranteed bandwidth? preservation of inter-packet timing (no jitter)? loss-free delivery? in-order delivery? congestion feedback to sender? ? ? ? virtual circuit or datagram? The most important abstraction provided by network layer:
Virtual circuits source-to-dest path behaves much like telephone circuit o performance-WIse o network actions along source-to-dest path o call setup, teardown for each call before data can flow D each packet carries VC identifier(not destination host OD) o every router on source-dest path s maintain state"for each passing connection o transport-layer connection only involved two end systems o link, router resources(bandwidth, buffers)may be allocated to vc o to get circuit-like perf 4: Network layer 4a-4
4: Network Layer 4a-4 Virtual circuits call setup, teardown for each call before data can flow each packet carries VC identifier (not destination host OD) every router on source-dest path s maintain “state” for each passing connection transport-layer connection only involved two end systems link, router resources (bandwidth, buffers) may be allocated to VC to get circuit-like perf. “source-to-dest path behaves much like telephone circuit” performance-wise network actions along source-to-dest path
Virtual circuits: signaling protocols D used to setup maintain teardown Vc O used in ATM, frame-relay, X25 g not used in today' s Internet applICaTion transport 5, Data flow begins 6. Receive data ap application network 4.Call connected transpon↑ 3. Accept ce data link 1 Initiate call network 2. incoming c data link physIca physical 4: Network Layer 4a-5
4: Network Layer 4a-5 Virtual circuits: signaling protocols used to setup, maintain teardown VC used in ATM, frame-relay, X.25 not used in today’s Internet application transport network data link physical application transport network data link physical 1. Initiate call 2. incoming call 4. Call connected 3. Accept call 5. Data flow begins 6. Receive data