Lectures 24&25 Higher Layer Protocols: TCP/IP and atm Eytan Modiano Massachusetts Institute of Technology Laboratory for Information and Decision Systems
Lectures 24 & 25 Higher Layer Protocols: TCP/IP and ATM Eytan Modiano Massachusetts Institute of Technology Laboratory for Information and Decision Systems Eytan Modiano Slide 1
Outline Network Layer and Internetworking The TCP/IP protocol suit ATM MPLS
Outline • Network Layer and Internetworking • The TCP/IP protocol suit • ATM • MPLS Eytan Modiano Slide 2
Higher Layers Application Application irtual network service Presentation Presentation Virtual session Virtual link for end to end messages Transport Transport TCP, UDP Virtual link for end to end packet Network Network Network IP. ATM Virtual link for eliable packets Data link Data link LC DLCLDLC Control Virtual bit pipe physical nt. phys. int interface ysical link External subnet subnet External node
Higher Layers Virtual link for reliable packets Application Presentation Session Transport Network Data link Control Application Presentation Session Transport Network Data link Control Network Network DLC DLC DLC DLC Virtual bit pipe Virtual link for end to end packets Virtual link for end to end messages Virtual session Virtual network service physical phys. int. phys. int. phys. int. phys. int. interface physical interface TCP, UDP IP, ATM Physical link External subnet subnet External Site node node site Eytan Modiano Slide 3
Packet Switching Datagram packet switching Route chosen on packet-by-packet basis Different packets may follow different routes Packets may arrive out of order at the destination E.g., IP(The Internet Protocol Virtual Circuit packet switching All packets associated with a session follow the same path Route is chosen at start of session Packets are labeled with a vc# designating the route The vc number must be unique on a given link but can change from link to link Imagine having to set up connections between 1000 nodes in a mesh Unique vc numbers imply 1 Million vc numbers that must be represented and stored at each node E.g., ATM(Asynchronous transfer mode)
Packet Switching • Datagram packet switching – Route chosen on packet-by-packet basis – Different packets may follow different routes – Packets may arrive out of order at the destination – E.g., IP (The Internet Protocol) • Virtual Circuit packet switching – All packets associated with a session follow the same path – Route is chosen at start of session – Packets are labeled with a VC# designating the route – The VC number must be unique on a given link but can change from link to link Imagine having to set up connections between 1000 nodes in a mesh Unique VC numbers imply 1 Million VC numbers that must be represented and stored at each node – E.g., ATM (Asynchronous transfer mode) Eytan Modiano Slide 4
Virtual Circuits Packet Switching For datagrams, addressing information must uniquely distinguish each network node and session Need unique source and destination addresses For virtual circuits, only the virtual circuits on a link need be distinguished by addressing Global address needed to set-up virtual circuit Once established. local virtual circuit numbers can then be used to represent the virtual circuits on a given link: Vc number changes from link to link VC7 VC4 9 VC13 Merits of virtual circuits Save on route computation VC3 VC7 Need only be done once VC3 at start of session Save on header size Node 5 table More complex Less flexible (35)vc13→(5,8)Vc3 (35)Vc7→(5,8)Vc4 (6,5) Vc3→(5,8)VC7
Virtual Circuits Packet Switching • For datagrams, addressing inf ormation must uniquely distinguish each network node and session – Need unique source and destination addresses • For virtual circuits, only the virtual circuits on a link need be distinguished by addressing – Global address needed to set-up virtual circuit – Once established, local virtual circuit numbers can then be used to represent the virtual circuits on a given link: VC number changes from link to link • Merits of virtual circuits – Save on route computation Need only be done once at start of session – Save on header size – More complex – Less flexible 3 6 5 8 2 9 VC3 VC13 VC7 VC4 VC3 VC7 Node 5 table (3,5) VC13 -> (5,8) VC3 (3,5) VC7 -> (5,8) VC4 (6,5) VC3 -> (5,8) VC7 Eytan Modiano Slide 5