Advanced Computer Networks: Lecture 45. This lecture will cover the following: global internets; diameter of the internet; internet structure today; multiple backbone service providers; arbitrary graph structure; virtual geographies; scaling problems for the internet; IP address hierarchy evolution;...
CS716 Advanced Computer Networks By Dr. Amir Qayyum 1 Lecture No. 45 Where we are What we understand • Concepts of networking & network programming – Elements of networks: nodes and links – Building a packet abstraction on a link • Issues related to bits/frames sent on a single link – How to detect transmission errors in a frame after encoding and framing it – How to simulate a reliable channel (sliding window) – How to arbitrate access to shared media in any network • Design issues of direct link networks – Functionality of network adaptors Where we are – What we understand • How switches may provide indirect connectivity – – – – Different ways to move through a network (forwarding) Bridge approach to extending LAN concept Example of a real virtual circuit network (ATM) How switches are built and contention within switches • How different networks work together – (Common connecting protocol IP) and its service model – Routing protocols in simple networks • Next: large networks working together Internetworking • Reading: Peterson and Davie, Chapter 4 • Global internets (scale) • Dealing with global scale – Virtual geography and addresses – Hierarchical routing – Multicast traffic – MPLS • Future internetworking: IPv6 How Should Hierarchy be Defined ? • Hierarchy reduces information requirements for forwarding Internetworking • Main problems addressed by internetworking – Heterogeneity – Scale • Bridges scale to level of medium organization • IP addresses most endtoend heterogeneity issues • Today: issues of global scale Global Internets • Evolution of Internet structure • Virtual geographies: networks, domains, and translations • Problems of scale • IP address hierarchy evolution • Notion of autonomous systems (AS’s) • Common intradomain routing protocols • Standard interdomain routing protocol Diameter of the Internet • Connect all nodes of a network in a big ring – Network diameter will be half the ring circumference • Adding more links brings down network diameter – Diameter can be quarter of the ring with one link … How many links should be added to bring the diameter below some threshold ? Internet Structure in Recent Past 1990 NSFNET backbone Stanford BARRNET regional Berkeley PARC MidNet regional … Westnet regional UNM NCAR ISU UNL KU UA • Tree structure, centered around one backbone • Interconnection of thousands of “organizations” – End users and service providers • Scalability of routing protocols in global Internet – Network entities are administratively independent 10 Communication Through SIP Proxies cisco.com proxy bsd-pc.cisco com bruc e@cisco.com princet on.edu proxy llp-ph cs.princeton.edu larry@princeton.edu 471 Message Flow for a SIP Session bsdpc.cisco.com cisco.com provxy princeton.e du proxy llpph.cs.princeton.edu invite 100 trying invite 100 trying invite 180 ringing ringin g 180 ringing ringin g 180 ringing ringin g 200 OK 200 OK 200 OK ACK Media BY E 200 OK 472 Devices in H.323 Network Conventional telephone network H.323 gatekeeper H.323 terminal H.323 gateway H.323 terminal 473 Overlay Networks 474 Overlay Network Layered on Top of a Physical Network 475 Overlay Nodes Tunnel Through Physical Nodes IHdr IHdr A IHdr B OHdr IHdr C OHdr IHdr 476 A R1 B Multicast Trees Mapped Onto a Physical Topology 50 C D R2 (a) A C R1 R2 B D (b) A C R1 R2 B D (c) A C R1 R2 B D (d) 477 Multicast Tree Embedded in an Overlay Mesh A C B D A C B D 478 Triangular Inequality in Networks 10 70 125 479 Peer to Peer Network 480 128bit Nodes and Objects ID Space 2128 objid nodeids 481 Locating Object by Routing d471f1 d46a1c d467c4 d462ba d4213f d13da3 65a1fc locate(d46a1c) 482 Routing Table at Nodes 483 Adding Node to the Network d471f1 d46a1c d467c4 d462ba d4213f addnode(d46a1c) d13da3 65a1fc 484 Content Distribution Network Site A Site B Site C aaa.com bbb.com ccc.com Backend servers Cache Geographically distributed surrogate servers Redirectors Clients 485 .. .Lecture? ?No.? ?45 Where we are What we understand • Concepts of networking & network programming – Elements of? ?networks:? ?nodes and links – Building a packet abstraction on a link... Virtual geography and addresses – Hierarchical routing • Future internetworking: IPv6 • Multicast traffic • MPLS 45 IPv6 History • Nextgeneration IP, previously denoted IPng • Intended to extend address space/routing limitations