Where We Are So Far… EECS 122, Lecture 18 Today’s Topics: • Networking concepts – remote access to resources Review of Where We Are – controlled sharing Introduction to Transport Layer • multiplexing: TDM, Stat Mux UDP: The User Datagram Protocol – protocols and layering • ISO reference model, encapsulation Introduction to Reliability • service model, error detection • end-to-end argument • soft state Kevin Fall,
[email protected] Where We Are So Far… Where We Are So Far… • Development of the Internet • Direct-link networks – interconnection of heterogeneous networks – signals, modulation, error detection – simple best-effort service model – best-effort delivery between attached – fully-connected graph of hosts (routing) stations – possible error correction using codes • Internet scaling issues – MAC protocols, Ethernet – use of hierarchies in routing, addresses, DNS – use of caching in DNS Where We Are So Far… What We Are Missing… • The Internet Protocol • Access to process-level information – IP service model – currently, can only send traffic from one • best-effort datagram model computer to another • error detection in header only – no way to indicate which process or service • consistent, abstract packet, addressing should receive it • routing • Reliable transport • signaling (ICMP) – no way to know whether data received was • multicasting, IGMP, multicast routing correct • IP futures with IPv6 – no way to correct for delivery errors 1 Problem Set #3 The Transport Layer • Peterson & Davie: • provide application-to-application