1. School of Information Technologies Revision NETS3303/3603 Week 13

2. School of Information Technologies Overall Understand WHY protocols were designed the way they were Understand what is good and bad with the designs Appreciate how to implement network services: client/server and peer-to-peer

3. School of Information Technologies Layered Model Divide a task into pieces and then solve each piece independently (or nearly so). Establishing a well defined interface between layers makes porting easier Major Advantages:  Modularity  Extensibility  Maintainability

4. School of Information Technologies TCP/IP Model Physical Encoding Data-link Framing Local Addressing Network Global Addressing Packetisation Transport End-to-end flow control Multiplexing Application Allow access Session Management Example functions In different layers

5. School of Information Technologies Data-link Layer Provides access to local network/link Supplies physical addressing Transports traffic over one hop only Many different technologies with different characteristics Wired and wireless

6. School of Information Technologies Internet Layer IP provides connectionless, unreliable delivery of datagrams IP addressing provide global unique identification Address shortage => CIDR, NAT to rescue! Routing service: intra and inter-AS

7. School of Information Technologies ICMP “Companion” to IP, used for queries and error signalling Common usage: –Host or network unreachable –Redirect –Echo request/reply (ping)

8. School of Information Technologies Other Internet Layer Services Multicasting –Group membership: IGMP –Data delivery: multicast routing protocols Quality of service: –Admission Control, Resource Reservation, Queueing and Scheduling –IntServ, DiffServ

9. School of Information Technologies Transport Layer User Datagram Protocol, UDP adds: –Multiplexing (ports) –Error detection (checksum) Transport Control Protocol, TCP also adds: –Error correction –Flow control –Congestion Control

10. School of Information Technologies TCP Characteristics Connection oriented –Three way handshake Reliable –Error detection –Error correction Buffer management and flow control –Sliding window –Slow Start and Congestion Avoidance Stream oriented

11. School of Information Technologies Types of Traffic Different applications generate different types of traffic e.g. –Web pages (delay sensitive) –FTP (BW sensitive) –Streamed Media (BW sensitive) –Conversational Multimedia (delay and BW)

12. School of Information Technologies RTP TCP unsuitable for RT media UDP has two major drawbacks: –Lack support for lost or reordered packets –Lack support for jitter compensation RTP provides these functions with RTCP SIP and H.323 provides signalling for session management

13. School of Information Technologies Future of Networks Wireless networking –Inter-vehicular system, building monitoring, habitat monitoring, structural monitoring, emergency rescue, battlefield surveillance –Needs low-power and robust protocols Interplanetary Internet –A set of floating nodes in space which can communicate with each other –Needs a new set of protocols and technology that are tolerant to large delays

14. School of Information Technologies Some Hints for Finals Bring CALCULATOR! 5 questions Core topics: –Distributed system models –IP layer issues (addressing, ICMP, NAT) –Routing Protocols and Architecture –TCP –Multicasting –QoS –RTP, RTCP

15. School of Information Technologies The End!