1. Layer Models ISO 7 layer Model IEEE Model DOD Model ATM TCP Protocol Suit Communication Reference Models

2. Layer Models General Upper LayerPeer Layerprotocol Service Layer Service request Service delivery Service Layer Service request Service delivery Alternative implementations protocol

3. Layer Message Format Layer 3 Layer 2 payload Layer 1 H2 t2payload H3t3 H2 t2payload

4. ISO 7-layer model –1 physicaltransmit signals –2 data linkreliable point to point –3 networkrouting –4 transport end to end –5 sessionlogon, security –6 presentationintegers,characters –7 apps --> ftp, email, telnet,WWW

5. IEEE model for LANs compatible with ISO; more detail for specific type of networks -> Application -> LLC - logical link control -> MAC - medium access control -> physical layer/medium ISO LAYER 7,6,5,3 2 1

6. LANs : local area networks ethernet, or CSMA/CD : IEEE 802.3 –most widely used LAN; more than half of all LANs in the world –broadcast-contention protocol –data rates of 10,100,1000 Mbps –physically configured as bus or a star –can use coax cable (thick or thin), twisted pair, or optical fiber. –utilization of 30-50%, roughly

7. ethernet ethernet topology: original topology was bus, as above. Signals broadcast in both directions to all receivers. can also be configured as tree, but uses same protocol.

8. LANs : local area networks token ring : IEEE 802.5 –2nd most used in internet; 20-25% of all LANs. –physical ring, logical broadcast; no collisions. –data rates 4,16,100 (FDDI) –throughput 90-95% entirely possible

9. token ring data flows in 1 direction around the ring, from station to station only 1 station, which possesses token, allowed to transmit; all others repeat.

10. DOD Model Internetworking –applications : email, FTP, telnet, WWW –host-host --> transport layer: TCP,UDP –internet layer : IP –network interface --> to lower layered networks; eg, ethernet, token ring, FDDI, MILNet, etc. –Physical ISO LAYER 7,6,5, 4 3 2 1

11. TCP/IP protocol suite IP TCPUDP LAN/WAN media IGMPICMP RARP ARP telnet, FTP, etc. TFTP, other apps. apps

12. ATM model ATM: asynchronous transfer mode high speed network layers: physical -- based on optical fiber ATM layer -- switching ATM adoption layer - interface user layers