1. 1 IEEE 802 LANs Following the success of CDMA technologies ALOHA & Ethernet, IEEE standardized CDMA/CD technology as IEEE 802.3 LAN Also standardized are many of the other broadcast technologies: Token Bus (802.4), Token Ring (802.5), Wireless LAN, a.k.a, WiFi (802.11)… Standards define –A Link Layer, called Logical Link Control (LLC) – same for all standards –A MAC layer (CSMA/CD for 802.3, Token Passing for 802.4 and 802.5, CSMA/CA for 802.11 etc.) –A Physical Layers & the link (physical medium) over which the PL will run, e.g., twisted-pair, coax, fiber, wireless (several PLs are defined for each staqndard)  LL & MAC are strictly tied to a PL Logical Link Layer (LLC) – 802.2 Medium Access Control (MAC) Physical Layer LL PL Link (Medium) Scope of IEEE 802 standards

2. 2 802.2 – LLC Service Interface Operation and format is based on HDLC Can be run to export any of the following service interfaces: –Unacknowledged connectionless service Unreliable, unordered frame delivery -- Ethernet –Connection-mode service Reliable, ordered frame delivery, flow control –Acknowledged connectionless service Reliable, unordered frame delivery

3. 3 802.3 MAC –CSMA/CD Physical Layer –10Base2: 10Mbps, Baseband coax – 200 meters max length –10BaseT: 10Mbps, Unshielded Twisted Pair. Also 100BaseT, 1000BaseT –Shielded Twisted Pair – 100 Mbps –Broadband coax – 10Mbps –Optical Fiber – 10Mbps, 100Mbps, 1Gbps Topology –Can be any one of Bus, Tree, Star star nodes Bus terminator nodes tree headend

4. 4 802.2/802.3 Frame Format (RFC 1042) DSAP AA Dest MAC Source MAC 802.3 66 2 SSAP AA Org code 00 Cntl 03 type CRC data 1 1 132 38-1492 4 802.2 LLC 802.2 SNAP Dest MAC Source MAC 66 2 CRC data 46-1500 4 length type Ethernet Encapsulation (RFC 894) IP Datagram (46-1500) Type 0800 ARP Request/Reply (28) Type 0806 Pad(18) IP Datagram (46-1500) Type 0800 ARP Request/Reply (28) Type 0806 Pad(18) None of the “type” fields in RFC 894 is within the valid “length” range in 802.3. So both formats can easily be distinguished

5. 5 802.4 – Token Bus Broadband coaxial cable 13 11719 17 14 20 Used in factory automation centers (assembly line) Logically stations are organized into a ring with each node knowing the address of the station to its “left” and “right”. When the logical ring is initialized, the highest numbered station has the “token”  It may send data When done, it passes the “token” to its immediate neighbor and so on. Clearly no collisions as only the station that has the token can transmit

6. 6 802.5 – Token Ring, FDDI Unidirectional ring Ring is in fact not a broadcast medium, but a collection of point-to-point links A station must own the “token” to transmit A transmitting station removes the bits of its frame after they circulate around the ring Length of the ring? An important design parameter

7. 7 802.11 - Wireless LAN 802.11b –2.4-5 GHz unlicensed radio spectrum –up to 11 Mbps –direct sequence spread spectrum (DSSS) in physical layer all hosts use same chipping code –widely deployed, using base stations 802.11a –5-6 GHz range –up to 54 Mbps 802.11g –2.4-5 GHz range –up to 54 Mbps All use CSMA/CA for multiple access All have base-station and ad-hoc network versions