1. 802.5 Token-Ring Networks: Topology An alternative to Ethernet 802.3 LANs Physical Layer Topology: Ring –Stations connected in a loop –Signals go in only one direction, station-to- station –Not bus physical layer topology like Ethernet 802.3

2. 802.5 TRN Physical Layer: Topology Access Unit STP link from Station to Access Unit Stations Station UTP Link from Station to Access Unit Physically, stations connect to access units which are connected in a ring

3. 802.5 TRN Physical Layer: Wiring Access Unit STP link between Access Units STP link from Station to Access Unit Stations Station UTP Link from Station to Access Unit Most connections use shielded twisted pair (STP), which has each pair and the whole cable covered with a metal shield to reduce interference

4. 802.5 TRN: Physical Speed 802.5 Speeds –Initially, 4 Mbps –Now, mostly 16 Mbps –100 Mbps is standardized but not widely used

5. 802.5 TRN MAC Layer: Token Passing Media Access Control –Not CSMA/CD –Token passing –Special frame called a token circulates –Station can only transmit if it has the token Token Transmits

6. Token-Ring Networks 802.5 Token-Ring versus 802.3 CSMA/CD-Bus –Token-Ring is more reliable –Token-Ring is more efficient –Token-Ring is more expensive –Token-Ring has a small market share –Companies buy something good enough to meet requirements, and 802.3 standards do this

7. 802.3 Ethernet versus 802.5 Token-Ring Network 802.3802.5 LLC 802.2 MAC Access Control CSMA/CDToken Passing PHY Topology BusRing Both use 802.2 Standard at the LLC Layer MAC Layer: CSMA/CD versus token- passing PHY Layer Topology: Bus versus Ring