Metropolitan Area Networks (MANs)

1. MANs are networks designed to extend over an entire city.

2. Uses IEEE 802.6 distributed queue dual bus (DQDB)
   • Each device connects to two backbone links where access is granted by distributed queues.

   • Data travel as 53-byte slots

   • Source station choses the bus for which the destination is considered downstream

   • To send data on one bus, a station must make a reservation on the other bus.

   • Physical layer specifications are left open

   • Access media can be either coaxial or fiber optic with a variety of data rates

3. Switched multimegabit data services (SMDS) is a service for handling high-speed communications for MANs.
   • Packet switched datagram service, therefore subscribers only pay for the time they use.

   • Subscriber LANs link to an SMDS network through routers that are connected to switches using DQDB architecture.

   • Access is coordinated through the SMDS interface protocol (SIP).

   • Can also be used as a WAN

   • Can receive and encapsulate frames from all LANs

   • Data rate ranges from 1.544 Mbps to 155 Mbps, each user is assigned an average data rate

   • Addressing system is a telephone number

   • Multicasting is available