User guide

Internetworking Primer A-21
Desktop Protocols
Routed Protocol Design Goals
Each of these three desktop protocols was designed with a common set of goals—unique
network numbering, node addressing, and data link address resolution, routing protocols,
and directory services. Understanding these goals, and how each desktop protocol solves
each goal, aids in the understanding, building, and administration of internetworks.
Unique Network Numbering
Every data link in your internetwork is given a unique network number. Every LAN
(Ethernet or Token Ring), and WAN is assigned its own unique network number for
identification. A bridged or switched LAN is only one network from the perspective of a
network protocol. Routers and access servers use these network numbers to route packets
within an internetwork. IP, IPX, and AppleTalk all use a similar model for assigning each
distinct network a unique network number. Network administrators must develop a
numbering plan for each protocol and control assignment of the unique network
numbering. Duplicate network numbers in a routed network will cause loss of connectivity.
More than one protocol can be implemented on a network. The numbering plan for each
network protocol is independent of the numbering plan used by other network protocols.
Figure A-8 illustrates a numbering plan for IP, IPX, and AppleTalk networks.