Bridging And The Etwmim - Cabletron Systems ETWMIM User Manual

Protocols
The ETWMIM supports the following transmission Protocols:
• Internet Protocol (IP)
• IPX
• AppleTalk
• Point to Point Protocol (LCP and BNCP), as defined by
RFC1331
• Frame Relay (RFC1490, ANSI T1.617 Annex D)

1.5 BRIDGING AND THE ETWMIM

The primary function of the ETWMIM is to bridge between different
transmission technologies (i.e., Ethernet, Token Ring, and Wide Area).
When the ETWMIM receives frames (traffic) from one of its
connections, it places the frames in buffer memory, and determines:
• the type of frames (depending on the receiving port)
• where the frames came from (source address), and if it has seen
frames from this address before (learning)
• where the frames are going (destination address), and if it has
received frames from this address before (filtering database
look-up)
• whether to forward (send on) or filter any of these frames
(database look-up result)
• what port/channel to use if it must forward the frames.
In the process of bridging traffic, the ETWMIM may have to translate
frames from one transmission type to another (e.g., Ethernet - Token
Ring, Token Ring - Ethernet), or encapsulate the frames for timed/
synchronous transmission (e.g., WAN PPP frame encapsulation).
INTRODUCTION
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