HP 200 Series Services And Applications page 248

Shining a Light on FDDI
Internetworking with HP Routers
FDDI Translation Bridging
To ensure multivendor interoperability, the bridge protocol should be based
on the IEEE 802.1 Spanning Tree Protocol. Translation is required when
bridging between LANs with different data-link-layer characteristics. For
example, forwarding from an Ethernet to an 802.3 end station requires a
translation. When bridging Ethernet or 802.3 packets to FDDI media, a
MAC-layer translation is also required.
The 802.1 standards define how a received packet is formatted for transfer
across an intervening LAN (802.x or FDDI) and presented to a destination
LAN. In general, Ethernet Version 2 frames are encapsulated according to
rules specified in RFC 1042, and then converted back to Ethernet format.
IEEE 802.3/802.2 LLC and 802.3/LLC+SNAP remain unchanged when trans-
ferred across an intervening LAN. Table 1 summarizes translation rules.
Table 2 summarizes protocol-specific translation.
Table 1. Translation Rules for Encapsulation
Table 2. Protocol Translation and Encapsulation
Protocol
XNS
DECnet Phase IV
Novell
Novell
AppleTalk Phase 2
Source Routing
IP
IP
3-54
Source Network
Encapsulation Translation Rules
Ethernet
(SNAP OUI 00-00-00)
802.3/LLC + SNAP FDDI LLC + SNAP
802.3/802.2 LLC FDDI 802.2 LLC
Source Type
Ethernet
Ethernet
Proprietary
Ethernet
LLC+SNAP
802.2 LLC
Ethernet
LLC+SNAP
Destination Network
Encapsulation
RFC 1042 Ethernet
802.3/LLC + SNAP
802.3/802.2 LLC
Translation Rules Destination Type
RFC 1042 Ethernet
RFC 1042 Ethernet
RFC 1042 Ethernet
RFC 1042 Ethernet
LLC + SNAP LLC + SNAP
802.2 LLC 802.2 LLC
RFC 1042 Ethernet
LLC + SNAP LLC + SNAP