HP 200 Series Services And Applications page 92

Bridging Service
Source-Routing Bridging
There are two basic functions of the TRNSB, frame format conversion and
bridge technology conversion, as detailed below.
Frame Conversion
Frame format conversion is merely moving the fields of the Medium Access
Control (MAC) layer headers, or creating or deleting them. Figures 29 and 30
show the frame format conversions performed by the TRNSB.
SD AC FC
Figure 29. 802.5 to 802.3 Frame Conversion
Figure 29 shows how 802.5 frames are converted to and from 802.3 frames.
Since bit ordering differs between these types of networks, the bits of the
station addresses (DA, SA) must be reversed. The Routing Information Field
(RIF) is extracted when moving from 802.5 to 802.3, and inserted when
going in the other direction. (The TRNSB maintains a store of RIFs; see
below.) The 802.3 length field is also created or removed as necessary.
SD AC FC
Figure 30. 802.5 to Ethernet Frame Conversion
2-40
Routing Information
DA SA
Field (RIF)
DA SA Length
Routing Information
DA SA
Field (RIF)
DA SA 80D5
Data
Data
Data
Length Pad Data