HP 600 Series, Services And Applications

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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.
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.
Figure 30. 802.5 to Ethernet Frame Conversion
SD AC FC
DA SA
Routing Information
Field (RIF)
Data
SA DA Length Data
80D5 Pad SA DA Length Data
SD AC
FC DA SA
Routing Information
Field (RIF)
Data
Bridging Service
Source-Routing Bridging
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