Information Technology Reference
In-Depth Information
techniques) to an IBM front-end processor (FEP), which can also have links to local Token Ring
local-area networks (LANs) and an SNA backbone. The two sites are connected through an SDLC-based
56-kbps leased line.
Figure10-2 A Typical SDLC-Based Network Configuration
Local site
IBM mainframe
Front-end processor
SDLC Link
Establishment
controller
Token
Ring
Terminals
Remote site
SRB
The SRB algorithm was developed by IBM and proposed to the IEEE 802.5 committee as the means to
bridge among all LANs. The IEEE 802.5 committee subsequently adopted SRB into the IEEE 802.5
Token Ring LAN specification.
Since its initial proposal, IBM has offered a new bridging standard to the IEEE 802 committee: the
source-route transparent (SRT) bridging solution. SRT bridging eliminates pure SRBs entirely,
proposing that the two types of LAN bridges be transparent bridges and SRT bridges. Although SRT
bridging has support, SRBs are still widely deployed.
SRB Algorithm
SRBs are so named because they assume that the complete source-to-destination route is placed in all
inter-LAN frames sent by the source. SRBs store and forward the frames as indicated by the route
appearing in the appropriate frame field. Figure 10-3 illustrates a sample SRB network.
