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276 Chapter 9: Frame Relay Connection Controlling Traffic Flow
Foundation Summary
Frame Relay is a highly versatile technology. It supports data in varying degrees and speeds,
and it supports voice traffic. In addition, it can tell the difference between the two traffic types.
At this point, your understanding of Frame Relay is slightly better than it was when you began
the chapter. For the exam, however, you must thoroughly understand the operation of Frame
Relay technology. Thus, it would be worth the time involved to go back and read the chapter
again to make sure the finer points of traffic parameter manipulation have been cemented in.
Table 9-3 shows a review of the Frame Relay LMI types supported by Cisco routers.
Table 9-4 provides review information regarding Frame Relay topologies.
Table 9-5 revisits the topic of Frame Relay traffic shaping. This table is a near duplicate of
Table 9-2 and is placed here for review purposes.
Table 9-3
LMI Types
LMI Type
Also Known As
Defined by
Cisco
Gang of Four
Cisco, StrataCom, NortTel, and DEC
ANSI
Annex D
T1.617 Annex D
Q933a
Annex A
Q.933 Annex A
Table 9-4
Frame Relay Topologies
Topology
Description
Hub and Spoke
(a.k.a. Star)
This is the dominant method of deploying Frame Relay. It consists of a single
central site acting as a connection point for all remote offices. Routing between two
satellite offices is accomplished through the central site. This tends to be the lowest
cost solution; however, it is also the least redundant (that is, fault tolerant) strategy.
Full Mesh
This topology consists of a large number of connections. It is very expensive to
operate; however, it is the most fault tolerant. Because each site is connected to
every other site, the number of connections can quickly grow and become
expensive. The formula for deriving the number of required connections is
n(n ­ 1)
ч 2, where n is the number of devices you wish to connect.
Partial Mesh
This implementation is hub and spoke with redundancy. The cost of full mesh is
avoided and the lack of fault tolerance of hub and spoke is minimized. A central site
is still utilized; however, redundant connections are installed between critical sites.
In essence, it is possible to create a backup central site. This is particularly useful in
networks in which delay reductions are necessary because the capability to get to a
destination without traversing a central router decreases delay significantly.