obviously very important, but optimizing the bandwidth on a WAN can be
very difficult. The best way to reduce the bandwidth usage is to reduce the
amount of update traffic on the LAN that will be sent over your WAN. The
Cisco IOS features available to help reduce bandwidth usage are as follows:
or exiting a specific router interface. They can stop basic traffic, broad-
casts, and protocol updates from saturating a particular link. TCP/IP,
IPX, and AppleTalk can all be filtered extensively.
distance-vector protocols, it allows routers to exchange full distance-
vector routing information at an interval defined by the administrator.
data compression to reduce the amount of traffic crossing a WAN link.
Link compression can be configured, which compresses header and data
information into packets. This is accomplished by the Cisco IOS prior to
sending the frame across the WAN.
used selectively. With it, the administrator can define "interesting" traffic
on the router and initiate point-to-point WAN links based upon that traf-
fic. What denotes interesting traffic is defined by access lists, so a great
deal of flexibility is afforded to the administrator. For instance, an expen-
sive ISDN connection to the Internet could be initiated to retrieve e-mail,
but not for a WWW request. DDR is an effective tool in situations where
WAN access is charged according to a quantified time interval--it's best
to use it in situations where WAN access is infrequent.
incremental updates, you can reduce the number of router processing
cycles by reducing the entries in a routing table. Route summarization
occurs at major network boundaries, which summarize all the routes
advertised into one entry. Incremental updates save bandwidth by sending
only topology changes instead of the entire routing table when transmit-
ting updates.
Relay provide global connectivity through a large number of service pro-
viders with established circuits to most major cities.