However, when the traffic originating in the LAN is expected to terminate outside the
LAN and across the Service Provider??™s telecommunications infrastructure, this usually
means the traffic is severely throttled.
Consider a simple example, wherein some large files need to be transferred from
one enterprise office location to another across the city; let??™s assume the LANs at either
location are operating at 10M and the enterprise has subscribed to a T-1 private
line (a very reasonable scenario). This means that the LAN file traffic is subjected to
a significant (over 80 percent) reduction in speed, which is akin to traffic on a six-lane
highway suddenly having to converge into one lane; naturally, one should expect a
severe traffic-jam!47
One obvious solution to the problem of using TDM, Frame Relay, or ATM infrastructure/
services is to use higher bandwidth, but this is not a highly efficient solution. Consider
the bandwidth/speed hierarchy for SONET/TDM services that is typically available in
the access. It is a step function, similar to that shown in the Figure 1.13, with a very
inefficient profile. Let??™s assume a scenario wherein an enterprise customer who has
subscribed to 155M of bandwidth (OC-3) realizes some time later (say, 48 months)
that 500M of access bandwidth capacity is required to meet the growing needs of the
enterprise.
Pages:
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155