Consider a virtualcircuit network Suppose that VC number is

Consider a virtual-circuit network. Suppose that VC number is an 8-bit field. a. What is the maximum number of virtual circuits that can be carried over a link? b. Suppose a central node determines paths and VC numbers at connection setup. Suppose the same VC number is used on each link along the VC’s path. Describe how the central node might determine the VC number at connection setup. Is it possible that there are fewer VCs in progress than the maximum as determined in part (a) yet there is no common free VC number? c. Suppose that different VC numbers are permitted in each link along a VC’s path. During connection setup, after an end-to-end path is determined, describe how the links can choose their VC numbers and configure their forwarding tables in a decentralized manner, without reliance on a central node.

Solution

a.
The maximum number is 2pow8=256
b.
The centralized node can use any number from 0~255 which is not be used now. It’simpossible that fewer VCs in progress than 256, if there is no common free VC number.
c.
Each link can allocate a VC number from 0~255. For each link, it shouldn’t has the same VC number as any other link in this path. Router in the VC path must replace the VC number of each incoming packet to the certain outbound link VC number