CS 573 : Autumn 2004 - 2005 Handout # 10 a

A. [3pts] For transparent bridges complying with the IEEE 802.1D standard, it is proposed that the “age field” parameter be kept internal to the bridge instead of transmitting it in the BPDU. That is, the bridges will time out on a configuration message by keeping an “internal” timer for the age field. This will result in a reduction in BPDU size which will, in turn, save the bandwidth. Do you support the proposition? Why? Why not? We do not support the proposition. Consider a new bridge, which will not be the root, comes up in an active topology. This new bridge must be informed by the neighboring bridges about the root, cost to root, etc. The neighboring bridges must also tell the new bridge about the freshness of this information, which is precisely done by including the age field in the BPDU itself. If the age field is not included, the new bridge (and the part of network served by that bridge) might take unnecessarily long time to detect subsequent root bridge failures.