Fragment Offset field

A common management requirement is that “all external Web traffic must flow via the organization’s Web proxy.” However, that requirement is easier stated than implemented. Discuss the various problems and issues, possible solutions, and limitations with supporting this requirement. In particular consider issues such as identifying exactly what constitutes “Web traffic” and how it may be monitored, given the large range of ports and various protocols used by Web browsers and servers.

In an IPv4 packet, the size of the payload in the first fragment, in octets, is equal to Total Length – (4  IHL). If this value is less than the required minimum (8 octets for TCP), then this fragment and the entire packet are rejected. Suggest an alternative method of achieving the same result using only the Fragment Offset field.

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