RE: [rohc] TCP/IP EPIC profile

["Per Synnergren (EPL)" <[e-mail]>]

Hi all, 
 
A question "out of the blue"...
 
Hongbin Liao wrote:

1. whether can TCP/IP EPIC profile correctly describe the behavior of TCP? Or, whether EPIC is powerful enough to describe the complicated behavior of TCP/IP?

    In EPIC, fields are assumed to be independent from each other. Once each field's behaviors are described well, the whole protocol's behaviors are also well-studied. However, in practice, fields in a protocol may not behave independently completely from each other. There may be some connections (or causality) among several fields. For example, most TCP traffics only contain one-way traffic (WWW browsing, FTP downloading, etc.), i.e., only SEQ changes on the forward path (from server to client) and only ACK changes on the backward path (from client to server). The ACK on the forward path and SEQ on the backward path remain constant. However, in TCP/IP EPIC profile, the probabilities for SEQ and ACK are specified seperately:



It is obvious that knowledge about "TCP inter-field correlation" could be useful in order to increase the performance of the header compression. Has anyone heard of/or performed thorough studies of the cross-correlation between TCP-fields?