In frame relay the reference used to determine whether the direction of the traffic is the forward or backward direction is the frame being forwarded. The forward direction is the direction taken by the frame being forwarded.
The backward direction is the direction opposite to the direction taken by a frame being forwarded.
So if a frame is traveled from East to West, relative to this frame, the forward direction is the East-West direction and the backward direction is the West-East direction.
We added these clarifications in the new FR/PWE3 draft to be available soon.
About the processing of the different frame relay control bits (F, B, C, D) we copied almost verbatim the relevant text from ITU-T Recommendation Q.922 on frame relay data transfer protocol to avoid any misalignment.
Claude Kawa
-----Original Message-----
From: Akiva Sadovski [mailto:akiva@AXERRA.com]
Sent: Sunday, June 02, 2002 9:28 AM
To: pwe3@ietf.org
Subject: [PWE3] question regarding draft-kamapabhava-fr-pwe3-01.txt
Hi, pwe3,
In draft-kamapabhava-fr-pwe3-01:
1. the FRoPW header (control word) contains F and B bits;
2. the F-bit (FECN) definition is " FECN is copied as follows into the
FRFoPW header: If it was set to one in the incoming frame relay frame, it
must be copied unchanged in the FRoPW header. Otherwise if it was set to
zero, it may be set to zero or one, depending on the congestion state of the
PE device in the forward direction" (6.2.1)
3. it is stated in B-bit definition that the processing is as for F-bit,
but ... it's applied in backward direction.
4. now the question: what direction in PW is considered to be backward:
PSN-bound? CE-bound?
i'm sure this issue was extensively discussed on this mail list, so how can
i found any pointers ?
thanks,
Akiva
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