Re: [RPRWG] Frame reorder in 802.17b
Well, sort of correct. I remember that we removed the statements that forbade wrapping from using bidirectional flooding. But looking at Table 7.29, Row 29, I see that although the choice for an individual frame is allowed to be bidirectional in a both steering and wrapping systems, the default value of bidirectional is not allowed. This doesn't make much sense (to me) and is something that should probably be corrected during maintenance.
jl
-----Original Message-----
From: owner-stds-802-17@listserv.ieee.org
[mailto:owner-stds-802-17@listserv.ieee.org]On Behalf Of Steven Wood
(swood)
Sent: Tuesday, November 16, 2004 7:33 PM
To: STDS-802-17@listserv.ieee.org
Subject: Re: [RPRWG] Frame reorder in 802.17b
I believe that the use of bi-directional flooding is not
precluded for wrapping rings. Thus, that would be one
possible solution.
> -----Original Message-----
> From: owner-stds-802-17@listserv.ieee.org
> [mailto:owner-stds-802-17@listserv.ieee.org] On Behalf Of
> Leon Bruckman
> Sent: Tuesday, November 16, 2004 6:56 PM
> To: STDS-802-17@listserv.ieee.org
> Subject: [RPRWG] Frame reorder in 802.17b
>
> Assume the following ring: S1-S2-S3-.....-S64
>
> S1 is transmitting a frame with user DA=A, and the user with
> MAC=A is connected to S64. S1 does not have an entry in the
> SAS DB for A, so it floods it (assume unidirectional flood)
> through ringlet0 (S2, S3, ....
> S64).
> Eventually S64 receives the frame and it reaches user A. User
> A responds, and S64 forwards the frame to S1.
>
> - If we optimize the path by using minimum hops as the direct
> path: S64 sends the frame to S1 directly through ringlet0,
> and the next frame from
> S1 to A will use ringlet1 with a direct frame since it has
> already learned that A is represented by S64. Reorder will
> result since old frames from S1 to A may be in flight in the
> long ringlet0 flooded path.
>
> - A trivial solution would be for S1 to continue using
> ringlet0 with direct frames. This is suboptimal since S1 uses
> the longest path.
>
> - Using bidirectional flooding, with the right cleave point
> solves the problem, but in wrapping rings unidirectional
> flood is used, and even for steering rings unidirectional
> flooding is simpler (no duplication).
>
> Comments please.
>
> Leon
>