RE: [RPRWG] More comments on preemption
- we are talking about an "Escape" code maybe once every 256 bytes. This
shouldn't impact clock recovery but I agree we should qualify this.
- are you implying we should have a glueless interface between the RPR ring and
a customer Ethernet interface? From your comments, this is the feeling I get.
My personal guess is that we will require glue (inter-working) between the RPR
MAC and the drop side (customer interface). I also thought that we weren't
discussing this inter-working function in RPR. We are defining an RPR MAC.
- PHYs can be constructed with a "bypass 8B/10B" interface or else.
jld.
marconi networks.
"Devendra Tripathi" <tripathi@xxxxxxxxxxxx> on 05/03/2001 09:17:36 PM
To: Jeanlou Dupont/MAIN/MC1@MCMAIN
cc: "William Dai" <wdai@xxxxxxxxxxxx>, stds-802-17@xxxxxxxx
Subject: RE: [RPRWG] More comments on preemption
Hi William,
Actually, it is not just a question of symbol. The PCS layer of 1/10 G
Ethernet
PHY makes quite a few assumtions on where an IDLE can come. IDLE is also
used to decide on clock compensation. In all likelyhood such a packet will
be declared erroneous ( I need to look this more seriously to be
conclusive).
If we decide to use the reserve symbol to mark Escape, there may be
compatibility (of PHY devices) issues.
The other issue is related to frame format change at gateway (LAN/MAN)
points.
The default understanding which I had was that when a Packet from LAN comes
to
Metro area, it requires add/delete of header and that is about it (as
for as frame format is concerned). But this may not be strong issue though.
Regards,
Devendra Tripathi
VidyaWeb Inc.
Pune, India
Tel: +91-20-433-1362
> -----Original Message-----
> From: jeanlou.dupont@xxxxxxxxxxx [mailto:jeanlou.dupont@xxxxxxxxxxx]
> Sent: Friday, May 04, 2001 4:53 AM
> To: Devendra Tripathi
> Cc: William Dai; stds-802-17@xxxxxxxx
> Subject: RE: [RPRWG] More comments on preemption
>
>
>
>
>
> Could you clarify your statement "... definitely takes us away
> from Ethernet"?
>
> If you are targeting your comment at the Ethernet PHY layer: the
> Ethernet (100
> & 1000) uses 8B/10B encoding.
> There are some "spare symbols" not used (if I am not mistaken)
> that could be
> redefined to mean "IDLE/Escape".
>
> Jean-Lou Dupont
> Marconi Networks.
>
>
>
>
>
>
> To: "William Dai" <wdai@xxxxxxxxxxxx>, stds-802-17@xxxxxxxx
> cc: (bcc: Jeanlou Dupont/MAIN/MC1)
>
> Subject: RE: [RPRWG] More comments on preemption
>
>
>
>
>
> > 3. Each M and L packet transfer will be inserted an "IDLE/Escape"
> > word for every 256 byte (for the sake of alignment/padding concern)
> > as the preemptive insertion point.
>
> This is very good idea to manage pre-emption and other QOS related
> considerations but this definitely takes us away from Ethernet.
>
> Regards,
> Devendra Tripathi
> VidyaWeb Inc
>
>
>
>
>
>