RE: [RPRWG] More comments on preemption
Hi Raman,
>From my Ethernet background, the control symbols are differentiated only
by PCS layer (or a small sub layer of MAC marked as re-conciliation layer).
This is because in Ethernet there is no concept of extensive header per
packet. Since RPR MAC is expected to operate with Ethernet PHYs, it is
important to consider the implications there. Could you clarify how ESC will
be
embedded by POS ?
Regards,
Devendra Tripathi
VidyaWeb Inc.
Pune, India
Tel: +91-20-433-1362
> -----Original Message-----
> From: Raman Venkataraman [mailto:kvraman@xxxxxxxxxxxxxxxx]
> Sent: Friday, May 04, 2001 7:14 AM
> To: Devendra Tripathi; jeanlou.dupont@xxxxxxxxxxx
> Cc: William Dai; stds-802-17@xxxxxxxx
> Subject: Re: [RPRWG] More comments on preemption
>
>
> Hi,
> My understanding of William's proposal for the IDLE/Escape marking is
> in the 802.17 MAC level and it is not clear to me why PCS layer is getting
> involved.
> It looks to me that if we use the POS transport, the special ESC sequence
> can be
> used for detecting the special markings. However, if we use the
> GFP for the
> transport,
> the escape sequences will be stripped before encapsulating the
> packets into
> the GFP.
> So, it looks like this method will work if we use the POS.
> Regards
> Raman
> ----- Original Message -----
> From: Devendra Tripathi <tripathi@xxxxxxxxxxxx>
> To: <jeanlou.dupont@xxxxxxxxxxx>
> Cc: William Dai <wdai@xxxxxxxxxxxx>; <stds-802-17@xxxxxxxx>
> Sent: Thursday, May 03, 2001 6:17 PM
> 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
> > >
> > >
> > >
> > >
> > >
> > >
> >
>
>