RE: Fw: [RPRWG] CRC check in each node?
Pankaj/Angela/Bob,
I have a question: where is this bit located - in the header, protected by
the header's CRC or in the payload, protected by payload's CRC?
Igor
-----Original Message-----
From: owner-stds-802-17@xxxxxxxxxxxxxxxxxx
[mailto:owner-stds-802-17@xxxxxxxxxxxxxxxxxx]On Behalf Of Pankaj K Jha
Sent: Monday, July 02, 2001 12:40 PM
To: afaber@xxxxxxxxxxxxx
Cc: ieee 802.17 list
Subject: Re: Fw: [RPRWG] CRC check in each node?
Angela/Bob:
Yes it does. I'm ok with the following summary:
- If there is an error in RPR header, the node discards the packet (since it
doesn't know for sure who the destination node is), and updates its
statistics.
- Same is true if both RPR header and payload CRC are bad
- If RPR header is ok but the payload CRC is bad, the node optionally (under
program control) sets a bit, and updates its own statistics, and sends the
packet downstream. This is done so the end node can tell the link is not
functioning properly rather than assume the link is fine but no one is
transmitting packets to it.
Any thoughts?
-Pankaj
afaber@xxxxxxxxxxxxx wrote:
> hello Pankaj
>
> Since CRC can be used for identifying if there is a problem in the link
> (i.e., signal degradation causing the CRC error), it is desirable to only
> record this data in the first node that sees this CRC error (so that one
> can see that there may be a fault in the link). If every node that sees
the
> same CRC error accumulate such data, how are you going to identify which
> one is the link that generated the error? The bit set is used (as I heard
> from the 802.5 folks) to say that the CRC error was already detected
> upstream and there is no need to use that information on performance
> monitoring of downstream nodes...
>
> Does it make sense?
>
> Angela
>
> Pankaj K Jha <pkj@xxxxxxxxxxx> on 07/02/2001 11:42:04 AM
>
> To: RDLove <rdlove@xxxxxxxxx>
> cc: "Angela T. Faber" <afaber@xxxxxxxxxxxxx>, "ieee 802.17 list"
> <stds-802-17@xxxxxxxx> (bcc: Angela T. Faber/Telcordia)
> Subject: Re: Fw: [RPRWG] CRC check in each node?
>
> I've one doubt I'd like to clarify. If it is only for the local station to
> record statistics, why would it have to set a bit in the packet to do so?
> It
> already knows there is a CRC error and it can update its statistics
> locally. As
> far as other other downstream nodes are concerned, they too will find the
> CRC
> errors during reception because they'll be checking for CRC errors anyway.
> What
> exactly does the bit setting help in? It doesn't help in node
> identification in
> a series of nodes. Please advise.
> Regards,.
> Pankaj
>
> RDLove wrote:
>
> > Pankaj, the reason to set a bit when a station sees a CRC error, is so
> that
> > the station that first sees the error can record the "error created"
> event.
> > It is that station, and not the destination station with the information
> > available for transmitting to a station that gathers statistics.
> >
> > Best regards,
> >
> > Robert D. Love
> > Chair, Resilient Packet Ring Alliance
> > President, LAN Connect Consultants
> > 7105 Leveret Circle Raleigh, NC 27615
> > Phone: 919 848-6773 Mobile: 919 810-7816
> > email: rdlove@xxxxxxxx Fax: 208 978-1187