Re: [RPRWG] protection messages
Only partially joking, many reliable protocols run over
ethernet networks.
I agree that we need to reliably have 50 ms reaction
times to faults. It is not clear to me that sending protection
information every 10ms in non fault conditions is a good
idea.
cheers,
mike
Anoop Ghanwani wrote:
>
> Mike,
>
> CSMA/CD is non-deterministic. Anyway, I assume you were
> joking (hence the chuckle?).
>
> -Anoop
>
> > -----Original Message-----
> > From: Mike Takefman [mailto:tak@xxxxxxxxx]
> > Sent: Friday, May 24, 2002 12:47 PM
> > To: Anoop Ghanwani
> > Cc: 'Daniel Zhu'; 'Necdet Uzun'; 'stds-802-17@xxxxxxxx'
> > Subject: Re: [RPRWG] protection messages
> >
> >
> > CSMA-CD comes to mind.
> >
> > he he he,
> >
> > mike
> >
> > Anoop Ghanwani wrote:
> > >
> > > Daniel,
> > >
> > > The exponential backoff is what I don't like. I would
> > > rather see it sent at a steady rate, or just transmitted
> > > reliably so that there is no constant refresh.
> > >
> > > Are there any protocols that use a similar exponential
> > > backoff to guarantee timely delivery?
> > >
> > > -Anoop
> > >
> > > > -----Original Message-----
> > > > From: Daniel Zhu [mailto:dzhu@xxxxxxxxx]
> > > > Sent: Friday, May 24, 2002 11:19 AM
> > > > To: Anoop Ghanwani
> > > > Cc: 'Necdet Uzun'; 'stds-802-17@xxxxxxxx'
> > > > Subject: Re: [RPRWG] protection messages
> > > >
> > > >
> > > > Anoop,
> > > >
> > > > I believe, in the current RPR draft, protection message will
> > > > be broadcast periodically every 1 second in steady state.
> > > > During period of changes, protection message will be sent
> > > > much more frequently with a back off scheme up to 1 second.
> > > >
> > > > Is there something missing here?
> > > >
> > > > Daniel
> > > >
> > > > Anoop Ghanwani wrote:
> > > >
> > > > > Necdet,
> > > > >
> > > > > Thanks for pointing this out. Per the current draft,
> > > > > Type B's aren't sent that often (1/10-th the rate of
> > > > > Type A's) and so it's possible that they can be
> > > > > sourced in software.
> > > > >
> > > > > Anyway, let's assume for now that we absolutely had
> > > > > to keep protection and fairness separate. How would
> > > > > you recommend that we address the issue of timely
> > > > > delivery of the protection notification message?
> > > > >
> > > > > I see only 2 possibilties:
> > > > >
> > > > > - Periodic link status broadcasts (regardless of whether
> > > > > the link is up or not).
> > > > >
> > > > > - Hop-by-hop reliable broadcast when the link status
> > > > > changes.
> > > > >
> > > > > I'm OK with either. Can you think of any other ways
> > > > > to do this?
> > > > >
> > > > > -Anoop
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Necdet Uzun [mailto:nuzun@xxxxxxxxx]
> > > > > > Sent: Thursday, May 23, 2002 7:13 PM
> > > > > > To: Anoop Ghanwani
> > > > > > Cc: 'stds-802-17@xxxxxxxx'
> > > > > > Subject: Re: [RPRWG] protection messages
> > > > > >
> > > > > >
> > > > > > Anoop,
> > > > > >
> > > > > > Type B fairness message is generated by Fairness
> > Control Unit (in
> > > > > > hardware) and sent to client, whereas protection messages are
> > > > > > generated
> > > > > > MAC control unit (which is implemented in software) and
> > > > multicast to
> > > > > > other MACs' control units. Combining them is the worst
> > > > that can happen
> > > > > > (HW vs SW, microsecond time frame vs millisecond time
> > frame etc.)
> > > > > >
> > > > > > Thanks.
> > > > > >
> > > > > > Necdet
> > > > > >
> > > > > > Anoop Ghanwani wrote:
> > > > > >
> > > > > > > I had a comment that expressed concern about the delivery
> > > > > > > of protection notification messages.
> > > > > > >
> > > > > > > The way things are defined in D0.2, the messages are
> > > > > > > neither reliable nor periodic. There are no
> > > > > > > acknowledgments, so we are never sure that all nodes
> > > > > > > have seen the protection notification message.
> > > > > > > Sending special protection messages periodically
> > > > > > > increases the overhead (but even that is not specified).
> > > > > > > Why can't we piggyback the protection notification
> > > > > > > onto Type B fairness messages since they are required
> > > > > > > to be sent frequently in any case (typically more
> > > > > > > frequently than 1 msec)?
> > > > > > >
> > > > > > > The ad hoc's response to my comment says that Type B's
> > > > > > > are optional. This is not true. Sending of both Type A
> > > > > > > and Type B messages is mandatory per D0.2 and there have
> > > > > > > been no comments to change that behavior.
> > > > > > >
> > > > > > > -Anoop
> > > > > > > --
> > > > > > > Anoop Ghanwani - Lantern Communications - 408-521-6707
> > > > > >
> > > >
> >
> > --
> > Michael Takefman tak@xxxxxxxxx
> > Manager of Engineering, Cisco Systems
> > Chair IEEE 802.17 Stds WG
> > 2000 Innovation Dr, Ottawa, Canada, K2K 3E8
> > voice: 613-254-3399 fax: 613-254-4867
> >
--
Michael Takefman tak@xxxxxxxxx
Manager of Engineering, Cisco Systems
Chair IEEE 802.17 Stds WG
2000 Innovation Dr, Ottawa, Canada, K2K 3E8
voice: 613-254-3399 fax: 613-254-4867