RE: [RPRWG] control TTL (the 255-station and 2000-km issue)
Mike,
Relative to documenting proposals and the
following:
>>That is a fair request David, and I will do
>>my best to accomdate it.
I look forward to that time, whereupon
data (as opposed to email perserverse) will
conquer.
>>Don't get me wrong, I do like your slick trick,
>>but your solution is to change the frame format
>>and add new features, whereas I am working to
>>fix the currently approved text.
I believe all bridge proposals have some format
change required. Shouldn't matter, since it better
to force the encoding to provide the desired
functionality, rather than force-fit the
functionality to the pre-ordained encoding(:>).
DVJ
David V. James, PhD
Chief Architect
Network Processing Solutions
Data Communications Division
Cypress Semiconductor, Bldg #3
3901 North First Street
San Jose, CA 95134-1599
Work: +1.408.545.7560
Cell: +1.650.954.6906
Fax: +1.408.456.1962
Work: djz@xxxxxxxxxxx
Base: dvj@xxxxxxxxxxxx
>>-----Original Message-----
>>From: owner-stds-802-17@xxxxxxxxxxxxxxxxxx
>>[mailto:owner-stds-802-17@xxxxxxxxxxxxxxxxxx]On Behalf Of Mike Takefman
>>Sent: Monday, June 24, 2002 8:17 PM
>>To: djz@xxxxxxxxxxx
>>Cc: Anoop Ghanwani; stds-802-17@xxxxxxxx
>>Subject: Re: [RPRWG] control TTL (the 255-station and 2000-km issue)
>>
>>
>>
>>That is a fair request David, and I will do
>>my best to accomdate it.
>>
>>Consider instead a host on your ring. Are you
>>suggesting that hosts have to behave as
>>bridges do in terms of learning the mappings
>>of MAC addresses to bridge IDs?
>>
>>If so, I believe you are placing an overly
>>large burden on hosts, one that no other 802
>>standard has done.
>>
>>Either way, the scenario I pointed out for bridges
>>(that you deflected by pointing out that I was
>>assuming a different scenario (which is fair
>>on your part)) is back. A bridge flooding a non local
>>packet for the first time, a host inserting a packet
>>that is off ring, but does not know which bridge
>>it exits (which in my world happens for every host
>>packet). If that station goes off the ring, ttl
>>will be the only mechanism to stop the double
>>delivery.
>>
>>Don't get me wrong, I do like your slick trick,
>>but your solution is to change the frame format
>>and add new features, whereas I am working to
>>fix the currently approved text.
>>
>>cheers,
>>
>>mike
>>
>>
>>
>>David James wrote:
>>>
>>> Mike,
>>>
>>> I believe part of the problem is that you claiming
>>> something that is not documented does not fail.
>>> Its hard to argue, as the definition can change
>>> whenever a failure is illustrated.
>>>
>>> Perhaps you should document the TTL stripping
>>> protocols with some background text and illustrations?
>>> And, clearly define the synchronizatoin points
>>> with Discovery, that are often implied.
>>>
>>> In my comments to D0.3 I have done this for DSID scoping.
>>> While this was much easier (since it doesn't have
>>> all of TTL stripping exceptions and problems), I believe
>>> its only fair to ask for you to do the same.
>>>
>>> Then, we will be able to analysize a problem,
>>> without the problem statement constantly changing.
>>>
>>> Even after that, there is the basic problem that:
>>> 1) Bidirectional flooding is required for performance.
>>> 2) A single-stations failure of (1) generates a duplicate
>>> 3) An multi-station failure of DSID stripping
>>> generates no duplicates.
>>>
>>> Remember, 2/3 is the failure scenario you mentioned
>>> in previous email. Having agreed, I'm a bit surprized
>>> this no longer appears to be a concern to you, just
>>> because the repercussions of that statement changed...
>>>
>>> DVJ
>>>
>>> David V. James, PhD
>>> Chief Architect
>>> Network Processing Solutions
>>> Data Communications Division
>>> Cypress Semiconductor, Bldg #3
>>> 3901 North First Street
>>> San Jose, CA 95134-1599
>>> Work: +1.408.545.7560
>>> Cell: +1.650.954.6906
>>> Fax: +1.408.456.1962
>>> Work: djz@xxxxxxxxxxx
>>> Base: dvj@xxxxxxxxxxxx
>>>
>>> > -----Original Message-----
>>> > From: owner-stds-802-17@xxxxxxxxxxxxxxxxxx
>>> > [mailto:owner-stds-802-17@xxxxxxxxxxxxxxxxxx]On Behalf Of
>>Mike Takefman
>>> > Sent: Monday, June 24, 2002 1:31 PM
>>> > To: Anoop Ghanwani
>>> > Cc: 'djz@xxxxxxxxxxx '; 'stds-802-17@xxxxxxxx '
>>> > Subject: Re: [RPRWG] control TTL (the 255-station and 2000-km issue)
>>> >
>>> >
>>> >
>>> > Anoop,
>>> >
>>> > For a protection hierarchy to work all nodes
>>> > need to know about all failures.
>>> >
>>> > I agree with your comment that this needs to be
>>> > clearly documented as part of the standard.
>>> > Futhermore, if the WG decides to accept this
>>> > TTL decrement algorithm it must be documented
>>> > properly.
>>> >
>>> > With regard to your last question / comment.
>>> > In wrapping, the adjacent nodes can react immediately if
>>> > they have the highest priority failure. Thereby
>>> > wrapping will have quicker reaction times to
>>> > steering. The need to broadcast in the wrapping
>>> > case is to support the hierarchy. If no hierarchy
>>> > was supported, then the decision could be completely
>>> > local. In this case I would still argue that a
>>> > broadcast of the event was useful for 2 reasons.
>>> > 1) The same algorithm supports steering which is
>>> > the default mode
>>> > 2) The packets that are trapped on the wrong ring
>>> > will get killed.
>>> >
>>> > cheers,
>>> >
>>> > mike
>>> >
>>> >
>>> > Anoop Ghanwani wrote:
>>> > >
>>> > >
>>> > > Mike,
>>> > >
>>> > > I was trying to say that when a node "unwraps" due
>>> > > to the ring healing, it can't throw away packets
>>> > > forever because the ring might wrap at some other
>>> > > place making it valid for this node to see packets
>>> > > with the wrap bit set. Therefore a node would have
>>> > > to set some kind of timer (on the order of RTT) and
>>> > > only throw away packets for that duration.
>>> > >
>>> > > The above discussion was trying to solve the problem
>>> > > where all nodes do not know about protection events;
>>> > > only those adjacent to the fault do. If all nodes do
>>> > > know about protection events, the solution you mention
>>> > > should work, but it does need to be documented in the
>>> > > spec.
>>> > >
>>> > > [Off topic discussion]
>>> > > To me, it seemed like the main argument for doing wrapping
>>> > > is that only nodes adjacent to the fault need to know about
>>> > > it and react to it. If all nodes do need to know about
>>> > > a protection event, then it it probably more efficient
>>> > > for them to use steering.
>>> > >
>>> > > -Anoop
>>> > >
>>> > > -----Original Message-----
>>> > > From: Mike Takefman
>>> > > To: Anoop Ghanwani
>>> > > Cc: djz@xxxxxxxxxxx; stds-802-17@xxxxxxxx
>>> > > Sent: 6/24/02 12:07 AM
>>> > > Subject: Re: [RPRWG] control TTL (the 255-station and 2000-km issue)
>>> > >
>>> > > Anoop,
>>> > >
>>> > > wrapping nodes always communicate with every other
>>> > > node anyway. This is necessary for protection
>>> > > heirarchy to work. Also, given the broadcast
>>> > > nature of messages to make steering work in under
>>> > > 50 ms, I have no concern over all nodes knowing
>>> > > that all protection events are done and the ringlets
>>> > > are healed.
>>> > >
>>> > > If one waits for the ringlets to be healed
>>> > > and then killing the packet life is fine. Or
>>> > > maybe I did not understand your comment.
>>> > >
>>> > > mike
>>> > >
>>> > > Anoop Ghanwani wrote:
>>> > > >
>>> > > > > > The problem with (3), which you seem to advocate,
>>> > > > > > is the time gap between the wrap action and the
>>> > > > > > the distribution/settling of the wrap state information
>>> > > > > > in other stations. During this time difference, any
>>> > > > > > and all TTL-strip based frames will be discarded.
>>> > > > >
>>> > > > > A good point david, in response please consider the following
>>> > > > >
>>> > > > > Never decrement when on the wrong ring. Once the wrap
>>> > > > > state is left, kill the packet if the ring id
>>> > > > > is wrong. THus going into wrap does not cause the
>>> > > > > packets to be prematurely lost. When leaving wrap
>>> > > > > the packets will be killed once everyone knows
>>> > > > > the wrap is over.
>>> > > >
>>> > > > Mike,
>>> > > >
>>> > > > Does everyone on the ring know when a wrap has occured
>>> > > > and when it heals? I thought wrapping was a local issue
>>> > > > and only nodes adjacent to the fault know about it.
>>> > > > In that case, if the node at which wrapping occurs
>>> > > > detects a heal, and for some reason doesn't pull a wrap
>>> > > > packet off, it will continue to circulate forever.
>>> > > > The node can't be dropping wrapped packets forever
>>> > > > because the wrap could occur somewhere else at
>>> > > > which time it would be a legal packet for pass-through.
>>> > > >
>>> > > > -Anoop
>>> > >
>>> > > --
>>> > > 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
>>> >
>>
>>--
>>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