Subject: Re: Locate search cleanup

From: [email-masked] (Dave Finnie)
Date: Wed, 7 Jun 95 10:01:03 EST

Roy,

Thanks for your quick response.

> A Locate(chain_flow,discard) will be sent to the child (ie,
> toward the destination CP).  This will only be done if a Locate
> chain is being maintained (i.e., a complete reply with the KEEP
> indicator set has been received).  Note that this reply may be
> received before or after the CP-SON occurs.

> When sending the Locate(chain_flow,discard), the PCID modifier/search
> number will be set to the same value that was received on the reply.
> Neither will be incremented.  If they were, then the flow would be
> seen as a new one by all DS's on downstream nodes.

> Again, a Locate(chain_flow, discard) will be sent.  It will
> use the same PCID modifier/search number that was sent on the
> Locate(complete reply, keep).

This all makes sense.

> > Also, does this cleanup logic apply on a broadcast search as
> > well as a directed search ?
>
> No, this cleanup logic only applies to a directed search where a
> Locate chain is being maintained *after* a complete reply has been
> returned to the search origin.  Such a Locate chain can only be
> maintained on a directed search.

That is kind of what is implied on 8-58 (although not specifically
stated), however, the bottom para on 8-64 states (under special cases
for search logic):

 "If a CP-CP session outage occurs along the path of a directed
  search (WITH OR WITHOUT RESERVATION), nodes on each side of the
  outage send Locate(discard) to their respective endpoints."

(The capitali{s|z}ation is mine). This seems to disagree with your
comments. Whadayareckon ?

Also, on 8-58, in the last paragraph, (I won't copy the whole thing
here,) it specifically states that Locate(discard) is generated (by
both sides of the outage) even if the Locate reply has *not* been
received. This is reinforced by the following sentence in the para:

  "If a breakage occurs in the path of a directed search after the
   Locate reply has been returned to the OCP, CPs on both sides
   of the breakage will STILL send Locate(discard) to their respective
   endpoints." (Again, capitali{s|z}ation is mine.)

This again implies that the cleanup is not only sent after a complete
reply with keep is received, but also before a reply is received at
all.

Also, just to clarify - on a broadcast search, cleanup is never done ?
So if the link between NN1 and NN2 dies, and NN1 is the parent of NN2
in a search, then NN2 simply waits for its children to reply and 
then discards knowledge of the search ?

> > Assuming answers to the above are that a rq is sent, would
> > it be normal to send only a LOCATE GDS for the cleanup flow ?
> > (ie no other GDSs in the search request.)
>
> Yes, only send a Locate GDS variable.  The Locate should contain a
> CV35 with sense code x'08900070'.

Sounds fair. Perhaps SNA Formats needs updating. On 12-25 of GA27-3136-13,
it indicates that CV35 is only present on a Locate reply.

Thanks again for your time.

Dave

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From: Dario Calia <[email-masked]>
Date: Wed, 7 Jun 95 1:10:51 PDT

Hello Roy and Dave,

A few comments from the peanut gallery :-) below...

  > comments. Whadayareckon ?

This is interesting.  What's the scoop on Locate,request,discard as
the chaser towards the NN(DLU) when we have not seen a complete_reply?

  > then discards knowledge of the search ?

Never--you would never chase a broadcast search down (just picture a
dog chasing its tail). Yup, that's one way of implementing it.

Ciao, Dario