Subject: (ION) what's the difference between ERR_L_DROP, ERR_L_RELEASE

From: [email-masked] (wanghai)
Date: Thu, 11 Jun 1998 09:54:46 +0800

Mr Armitage:
 Sorry this question comes late. 
 I review the RFC 2022 again when after the reading of IEEE paper of
your's . a question arose here: what's the difference between ERR_L_DROP
,ERR_L_RELEASE?
 in my understanding, ERR_L_DROP refer to a leaf drop at ATM layer. So
the p-mp VC still alive,but lost a leaf.
 ERR_L_RELEASE refer to a VC broken at ATM layer. So the P_MP VC are
stopped immediately.
 am I right?  
 if then, when MARS receive a ERR_L_RELEASE on CLUSTERCONTROLVC, that
means ClustercontrolVC are dead at that time, so some action must be
taken instead of just discard a leaf on ClustercontrolVC.
  from the algorithm for ERR_L_RELEASE, I found it is much proper for
MARS receive ERR_L_DROP, that means a leaf was dead, but
ClustercontrolVC still alive. 
  there is no action for MARS receiving ERR_L_DROP, it did not receive
such message at all? why?
   I think this problem is too big to be ignored. So there must be
something I am wrong. Can you point it out for me?

                                               Hai Wang
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---

From: Grenville Armitage <[email-masked]>
Date: Wed, 08 Jul 1998 22:50:22 -0400

Hai,

>  Sorry this question comes late.

that's okay. sorry my reply came late too :)

>  ERR_L_RELEASE refer to a VC broken at ATM layer. So the P_MP VC are

Yes. ERR_L_DROP was supposed to be a subset of ERR_L_RELEASE.
In general ERR_L_RELEASE on a pt-mpt VC would indicate that
_all_ leaf nodes had dropped off (or the VC had been torn down
through some other event)

> something I am wrong. Can you point it out for me?

No, actually, you are right. The text in RFC2022 around section 6.1.2
appears to have collapsed the ERR_L_DROP and ERR_L_RELEASE responses
together. Strictly speaking the last paragraph of 6.1.2 refers to
the actions taken by the MARS when it receives an ERR_L_DROP
(and indication that an individual leaf node has dropped). Receipt
of an ERR_L_RELEASE case implies all leaf nodes have been dropped
(functionally equivalent to receiving an ERR_L_DROP from each cluster
member, so the MARS would remove _all_ cluster members from its
internal database)

(In practical ATM signaling systems the functional equivalent of
ERR_L_DROP indication is a special version of ERR_L_RELEASE, which
is why no-one has noticed this before, I suspect)

cheers,
gja
________________________________________________________________________
Grenville Armitage                          High Speed Networks Research
http://nj5.injersey.com/~gja              Bell Labs, Lucent Technologies