Subject: Re: M2PA: link changeover and associations

From: Tom George <[email-masked]>
Date: Thu, 18 Oct 2001 08:42:50 -0500

Howard,

Questions 1 and 2 are really about MTP3, not M2PA. So rather than try to
explain it myself, I will refer you to Q.704 section 5 (or the ANSI
equivalent).

3: M2PA allows for the multiple associations between IP addresses. The
case I can think of where this might be useful is if you are making a
converter box with several incoming traditional SS7 links and one
outgoing IP connection. You might want to have a virtual IP link for
each incoming traditional link. 

In the case of having IP links between SPs, I doubt that we would ever
have multiple associations between IP addresses.

tomG.

Howard Lew wrote:
> 
> Hello,
> 
> I have several questions about M2PA's description of changeover and
> associations in draft-ietf-sigtran-m2pa-03.txt.
> 
> 1) In 5.8 Link Changeover, when an association breaks each M2PA layer on
> each side will report Out of Service to MTP3 right?  How is it
> determined that which side sends the XCO and which side will just wait
> and reply with an XCA.
> 
> 2) Does the XCO that is supposed to go on "another link" refer to an
> association to a signaling point C if the association between signaling
> points A and B break?  If this is the case, then I would assume that the
> signaling point C sits somewhere in between and forwards the XCO and XCA
> messages right?
> 
> Or must that "another link" refer to a second link between signaling
> points A and B (i.e. signaling points A and B have 2 associations
> connecting each other)?
> 
> 3) Is Figure 10 just an example to illustrate that multiple associations
> can be created between 2 IP addresses?  Is there really any benefit to
> creating multiple associations between the same IP addresses?
> 
> Thanks in advance for any information.
> Howard
> 
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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Fri, 19 Oct 2001 15:38:21 -0500

Howard,

Please see comments below...

Tom George wrote:                                             (Thu, 18 Oct 2001 08:42:50)
> > determined that which side sends the XCO and which side will just wait

In SS7 both sides send XCO and await XCA.  Each side must receive XCA
to perform buffer updating on its side.

> > signaling point C sits somewhere in between and forwards the XCO and XCA

For links down between signalling point A and B, the XCO takes any
normal available path between A and B in each direction.

> > points A and B (i.e. signaling points A and B have 2 associations

There are some good diagrams in section 5 that Tom cited above.

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Brian F. G. Bidulock
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