Subject: [pim] Bootstrap messages and Fragment Tag

From: Pavlin Radoslavov <[email-masked]>
Date: Thu, 13 Feb 2003 15:03:34 -0800

A question for all PIM-SM implementors.

The definition of the Fragment Tag in the Bootstrap message is:

Fragment Tag
     A randomly generated number, acts to distinguish the fragments
     belonging to different Bootstrap messages; fragments belonging to
     same Bootstrap message carry the same `Fragment Tag'.

So far my understanding was that whenever the BS Timer at the BSR
expires and the BSR resends the BSM, then this is a new/different
Bootstrap message (even though the Cand-RP set hasn't changed),
therefore the BSR uses a different Fragment Tag.
E.g., the simplest solution is for the BSR to start with a
randomly-generated Fragment Tag, and then increment it whenever it
has to send another BSM.

However, on another fresh reading of the draft I became a little bit
dubious about what the definition of "different Bootstrap message"
is. I.e., if someone assumes that "different" means only if the
content of the message has changed, then this means that the BSR
will be resending periodically BSMs with the same Fragment Tag.

I'd like to know whether there are BSR implementations that keep
reusing the same Fragment Tag if the BSM content hasn't changed.
Or, am I the only one who thinks that the Fragment Tag should be
changing?

Thanks,
Pavlin
_______________________________________________
pim mailing list
[email-masked]
http://catarina.usc.edu/mailman/listinfo/pim

---

From: [email-masked]
Date: Thu, 13 Feb 2003 16:05:13 -0800 (PST)

Hi Pavlin,

How are you?  I've always assumed the fragment tag was unique to a set
of fragments from one advertisement from the BSR, this to allow
recieving routers to re-assemble fragments. Otherwise, if it is unique
to a set across advertisements, then how would you know which
advertisement a particular fragment belonged to.

Note that i can't imagine having enough C-RPs to require a fragmented
BSR message, nor why a fragment from one advertisement would still be
zinging around a network after an entire period has passed.  But
that's how i've always interpreted the fragtag.

I personally have never written an implementation that uses the same
fragment tag ;)

-rusty

---

From: Mark Handley <[email-masked]>
Date: Thu, 13 Feb 2003 16:15:58 -0800

>I personally have never written an implementation that uses the same

Rusty,

The use of multiple fragments is required if you support admin scoping.

 - Mark

---

From: [email-masked]
Date: Thu, 13 Feb 2003 16:24:32 -0800 (PST)

> The use of multiple fragments is required if you support admin scoping.

Ok sure, that makes sense.

thanks,

- rusty