Subject: Re: (ION) An NHC in the routed path...

From: "Albert Manfredi" <[email-masked]>
Date: Wed, 3 Mar 1999 11:33:02 -0500

-----Original Message-----
From: Navin Kumar Agarwal <[email-masked]>

>Hi All,
>
>If an NHC (with routing capability) comes in the routed path of an
NHRP
>Resolution Request packet destined for some host, what will be the
NHCs
>behaviour?
>
>Though the section 2.2 of RFC2332 specifies (as rewritten below)
that
>only NHSs should come in the path. How do we control routing table
lookup
>result in the case NHRP stations are running dynamic routing
protocols?
>
>   "If a serving NHS is to be able to supply the address resolution
>   information for an NHC then NHSs must exist at each hop along
all
>   routed paths between the NHC making the resolution request and
the
>   destination NHC."

We had a similar thread a few months ago. I think the point seems to
get missed that an NHC is _not_ expected to be a router. Or put
another way, while a router will have an NHC "module," if you will,
a router should or perhaps MUST be an NHS. (Joel Halpern suggested
that perhaps MUST is the correct word.)

Anyway, NHCs should not be in the routed path of an NHRP request or
reply. But if they are, because for some reason the router doesn't
have NHS software in it, then I would say the NHC just routes the
request or the reply. However, the NHC would not _service_ the NHRP
request. NHRP replies are generated by NHSs. That would be my
answer.

Bert
[email-masked]

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---

From: Navin Kumar Agarwal <[email-masked]>
Date: Fri, 5 Mar 1999 14:26:04 +0530 (IST)

Hi Albert,

Thanks for your prompt reply. I still have some doubts. Please go through 
my comments below.

Regards,
Navin

> that perhaps MUST is the correct word.)

	Agreed that there was a similar discussion. See below some lines 
of that discussion.

=> Mail dated Mon, 05 Oct 1998 from Diane Schuster of Lucent wrote:
=>It really boils down to how you define the functions associated with the
=>NHS and with the NHC. Is the ability to forward packets on a path other
=>than the routed path a function of the NHC or is it a function of both
=>the NHC and the NHS?

	So the discussion was on the ability to accept/initiate the 
short-cut path, not on the routing functionality in NHC/NHS.

> request. NHRP replies are generated by NHSs. 

	Yeh, here I totally agree with you.

	So shouldn't we write the reason the following MUST in the RFC2332.

	"If a serving NHS is to be able to supply the address resolution
	information for an NHC then NHSs __MUST__ exist at each hop along all
	routed paths between the NHC making the resolution request and the
	destination NHC." See section 2.2 for reference.
	
	In my opinion the reason would be as follows.

	If an NHRP resolution packet encounters any NHC along the routed 
path, and as an NHC would not help in resolving the IP address of the 
destination (Assuming that Non-authority response is also ok), it would 
be missing the chance of IP address of the destination entity getting 
resolved in midway itself (resulting in less address resolution time). 
And that is why, it is recommended that an NHRP MUST always traverse 
through the NHSs only.

	Oops, Even all these has not answered my question. Let me put
it again, if we don't want the NHRP resolution request packet to traverse
through any NHC (which is a router also) on the routed path, how do we
over-ride the result of routing table lookup?