Subject: Re: (ION) RFC 2332 again

From: "Albert Manfredi" <[email-masked]>
Date: Mon, 9 Nov 1998 14:36:10 -0500

Archana,

As I read it, that paragraph is saying that the NHS must reply with
all of the authoritative CIEs that match the NHC's request. But what
does that mean? It means (I think) only that the requesting NHC
asked for resolution without knowing what the extent of prefix
length could be.

An NHC isn't expected to know that, right? Not at first. So it might
ask for 1.2.3.4/16 without knowing that the actual entry should be
1.2.3.4/24. So the NHS replies to that request with 1.2.3.4/24 and
1.2.4.1/24, let's say.

Now the NHC only has one good choice.

Bert
[email-masked]

-----Original Message-----
From: Archana Nehru <[email-masked]>
Date: Monday, November 09, 1998 2:26 PM
Subject: Re: (ION) RFC 2332 again

>Albert Manfredi wrote:
>>
>> My answer would be that _if_ an NHS serving 1.2.4.5/24 is
available,
>> _then_ no other NHS could be responding with 1.2.3.4/16 ever.
>> Because the only way for any NHS to respond with 1.2.x.x/16 is if
>> this NHS is the egress point for _all_ 1.2.x.x subnetworks beyond
>> the ATM backbone.
>>
>
>Bert,
>I am not talking about two different NHSs but only one NHS. I am
just
>wondering if it is possible that two overlapping registrations are
>possible?. As per my understanding .overlapping registrations by
NHCs
>seem to be allowed. Refer to section 5.2.2 of RFC 2332 which says"
for a
>resolution request reply ALL the CIEs in the next hop cache that
match
>the query"..if overlapping registrations are not allowed, then what
does
>"all" mean in the above?
>
>-regards
>Archana
>
>___________________________________________________________________
_____
>Archana Nehru                     :  Trillium Digital Systems, Inc
>E-mail: [email-masked]       :  Los Angeles, California
>Phone: +1 310 442 9222
>___________________________________________________________________
_____

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From: Archana Nehru <[email-masked]>
Date: Mon, 09 Nov 1998 12:37:27 -0800

Hi,
Please see my comments below:

Albert Manfredi wrote:
> length could be. An NHC isn't expected to know that, right? Not at first.

True, an NHC might just start with 1.2.3.4/16, so all the entries that
match 1.2.*.* will be returned.

So it might
> Now the NHC only has one good choice.

I am not sure why you are saying that an NHS will return the 1.2.3.4/24
to the ingress NHC when the only match it finds in its registered cache
is 1.2.3.4/16. As I stated in my previous mail, 1.2.4.1/24 gets
registered after the "reply"(1.2.3.4/16) has been sent to the ingress
NHC. So initially NHS could not have found 1.2.4.1/24 entry in its
registered cache and therefore cannot return 1.2.4.1/24 to the ingress
NHC.So ingress NHC would use the sub-optimal route for some time.

Of course, when ingress NHC refreshes its resolution request, that time
NHS will find both 1.2.3.4/16 and 1.2.4.1/24 and therefore can return
1.2.3.4/24(LOGIC: update 16 becoz there is a /24 entry) and also return
1.2.4.1/24. 

One alternative to avoid suboptimal routing could be that egress NHS may
purge the ingress NHC when 1.2.4.1/24 registers to inform the ingress
NHC that 1.2.3.4/16 is not a correct resolution. The ingress NHC may
then retry resolution and get both 1.2.3.4/24 and 1.2.4.1/24.

-regards
Archana

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