Subject: [Isis-wg] Problem for Support Frame Relay .

From: "Jorge" <[email-masked]>
Date: Mon, 17 Jan 2000 10:01:12 +0530

hi ,
    Now i met some problem about IS-IS on IPv4.We want to  implement the IS-IS to support the Frame Relay ,but i want to  know how i can implement it .Just as someone said in prio mails ,to regard the Frame Relay as multiple PPP links ,i think ,this method can be fitable for PVC, but how to deal with SVC,i don't know whether is means we don't need to care about SVC ,please  give some advice for me.  Thanks a lot!

---

From: Jeff Learman <[email-masked]>
Date: Mon, 17 Jan 2000 11:01:03 -0500

It's not important whether the links are PVCs or SVCs, it's

just important that they're "statically assigned".  In other

words, they have to be opened at startup time and in general,

kept open the whole time.  If you need to have the links open

and close on an as-needed basis, then you can't use IS-IS

to exchange routing information over them.  It's OK if you

want to shut down a link; just keep in mind that it won't be

opened automatically if it is needed for data traffic.

If the Frame Relay links are to end systems, then it isn't a

problem.  I'ts only a problem if the links are between routers,

and you need to exchange IS-IS routing information between them.

The reason is that IS-IS relies on the fact that all routers

in an area (or for level 2, all L2 routers in the domain) must

agree on the topology.  In order for this to work, they need to

be in constant communication.  Therefore, "dynamically assigned"

links, those that come up and go down on an as-needed basis,

aren't appropriate for links between routers (simply because

they're always needed.) 

Regards,

Jeff

At 10:01 AM 1/17/00 +0530, Jorge wrote: 

<excerpt><fontfamily><param>ËÎÌå</param><smaller>hi ,

    Now i met some problem about IS-IS on IPv4.We want to implement the
IS-IS to support the Frame Relay ,but i want to  know how i can implement
it .Just as someone said in prio mails ,to regard the Frame Relay as
multiple PPP links ,i think ,this method can be fitable for PVC, but how
to deal with SVC,i don't know whether is means we don't need to care
about SVC ,please  give some advice for me.  Thanks a lot!

</smaller></fontfamily>

</excerpt><<<<<<<<

____________________________________________________________________

  Jeff Learman                           Internet:     [email-masked]

  Engineering Manager                    Voice:     (734)-975-7323

  ONE (Open Networks Engineering, Inc)   Fax:       (734)-975-6940

  2725 South Industrial Pkwy, Suite 100

  Ann Arbor, MI  48104  USA

____________________________________________________________________

_______________________________________________
Isis-wg mailing list  -  [email-masked]
http://external.juniper.net/mailman/listinfo/isis-wg

---

From: Alex Zinin <[email-masked]>
Date: Mon, 17 Jan 2000 19:27:25 +0300

Hmmm...I wouldn't say so.
One can easily run IS-IS (or any other dynamic routing
proto) over on-demand circuits provided that the idle
timer doesn't close the VC before the next Hello PDU
is sent over it.

This is, actually, how these things are done in a number
of implementations.

As for Jorge's question---when SVCs are used, just make
sure the SVC is open before sending anything along it.
If it is not---generate a request for the circuit manager
asking it to open the VC. This is assumed to be done
in the IP-to-Layer2 part of the code, not in IS-IS.
Just like with PVSs, mapping statements for SVCs are
marked to be used for broadcast/multicast propagation.

HTH

Alex.

---

From: Alex Zinin <[email-masked]>
Date: Mon, 17 Jan 2000 19:54:53 +0300

Monday, January 17, 2000, 7:43:07 PM, Tony Przygienda <[email-masked]> wrote:
> again, first a problem statement would be nice to make sure
> we're all tackling the same problem.

Well, I think Jorge's initial messages are quite
clear on that---running IS-IS over NBMA media.
...and whichever issues related :)

> 2nd, Alex, you're oversimpliofying here ;-)

Tony, I'm not. I'm just correcting the statement
that on-demand VCs cannot be used with IS-IS.

>   Just "running"
> the protocol that way leads to extensive thrashing of up&downs
> of the circuit

Quoting myself:

"...provided that the idle timer doesn't close
the VC before the next Hello PDU is sent over it."

Note "doesn't" above.

I think you misunderstood me a bit. I'm not proposing
to open a VC for every packet and close it afterwards,
I'm saying one doesn't need to emulate PVCs using SVCs.

> [and therefore billing, if you don't get billed for your
> FR or ATM service, you may as well always leave the circuit up ;-)],
> a usable solution needs more thought like in OSPF
> (don't age bits, smart adjacency stay-up and couple of more details)

Agree.

Alex.

---

From: Tony Przygienda <[email-masked]>
Date: Mon, 17 Jan 2000 11:43:07 -0500

2nd, Alex, you're oversimpliofying here ;-)  Just "running"
the protocol that way leads to extensive thrashing of up&downs
of the circuit [and therefore billing, if you don't get billed for your
FR or ATM service, you may as well always leave the circuit up ;-)],
a usable solution needs more thought like in OSPF
(don't age bits, smart adjacency stay-up and couple of more details)

    thasnk
    -tony

---

From: Tony Przygienda <[email-masked]>
Date: Sun, 16 Jan 2000 23:52:41 -0500

Jorge wrote:

> hi ,    Now i met some problem about IS-IS on IPv4.We want to implement the IS-IS to support the Frame Relay ,but i want to  know how i can implement it .Just as someone said in
> prio mails ,to regard the Frame Relay as multiple PPP links ,i think ,this method can be fitable for PVC, but how to deal with SVC,i don't know whether is means we don't need to
> care about SVC ,please  give some advice for me.  Thanks a lot!

seems that the issue is being rised of whether we need support for ISIS in terms of P2M as OSPF has (and not of ISIS over IPv4
as the confusing topic and text suggests). It is a non-trivial (and not the most elegant and intuitive)
extension to the protocol and probably only worth doing if customer demand exists. I think I pinged once on this list
whether the potential customers have interest in P2M for ISIS with 0 answers. So I'd consider the issue not worth tackling
for the moment since if there is nobody to deploy it, why put the effort in ? Just run SVCs and FR in P2P mode.
However, if someone out there is implementing something proprietary to support P2M, it's probably much better that a draft
shows up, rather than struggle with proprietary, incompatible (and probably buggy due to lack of review by knowledgable parties)
later.

    thanks

    -- tony

---

From: Tony Przygienda <[email-masked]>
Date: Mon, 17 Jan 2000 11:26:07 -0500

> aren't appropriate for links between routers (simply because

I'm not clear which problem this thread is pursuiting. Are we talking
about the problem of partial meshes (P2M mode) or are we talking
about the problem of dynamic FR circuits (SVCs) coming up ?  Both problems
have solutions (P2M mode or dial-up link extensions that allow the
circuit to be shut down but adjacency maintained) but this whole
"ISIS and FR" needs a short problem definition before solutions are being
tossed around, I'd say.  More important even, is anyone from the customers
on this list interested in running ISIS over FR ?

    htankas
    -=-tony