Subject: RE: MED for Originated Routes

From: "Natale, Jonathan" <[email-masked]>
Date: Thu, 3 Oct 2002 17:30:11 -0400

Since no MED is equivalent to MED = 0 *in this case*, they are
interoperable.  But the base spec does not say what to set the
MED to for originated routes.  So I need to disagree, an
addition to the spec is called for.

-----Original Message-----
From: John G. Scudder [mailto:[email-masked]] 
Sent: Thursday, October 03, 2002 5:07 PM
To: Natale, Jonathan
Cc: [email-masked]'; Natale, Jonathan; [email-masked]
Subject: RE: MED for Originated Routes

At 4:55 PM -0400 10/3/02, Natale, Jonathan wrote:
>Juniper sends no MED for originated routes to IBGP, Cisco sends MED = 0 
>for originated routes to IBGP.  So maybe this needs to be clarified in 
>the Base spec.

The two behaviors are interoperable.  I don't think any change to the 
specification is called for.

--John

---

From: Mathew Richardson <[email-masked]>
Date: Thu, 3 Oct 2002 17:58:31 -0400

> Natale, Jonathan <[email-masked]> [Thu, Oct 03, 2002 at 05:30:11PM -0400]:

<snip>

The absence of an MED is equivalent to a MED of zero in all cases.

mrr

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From: Curtis Villamizar <[email-masked]>
Date: Thu, 03 Oct 2002 18:49:00 -0400

In message <[email-masked]
> addition to the spec is called for.

The two implementations don't do exactly the same thing.  They do
interoperate.  Someone owning some of each may want to know what will
be sent out by each router.

There is no need at all for the protocol spec to mandate what should
be sent out or document what various implementations do in this case.
The decisions made by routers in a BGP network of any configuration
will be self-consistent regardless of which behavior is used.  Routing
decisions will differ slightly if one router is replaced with the
other, but again will be consistent across the network.

Although there is no NEED for this, some people might find it
desirable to suggest a default behavior.  If we want to put something
in, I suggested a brief outline of what implementations do, noting
that although I thought the text was correct, there was no NEED to add
any of it.  We now have one variation from that which we can reflect
in any text we add, if we add any.

First we have to come to agreement on whether we need to add anything
at all.

Curtis

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From: Curtis Villamizar <[email-masked]>
Date: Thu, 03 Oct 2002 18:57:33 -0400

I just reread this and I wasn't clear about what I was saying.

If one router does something unusual like puts in MED=10 by default it
would still interoperate fine with other routers.  It might surprise
someone if it replaced another router that didn't do that.

There is no NEED to specify what to put into MED, just how to handle
MED (including whatever MED the router does put in) so that routing
decisions are consistent.

Repeating my last two paragraphs..

   Although there is no NEED for this, some people might find it
   desirable to suggest a default behavior.  If we want to put
   something in, I suggested a brief outline of what implementations
   do, noting that although I thought the text was correct, there was
   no NEED to add any of it.  We now have one variation from that
   which we can reflect in any text we add, if we add any.

   First we have to come to agreement on whether we need to add
   anything at all.

I hope that made more sense.

Curtis

In message <[email-masked]>, Curtis Villamizar