more comments...

Jessica Yu <jyy at merit.edu> writes
 *  >>Laurent Joncheray <lpj at merit.edu> writes:
 *   >* > Well this is only in the interas-out syntax where we agreed pref made
 *  
 *   >* > no sense for outbound announcements. Too protocol specific. 
 *   >* > The "time to converge" shouldn't be taken as a proposal. 
 *   >* 
 *   >*     We agreed on as-out. Not interas-out.
 *   >*
 * >Well then fine - say why we need it. 
 * 
 * Tony,
 * 
 * Why we need it?  Think about the following example:
 * 
 * AS1 and AS2 interconnects at two different locations at connection point c1 
 * and c2.
 * AS2 likes to have AS1 send traffic to x via c1 as primary c2 as secondary.  
 * It can 
 * either grab the phone and call AS1 asking:  'please put in your interas-in s
 * tatement
 * to accept x at c1 with prefernce 1 and c2 with prefernce 2' or just put in i
 * ts
 * own interas-out statement using the <pref> to specify that.  Now the point o
 * f
 * express policy and register it is to avoid phone calles to communicate polic
 * ies.
 * Adding metric/pref in interas-out (or as a matter of fact as-out) is a win.

Our main argument against preferences on outgoing policies has always
been that this is the ONLY bit of policy information in the whole
object that you CANNOT control. You can specify whatever you want, it
completely depends on your neighbor to do the right thing. You have no
control, your neighbor has. Besides that, the metric is *very*
protocol dependent. In the case of BGP-4, there should be at least two
metrics. Which is the one specified here? The definition in my mind is
too vague, AND it is the only bit of policy that you actually cannot
enforce. 

 * In the NSFNet environment, we have many ASs interconnects with AS690 with mu
 * ltiple
 * locations and using the same AS number now.  Currently they use NCAR to expr
 * ess
 * the preference policy, it is equivenlunt to express their as-out (interas-ou
 * t)
 * policy.

I do not agree. The NACR does not specify their as-out, it specifies
AS690's as-in. In any peer-peer agreement you have to communicate the
desired policy to get it to work. AS690 enforces the ordering of
announcements, not the regional. This is the whole point.

 * In short, we really need the metric/pref be added in at least interas-out. 

As you see, I do not agree. As far as I see, this metric is only
needed because the gated config supports something like this. I
however would prefer to keep a consistent model (ie I can enforce
everything I register) than bending consistency to accomodate one type
of router configuration. For the same reason, people using BGP-4 on
cisco's may want two metrics. As proposed before, I much rather put
all this (non-enforcable and very protocol dependent) information in a
completely seperate place that clearly defines what they are and in
what context. Something like a "bgpmetrics" attribute or something in
that style. This can be clearly marked as local information,
non-enforcable and as the name shows, protocol dependent.

-Marten



-------- Logged at  Fri May 27 23:07:52 MET DST 1994  ---------