[Isis-wg] draft-ietf-isis-traffic-01.txt

[Don Fedyk]

Tony,

> -----Original Message-----
> From: Tony Li [mailto:tli@procket.com]
> Sent: Saturday, October 09, 1999 6:17 PM
> To: Fedyk, Don [BL3:2001-I:EXCH]
> Cc: isis-wg@external.juniper.net; te-wg@UU.NET
> Subject: Re: [Isis-wg] draft-ietf-isis-traffic-01.txt
> 
> 
> 
> Don,
> 
> 
> |  I have read the draft and the scanned the working group to 
> understand what 
> |  is happening to the metric(s).  While it makes sense that 
> the metrics for
> |  IS-IS
> |  were made larger and the 3 not commonly used metrics 
> eliminated, I do not 
> |  understand the proposal of a single Traffic Engineering Metric. 
> 
> 
> Well, it's what we felt was needed.  Note that the existing 
> metrics can
> continue to be used if the network 
> administrator/implementation allows it.
> There's no reason that you can't run the traffic engineering TLVs in
> parallel with the existing TLVs.
It is an either/or situation though for the new 24 bit metric and the old 6
bit
metrics, correct? 
The new connectionless metric does not have a specific traffic 
qualifier (such as delay, throughput etc) but I would assume its 
a combination of throughput and delay. Is this ever specified ?


We implemented thoughput and delay based routing on both a connectionless
and a path oriented system. 
The result for the connectionless system was that the delay based routing 
occupies forwarding table space for all possible destinations. 
We ended up implementing only two metrics. But with MPLS it is only 
a path minimization criteria during LSP selection.

> 
> 
> |  In my 
> |  experience multiple traffic engineering metrics for path 
> selection allow 
> |  better traffic engineering capabilities. 
> 
> 
> Please say more.  The customer base didn't request this flexibility
We are defining TE beyond just ISIS. In general it depends on the size 
of the network and the diversity of the links. The bandwidth allocation
records are a type of metric in a sense since they take the place of the
typical throughput based metric in a connectionless system. Of course
not all MPLS connections will specify traffic parameters.
I would be quite willing to elaborate on what metrics I think are useful 
and why in a small draft for the next IETF.

> 
> 
> |  Has any thought been given to multiple TE metrics? Can the 
> current proposal
> |  be expanded in the future ?
> 
> 
> One of the great glories of TLV encoding is the flexibility for future
> extensions.  ;-)

Agreed, but can also be one of its curses if we don't do it right.

> 
> Tony
>