Subject: RE: on documenting ECMP (was on the mpls oam framework)

From: "Naidu, Venkata" <[email-masked]>
Date: Tue, 18 Nov 2003 18:27:53 -0500

Peter,

-> It may be helpful if I reword my original point, which was:
-> 
-> 1) ECMP leads to non-deterministic behavior. We should 
-> develop OAM mechanisms that accept that as a given

  Agreed. ECMP is non-deterministic. Note also that non-determinism 
  leads to freedom and innovation. If there is no requirement
  to follow a standard and there is no requirement to interoperate
  with other vendor's implementation, vendor's can develop
  innovative mechanisms to support ECMP. Why are we restricting
  our community and trying to enumerate *current* practices ?

-> 2) Nevertheless, for certain types of traffic it might be 
-> possible to use tools from the connection-oriented world. 
-> E.g. if a Service Provider uses RSVP-TE to reserve bandwidth 
-> between two points, it will result in a path without 
-> intermediate splits. 

  No. Not always.

-> That last statement was my assumption. Curtis argued that 
-> there are exceptions, such as the case of hierarchical hops 
-> where a logical link consists of multiple physical links. 
-> You argue that path calculations can theoretically deal with 
-> ECMP splits. 

  Yes.

-> I stand corrected. I do wonder how routers will distribute 
-> traffic over the multiple paths with bandwidth guarantees. 
-> As far as I know, current hashing algorithms leave the 
-> packet sequence of micro flows intact, but there is nothing 
-> that prevents them from sending 90% of the traffic over one 
-> path and 10% over another. Or is there?

  No. Nothing preventing from doing so. But, finally, note that 
  any problem may be non-determinisic in nature, but proposed 
  solutions, algorithms and/or implementations are infact 
  deterministic for known-agreed-upon approximations/limitations.
  And a solution is not required to conver all degeneracies or corner
  cases. 

Venkata.

---

From: Curtis Villamizar <[email-masked]>
Date: Tue, 18 Nov 2003 20:43:59 -0500

In message <[email-masked]>, 
>   our community and trying to enumerate *current* practices ?

We are free to inovate and all of the ECMP implementations
interoperate with each other and the existance of any new ECMP
implementation which did nothing but ECMP but did it completely
differently would also interoperate.

>   And a solution is not required to conver all degeneracies or corner

All of the oxygen must be on one side of the room.  :-(

Curtis