Subject: RE: tunnels are unavoidable for IPFRR

From: "Naidu, Venkata" <[email-masked]>
Date: Mon, 27 Sep 2004 15:23:28 -0400

Hi Albert,

-> First of all I feel tunnels are unavoidable for IPFRR for a 
-> number of reasons:

  I couldn't agree more. Bit, not MPLS tunnels. I have been 
  thinking of writing a small draft explaining the "impossibility 
  result" of solving IP FRR without using some form of tunneling. 

  After the topology database exchange is stabilized, the 
  snapshot of topology (i.e., view of the rest of the world) is 
  same from every router. After a single change in topology, It 
  is extremely difficult to re-construct the partial view of the 
  world to bypass the change. Because the snapshots differ from 
  every router as the time progress, till some stabilization point.

  First, we have to frame the problem correctly. Alex said that
  we are going to solve single link failure case where only two 
  routers are involved in a loop (U-turn). But, what about:

    * Single link addition
    * Node failure
    * Node addition and
    * Combination of such multiple failures

  In all of the above cases, there can be more than 2 routers in 
  a micro-loop for a brief period of time. Are we including this 
  case in the problem statement?

  To solve IPFRR effectively, I support using any type of 
  connection less tunneling techniques (IP-in-IP, for example)
  where there will be no extra signaling or maintenance of state 
  information on every hop a packet takes.

  Using connection oriented (including LDP) involves lot of 
  overhead in signaling and maintenance. RFC 3031, MPLS signaling
  architecture, clearly states that Loop detection is optional.
  If we choose to use MPLS as a solution for IP FRR, we end-up
  fixing micro-loops in MPLS signaling first.

Venkata.

_______________________________________________
Rtgwg mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/rtgwg

---

From: Albert Tian <[email-masked]>
Date: Tue, 28 Sep 2004 01:12:54 -0700

Hi, Naidu,

"Naidu, Venkata" wrote:

[snip] 

>   fixing micro-loops in MPLS signaling first.

In short, the answer is no, we don't have to fix micro-loops in MPLS first. RSVP
signaled explicit paths can have the full path specified so these are guaranteed
to be loopfree. For LDP signaled tunnels, you only need to use the ones that are
not affected by the given failure.

Thanks,

Albert