Re: [Softwires] softwires-encaps-safi

"Pradosh Mohapatra (pmohapat)" <pmohapat@cisco.com> Thu, 08 May 2008 17:57 UTC

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From: "Pradosh Mohapatra (pmohapat)" <pmohapat@cisco.com>
To: Yakov Rekhter <yakov@juniper.net>
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Subject: Re: [Softwires] softwires-encaps-safi
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Hi Yakov,

| As I said in my original e-mail, here is a strawman proposal of what 
| should be added to the draft.
| 
| 1. If after the next hop resolution, the next hop does not have any
encaps info, 
| or does not have encaps info that matches the color of the prefix,
then 
| disposition of the packet is a matter of policy on the ingress PE.
| 
| 2. Each implementation SHOULD support the following (default) policy:
| 
|  1. Perform the usual procedures for finding the next hop, call it N.
|  
|  2. If no next hop is found, drop the packet and exit.
| 
|  3. If the policy is that there must be a color-matching encaps-safi,
then
|  
|     a. If there is none, remove from consideration all routes whose
next hop
|        is N, and go to 1.
|  
|     b. If there is a color-matching encaps-safi, tunnel the packet
according-
|        ly and exit.
| 
|  4. If the  policy  is  that there  does  not need  to  be a
color-matching
|    encaps-safi, then do whatever the policy says.

I guess I am having a bit of trouble trying to find out what is done in
control plane and what is done in data plane from the above text. There
is no difference during packet forwarding time from usual
(non-encap-safi)
cases (e.g. longest prefix match), but point 3.a above seems to suggest
otherwise (or I must have misunderstood the point).

I am also having trouble trying to find out the default policy part and
"if there is a policy" part in the text. E.g. point 4 above seems to
suggest there is a policy defined, whereas it's inside the block for
default policy definition.

I am wondering what part does not get covered by your first point, or
an augmented paragraph like the following:

If after the next hop resolution, the next hop does not have any encaps
info, 
or does not have encaps info that matches the color of the prefix, then 
disposition of the packet is a matter of policy on the ingress PE. In
the
absense of a local policy at the ingress PE, the default action is to
hold
such routes in unresolved state.

Rgds,
- Pradosh
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