Re: [mpls] Concerns about ISD

[Haoyu Song <[e-mail]>]

Hi John,

Please read our EHI  draft. https://datatracker.ietf.org/doc/html/draft-song-mpls-eh-indicator-04
While we prefer to use a SPL to indicate EH among all the options , we never said “only”.

Best regards,
Haoyu

From: John E Drake <[e-mail]>
Sent: Friday, April 15, 2022 11:16 AM
To: Tony Li <[e-mail]>
Cc: Haoyu Song <[e-mail]>; Tianran Zhou <[e-mail]>; [e-mail]
Subject: Re: [mpls] Concerns about ISD

The last time this was discussed, Haoyu indicated that it was a requirement that the EHI must be the only SPL in the label stack, which seems a bit restrictive.
Sent from my iPhone


On Apr 15, 2022, at 2:08 PM, Tony Li <[e-mail]<mailto:[e-mail]>> wrote:

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Hi Haoyu,


Please take a look at our EH draft if you haven’t yet. The mechanism is there and the essence is that it doesn’t tamper the MPLS label stack and label semantics. That’s why I say PSD is least intrusive.


Thank you, I was unaware of it and have now looked at it.  If I understand it correctly, the EHI is the trigger to look for extension headers, all of which are in PSD.  Again, the parsing performance is a linear read to find the bottom of stack.

While it may be minimally intrusive to the label stack semantics, that doesn’t seem like a good trade-off for the performance penalty.

On a separate point, I have deep concerns about the encoding efficiency of the extension headers.  We can talk about this if and when it becomes relevant.

Tony