[Anima] Re: pls comment: “Lightweight GeneRic Autonomic Signaling Protocol”(draft-zhu-anima-lightweight-grasp-00)

Brian E Carpenter <brian.e.carpenter@gmail.com> Thu, 11 July 2024 03:30 UTC

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Date: Thu, 11 Jul 2024 15:30:32 +1200
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To: 朱龙薇 <lwzhu@bupt.edu.cn>
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Subject: [Anima] Re: pls comment: “Lightweight GeneRic Autonomic Signaling Protocol”(draft-zhu-anima-lightweight-grasp-00)
Archived-At: <https://mailarchive.ietf.org/arch/msg/anima/qkY-f2NTjfJSs4-45cp11Y7Cpdw>

Hi Longwei,

I have a few questions:

#1:

>>  3.1. Reliable transmission for confirmable LW-GRASP messages 

...

>> If the LW-GRASP confirmable message does not get an acknowledgment within the retransmission timeout, then the message MUST be retransmitted, but there is no need to regenerate the Nonce, just keep it the same as the original message.

What happens if the recipient has accepted the message and processed it, but the acknowledgment is lost? Some GRASP messages (especially M_NEGOTIATE) are not idempotent, so simply repeating a message could be dangerous.

I think this requires some extra specification - the recipient must also cache the nonce in order to detect repeats. I think a repeat needs to be acknowledged, but not processed a second time.

#2:

I don't see a discussion of message integrity (i.e. the replacement for the TCP checksum). Are you relying on the UDP checksum? Is there a negative acknowledgment if there is a checksum error?

#3:

>>  4.2.1. LW-Objective option 

...

>> objective-num = 0..255

CBOR does not require you to limit this to 8 bits. So you could define it as larger, e.g. 16 bits, but start assigning from zero; that would make no difference on the wire unless you actually *needed* more than 256 values.

Also, do you expect the objectives to be standardised and registered like normal GRASP objectives, or will they be local? This needs to be explained. For example, if you wanted to use "PrefixManager" and "PrefixManager.Params" from RFC8992, would you give them numbers in addition? ("PrefixManager" = 10, "PrefixManager.Params" = 11)

#4:

>>  7. Security Considerations 

The security people insisted that in RFC 8990, we specified use of TLS even over the ACP. This was for defence against internal attackers. (I did implement an alternative, draft-carpenter-anima-quads-grasp, but it still needs a full crypto library.)

Regards
    Brian

On 05-Jul-24 01:29, 朱龙薇 wrote:
> Dear ANIMA WG members,
> 
> We have proposed the draft “Lightweight GeneRic Autonomic Signaling Protocol”(draft-zhu-anima-lightweight-grasp-00, https://datatracker.ietf.org/doc/draft-zhu-anima-lightweight-grasp/)
> 
> The draft aims to design a lightweight version of GRASP, i.e., LW-GRASP, with shortened messages and a message-oriented built-in reliability mechanism with the acknowledgment and retransmission capability based on Nonce. The LW-GRASP can work reliably over UDP, which avoids additional overhead caused by TCP，thus can be more suitable for resource-constrained IoT nodes. Furthermore, the possible IP-independent method for LW-GRASP is also discussed.
> 
> We would like to hear opinions from the WG. All kinds of comments are welcome.
> 
> Thanks
> 
>     Longwei Zhu
> 
> 
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> Anima mailing list -- anima@ietf.org
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[Anima] pls comment: “Lightweight GeneRic Autonom… 朱龙薇
[Anima] Re: pls comment: "Lightweight GeneRic Aut… Longwei Zhu
[Anima] Re: pls comment: “Lightweight GeneRic Aut… Brian E Carpenter