Re: [Dime] Questions regarding RFC 6733

Hi Ajinkya,

This will depend on how your "fork" is implemented and it is why it is considered as "implementation-specific".
If N instances are sharing the same Diameter id (DiamId 1), you may have a way to consider the connection up as long as one instance inside the peer is available and active. In that case, there is no impact for other diameter peers in the network. For the outside world, there would be only one transport connection opened with "DiamId 1", independently of the number of instance behind "DiamId 1".

Lionel

De : DiME [mailto:dime-bounces@ietf.org] De la part de Ajinkya Joshi
Envoyé : mercredi 8 mars 2017 10:37
À : jouni.nospam
Cc : dime@ietf.org
Objet : Re: [Dime] Questions regarding RFC 6733

On Tue, Mar 7, 2017 at 10:04 PM, jouni.nospam <jouni.nospam@gmail.com<mailto:jouni.nospam@gmail.com>> wrote:
hi,

> On Mar 7, 2017, at 3:01 AM, Ajinkya Joshi <ajoshi@definitionnetworks.com<mailto:ajoshi@definitionnetworks.com>> wrote:
>
> Hello,
>
> I have following questions regarding diameter RFC 6733, I would really appreciate if someone can help me with these.
>
> 1. Regarding diameter peer state machine -
>
>     Section 5.6.1 (Peer State Machine --> Incoming connections) mentions that Origin-host is used for     identifying peer state machine and as per state machine, once it moves into I-Open, new CER is       rejected. This concludes, that there can't be more than one transport connections with same               diameter host (as specified by Origin-host).
>
>     Section 2.1 (Transport) mentions that "A given Diameter instance of the peer state machine MUST      NOT use more than one transport connection to communicate with a given peer, unless multiple        instances exist on the peer, in which, case a separate connection per process is allowed."
>
>      Questions --
>       • Does section 2.1 implicitly assumes that multiple diameter instances (within a peer) would correspond to different diameter host ? Otherwise, it could contradict with section 5.6.1

it assumes one peer connection per peer state machine. so if you have a way to ‘fork’ a new peer instance with its own peer state machine per incoming connection then having “multiple instances’ is possible even if the diameteridentity is the same.

[ajoshi] If we fork a new peer instance with same diameteridentity, won't it create problems as per peer state machine? Because, you would have separate transport connection for each of them and each transport connection needs capability exchange and as per peer state machine, there can be only one capability exchange. I am inferring this based on section 5.3 which says "When two Diameter peers establish a transport connection, they MUST exchange the Capabilities Exchange messages". Am I missing something here? Or is it the case that two peers (identified based on their respective diameter host-names) would perform capability exchange only once, irrespective of number of transport connections they have?

>       • If multiple transport connections (towards the same peer) are allowed per diameter host, is it expected that peer would do load balancing between them? (There is a connection load balancing section in RFC 3539 - Section 3.4.3)

what you do and how you manage ‘multiple instances’ if more or less left for implementation to decide. i always considered it as a node internal compute load balancing mechanism i.e., to distribute the compute to separate cores/blades etc.

> 2. Regarding diameter peer failback procedure -
>
>       Section 5.5.4 mentions "a connection request should be periodically attempted with the failed              peer in order to re-establish the transport connection"
>
>       Question --
>
>       • If the failed peer is dynamically discovered via DNS lookup, is it expected that peer would perform DNS query before trying to establish the connection again? Or DNS lookup is driven only by TTL field received in the prior DNS answer ?

up to your implementation and dns resolver implementation.

- jouni

> --
> Regards,
> Ajinkya Joshi
> _______________________________________________
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> DiME@ietf.org<mailto:DiME@ietf.org>
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--
Regards,
Ajinkya Joshi

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