Re: [IPFIX] Options Templates, Templates, and related Data Sets sent in separate transport sessions

["Aitken, Paul" <[e-mail]>]

Garri,

 From the receiver's point of view, the different transport sessions are 
independent export streams which could come from different Exporters. 
The receiver can't tell whether these come from one exporter or two. The 
data in the "options" Export Stream cannot be scoped to data in the 
other stream as Template IDs are unique per Transport Session and the 
Observation Domain is locally unique to the Exporting Process and 
multiple EPs may be in play.

Only SCTP provides multiple streams; TPC and UDP do not. See section 6.1 
of RFC 5153.

P.


On 03/02/24 14:38, Garri Djavadyan wrote:
> Hi IPFIX experts,
>
>
> Recently, my colleagues and I faced an IPFIX exporter implementation
> that sends IPFIX messages with the Template and related Data Sets in
> one transport UDP session and the Options Template and related Data
> Sets in another transport UDP session (sourced from a different UDP
> port) to the same IPFIX collector port.
>
> While trying to understand this behaviour, I checked RFC7011 and a few
> related RFCs but could not find any notes suggesting use cases when it
> might be necessary. Also, I could not find any notes prohibiting this.
>
> However, we know of at least one use case when sending the
> aforementioned 4 IPFIX messages over 2 separate transport sessions is
> undesirable. For example, when multiple self-sufficient IPFIX
> collectors are listening on the same UDP socket using the socket option
> SO_REUSEPORT (for horizontal scaling), the kernel-level load-balancing
> algorithm can distribute 2 related sessions of the same exporter to
> different processes. As a result, the process receiving the Flow
> Records, cannot process them properly without the related Options. In
> theory, it can also happen in the environments where layer-4 load-
> balancers are used to distribute transport UDP sessions between IPFIX
> collecting hosts.
>
> Considering this, could you please help answer the following question?
>
> Did I interpret the IPFIX RFCs correctly and the mentioned exporter's
> behaviour is a compliant implementation?
>
> There is a note in the "Template Management" section 8 of RFC7011
> saying:
>
>     Options Templates and Templates that are related or interdependent
>     (e.g., by sharing common properties as described in [RFC5473])
>     SHOULD be sent together in the same IPFIX Message.
>
> but the Templates and the Options Templates in the case that I
> mentioned are not interdependant by the common properties per RFC5473.
>
>
>
> Thank you in advance!
>
>
> Kind regards,
> Garri Djavadyan
>   
>
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