Re: [Dime] Last Call: <draft-ietf-dime-agent-overload-08.txt> (Diameter Agent Overload and the Peer Overload Report) to Proposed Standard

Misha Zaytsev <misha.zaytsev.rus@gmail.com> Tue, 17 January 2017 20:23 UTC

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From: Misha Zaytsev <misha.zaytsev.rus@gmail.com>
Date: Tue, 17 Jan 2017 23:23:41 +0300
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Subject: Re: [Dime] Last Call: <draft-ietf-dime-agent-overload-08.txt> (Diameter Agent Overload and the Peer Overload Report) to Proposed Standard
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Hi All,

Here are my comments/questions to an agent overload draft.
This the first part. Later on I will complete my review and send out the
second portion of the comments.

1. section 1 (editorial) removed "is" before "feasible".

In the base specification, the goal is to handle abatement of the
   overload occurrence as close to the source of the Diameter traffic as
   feasible.


"scenaios" -> "scenarios"

The Peer overload report type is
   defined in a generic fashion so that it can also be used for other
   Diameter overload *scenarios*.


2. section 3.1.1 (editorial) replaced "were"-> "was"

In both of these cases, the occurrence of overload in the single
   agent must by handled by the client in a similar fashion as if the
   client *was* handling the overload of a directly connected server.


3. section 3.1.1 (question)

An appropriate error response is sent back to the originator
   of the request.

Who sends "an appropriate" error response" in this case?

4. section 3.1.2 (editorial) changed "to"->"the"

When the client has an active and a standby connection to the two
   agents then an alternative strategy for responding to an overload
   report from an agent is to change *the *standby connection to active and
   route all traffic through the new active connection.


5. section 3.1.3 (editorial)

An example of this type of deployment include*s* when there are Diameter
   agents between administrative domains.

6. section 3.1.3

There is no section 2.2. I guess section 3.1.2 was meant here, right?

Handling of overload of one or both of agents a11 or a12 in this case
   is equivalent to that discussed in section 2.2.


7. section 3.2.1

It is not clear which usage scenario is meant here.

   It is envisioned that abatement algorithms will be defined that will
   support the option for Diameter Endpoints to send peer reports.  For
   instance, it is envisioned that one usage scenario for the rate
   algorithm, [I-D.ietf-dime-doic-rate-control], which is being worked
   on by the DIME working group as this document is being written, will
   involve abatement being done on a hop-by-hop basis.


8. section 4

Why is throttling to be applied and not diversion (like in case of
redundant agents)?

In this scenario the reacting node should first handle the throttling of the
   overloaded host or realm.

"LOSS" Is it a new type defined in the scope of this draft?

Note: The goal is to avoid traffic oscillations that might result
      from throttling of messages for both the HOST/REALM overload
      reports and the PEER overload reports.  This is especially a
      concern if *both reports are of type LOSS*.


9. section 5.1.1

Probably it is better to describe OC_PEER_REPORT feature in section 5.1?
Otherwise, it is used as a well-known one while it is the first place where
it is mentioned.

Also I think it is better to add more specific in this draft related to
peer report handling:
- define Peer Report Reacting Node and Peer Report Reporting Node terms
explicitly and use them through the draft and especially starting from
section 5.1
- add "Peer Report" prefix to all the described procedures
Example: Capability Announcement -> Peer Report Capability Announcement

10. section 5.1.1/general

"DiameterIdentity" and "Diameter identity"
My proposal is to use one term through the spec.

Under "DOIC node", an agent is meant here?

 When an agent relays a request that includes a SourceID AVP in the
   OC-Supported-Features AVP, a DOIC node that supports the
   OC_PEER_REPORT feature MUST remove the received SourceID AVP and
   replace it with a SourceID AVP containing its own Diameter identity.


My proposal is to use peer report reacting node here re-phrasing this
statement below in the following way:

 When relaying a request that includes a SourceID AVP in the
   OC-Supported-Features AVP, a peer report reacting node MUST remove
the received SourceID AVP and
   replace it with a SourceID AVP containing its own DiameterIdentity.

11. section 5.1.2

added the missed "to"
changed "PEER_REPORT"-> "PEER"

Note: The transaction state is used when the DOIC node is acting
      as a peer-report reporting node and needs *to *send OC-OLR reports of
      type *PEER *in answer messages.  The peer overload reports
      are only included in answer messages being sent to peers that
      support the OC_PEER_REPORT feature.


"Diameter ID" term is not clarified anywhere.
Re-phrased the appropriate statement a little bit, changed "Diameter
ID"->"value"
Also there are other places in the draft where "Diameter ID" term is used.

The peer supports the OC_PEER_REPORT feature if the received request
   contains an OC-Supported-Features AVP with the OC-Feature-Vector with
   the OC_PEER_REPORT feature bit set and with a SourceID AVP with a
   value that matches the DiameterIdentity of the peer from which
   the request was received.


Agent is meant under "reporting node" here?

Should not SourceID AVP not just stripped from the relayed answer, but
replaced with the SourceID AVP containing the DiameterIdentity of the agent
supporting OC_PEER_REPORT feature?

When an agent relays an answer message, a reporting node that
   supports the OC_PEER_REPORT feature MUST strip any SourceID AVP from
   the OC-Supported-Features AVP.


Hard to follow what was wanted to say here:
Corrected the statement, but this is just my best guess.

The OC-Peer-Algo AVP MUST indicate the overload abatement
   algorithm that the reporting node wants the reacting nodes to use
   *when *the reporting node send*s* a peer overload report as a result of
   becoming overloaded.


Should not we add a separate if- statement for the case when the peer does
not support OC_PEER_REPORT feature when sending an answer message?

12. section 5.1.1 and 5.1.2

Probably it is more helpful to illustrate OC_PEER_REPORT feature CA using
sequence diagrams like in the load info conveyance draft.

13. general.

What about to use the writing for the same terms through the spec?
Example1: "DOIC node" and "DOIC Node"
Example2: "peer-report reporting node" and "peer report reporting node"

14. section 5.2.1.2, 5.2.2, 5.2.3 and general

"peer-type OCS" and "peer report OCS" define the same term?
Why not to use only one?

Another example: "peer report" and "peer report-type" and "report of type
PEER"

15. section 5.2.3

Probably it is better to re-phrase this statement a little bit + corrected
the misprints.

If a *peer report* reacting node receives an OC-OLR AVP of type peer and the
SourceID matches the *DiameterIdentity *of the peer from which the *report*
was received then the report was *generated *by the peer.


Similar comment + corrected misprints for the next statement:

If a peer report reacting node receives an OC-OLR AVP of type peer and the
SourceID does not match the *DiameterIdentity *of the peer from which
the*report *was received then the reacting node MUST ignore the
overload
report.


Also I think it is useful to use one wording for the same term:
"Peer Report OLR", "OC-OLR AVP", "OLR"
Let's use a generic one "peer report"?

Just minor comment: "the existing..." and "a new overload condition" for
all occurrences if my English is correct.

16. section 5.2.3

How may it happen that peer report reacting node receives a peer report not
from the peer that generated it?
Peer reports can be sent only to peer report reacting node, right? And peer
reports are not relayed, right?

Best regards,

/Misha


2017-01-09 17:35 GMT+03:00 The IESG <iesg-secretary@ietf.org>rg>:

>
> The IESG has received a request from the Diameter Maintenance and
> Extensions WG (dime) to consider the following document:
> - 'Diameter Agent Overload and the Peer Overload Report'
>   <draft-ietf-dime-agent-overload-08.txt> as Proposed Standard
>
> The IESG plans to make a decision in the next few weeks, and solicits
> final comments on this action. Please send substantive comments to the
> ietf@ietf.org mailing lists by 2017-01-23. Exceptionally, comments may be
> sent to iesg@ietf.org instead. In either case, please retain the
> beginning of the Subject line to allow automated sorting.
>
> Abstract
>
>
>    This specification documents an extension to RFC 7683 (Diameter
>    Overload Indication Conveyance (DOIC)) base solution.  The extension
>    defines the Peer overload report type.  The initial use case for the
>    Peer report is the handling of occurrences of overload of a Diameter
>    agent.
>
> Requirements
>
>
>
> The file can be obtained via
> https://datatracker.ietf.org/doc/draft-ietf-dime-agent-overload/
>
> IESG discussion can be tracked via
> https://datatracker.ietf.org/doc/draft-ietf-dime-agent-overload/ballot/
>
>
> No IPR declarations have been submitted directly on this I-D.
>
>
> The document contains these normative downward references.
> See RFC 3967 for additional information:
>     draft-roach-dime-overload-ctrl: A Mechanism for Diameter Overload
> Control (None - )
> Note that some of these references may already be listed in the acceptable
> Downref Registry.
>
>
> _______________________________________________
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>