Re: [Last-Call] Genart last call review of draft-ietf-dnsop-dns-tcp-requirements-12

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Hi Duane, 

Thank you for your answer and for addressing my concerns. I am fine with the proposed resolutions.

Regards,

Dan


On Tue, Sep 7, 2021 at 7:46 PM Wessels, Duane <dwessels@xxxxxxxxxxxx> wrote:
Dan, thanks for the review.  Responses are inline.



> On Sep 1, 2021, at 3:12 AM, Dan Romascanu via Datatracker <noreply@xxxxxxxx> wrote:
>
>
> Minor issues:
>
> 1. In Section 4.1:
>
>> DNS clients MAY also enable TFO when possible.
>
> Maybe I do not fully understand the intent here, but 'MAY ... when possible'
> sounds like a SHOULD to me.


Originally this was "SHOULD ...  when possible" (meaning when
implemented/supported) but after conversations with tcpm this was changed
to MAY.  To avoid confusion with "when possible" I suggest we just drop
it so it will just say "DNS clients MAY also enable TFO."



>
> 2.In Section 4.2
>
>>  DNS server software SHOULD provide a configurable limit on the total
>   number of established TCP connections.  If the limit is reached, the
>   application is expected to either close existing (idle) connections
>   or refuse new connections.  Operators SHOULD ensure the limit is
>   configured appropriately for their particular situation.
>
>   DNS server software MAY provide a configurable limit on the number of
>   established connections per source IP address or subnet.  This can be
>   used to ensure that a single or small set of users cannot consume all
>   TCP resources and deny service to other users.  Operators SHOULD
>   ensure this limit is configured appropriately, based on their number
>   of diversity of users.
>
> The lack of recommendations about how these limits should be set would leave
> less experienced operators in the dark. There is not even a sentence like 'This
> document does not offer advice on particular values for such a limit' as for
> other parameters in the same section. From an operators point of view I would
> prefer a recommendation or one or more examples of how these limits can be set
> in real life cases.

Other reviewers called this out as well so I have added some recommended values.

For the limit on total number of connections: "Absent any other information,
150 is a reasonable value for this limit in most cases."

For the limit on connections per source address: "Absent any other
information, 25 is a reasonable value for this limit in most cases."

For the timeout on idle connections: "Absent any other information, 10
seconds is a reasonable value for this timeout in most cases."


>
> Nits/editorial comments:
>
> 1. Sections in the document that are obviously for informational pursposes
> should be clearly marked so (like 'This section is included for informational
> purposes only'). For example Section 2.

Done.


>
> 2. In Section 3:
>
> Regarding the choice of limiting the resources a server devotes to
>   queries, Section 6.1.3.2 in [RFC1123] also says:
>
>      "A name server MAY limit the resources it devotes to TCP queries,
>      but it SHOULD NOT refuse to service a TCP query just because it
>      would have succeeded with UDP."
>
>   This requirement is hereby updated: A name server MAY limit the
>   resources it devotes to queries, but it MUST NOT refuse to service a
>   query just because it would have succeeded with another transport
>   protocol.
>
> Similar alignment of the old and new text is desirable. Even using the OLD /
> NEW format.

Good point.  Section 3 now looks like this:

   Section 6.1.3.2 in [RFC1123] is updated: All DNS resolvers and
   servers MUST support and service both UDP and TCP queries.

   o  Authoritative servers MUST support and service all TCP queries so
      that they do not limit the size of responses to what fits in a
      single UDP packet.

   o  Recursive servers (or forwarders) MUST support and service all TCP
      queries so that they do not prevent large responses from a TCP-
      capable server from reaching its TCP-capable clients.

   Furthermore, the requirement in Section 6.1.3.2 of [RFC1123] around
   limiting the resources a server devotes to queries is hereby updated:

   OLD:

      A name server MAY limit the resources it devotes to TCP queries,
      but it SHOULD NOT refuse to service a TCP query just because it
      would have succeeded with UDP.

   NEW:

      A name server MAY limit the resources it devotes to queries, but
      it MUST NOT refuse to service a query just because it would have
      succeeded with another transport protocol.



FYI we are tracking this in github at https://github.com/jtkristoff/draft-ietf-dnsop-dns-tcp-requirements/pull/4/files if that is helpful.

DW

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