Subject: [mpls] Spencer Dawkins' Discuss on draft-ietf-mpls-oam-ipv6-rao-03: (with DISCUSS)

From: "Spencer Dawkins" <[email-masked]>
Date: Mon, 16 Feb 2015 13:49:18 -0800

Spencer Dawkins has entered the following ballot position for
draft-ietf-mpls-oam-ipv6-rao-03: Discuss

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DISCUSS:
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This Discuss ballot is probably more accurately a "Please clue in a TSV
AD who is trying to pattern match and failing" ballot, and likely quick
to resolve.

But, I'm looking at this text:

4.  Updates to RFC 4379

   [RFC4379] specifies the use of the Router Alert Option in the IP
   header.  Sections 4.3 and 4.5 of [RFC4379] are updated as follows:
   for every time in which the "Router Alert IP option" is used, the
   following text is appended:

      In case of an IPv4 header, the generic IPv4 Router Alert Option
      value 0x0 [RFC2113] SHOULD be used.  In case of an IPv6 header,
                          ^^^^^^
      the IPv6 Router Alert Option value TBD1 allocated through this
      document for MPLS OAM MUST be used.
      
When I click over to Section 4.3 of [RFC4379], I see this text:

4.3.  Sending an MPLS Echo Request

   An MPLS echo request is a UDP packet.  The IP header is set as
   follows: the source IP address is a routable address of the sender;
   the destination IP address is a (randomly chosen) IPv4 address from
   the range 127/8 or IPv6 address from the range
   0:0:0:0:0:FFFF:127/104.  The IP TTL is set to 1.  The source UDP port
   is chosen by the sender; the destination UDP port is set to 3503
   (assigned by IANA for MPLS echo requests).  The Router Alert option
   MUST be set in the IP header.
   ^^^^
   
Could you help me understand whether this is really a MUST in Section 4.3
of [RFC4379] that is morphing into a SHOULD for IPv4 and remaining a MUST
in IPv6?

I have the same confusion in Section 4.5, but I'm betting the same answer
applies.

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From: "Carlos Pignataro (cpignata)" <[email-masked]>
Date: Mon, 16 Feb 2015 22:06:49 +0000

Hi, Spencer,

Thanks for the question — please see inline.

On Feb 16, 2015, at 4:49 PM, Spencer Dawkins <[email-masked]<mailto:[email-masked]>> wrote:

4.  Updates to RFC 4379

Right — Section 4.3 of RFC 4379 says “ The Router Alert option MUST be set in the IP header” and Section 4.5 of RFC 4379 says “IP header MUST contain the Router Alert IP option”.

However, these Sections do not specify what value ought to be used within the option.

That is, they specify the option (which contains a value) MUST be used, but are silent as to which value to use. This new draft closes that gap, and specifies that when the option is used (because of the MUST in 4379), then which values to use for IPv4 and IPv6 respectively.

In other words, this doc specifies the 2-octet value within https://tools.ietf.org/html/rfc2113#section-2.1 and https://tools.ietf.org/html/rfc2711#section-2.1

No. The MUST remains, and we are specifying what to do within the value when the option is used (following the 4379 MUST). We used MUST for the IPv6 value because it’s being defined here, and SHOULD for the IPv4 value because there are existing implementations and 4379 was focused on IPv4 assuming the value of 0x0.

Ditto — same answer.

Does this help?

Thanks,

Carlos.

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From: "Carlos Pignataro (cpignata)" <[email-masked]>
Date: Mon, 16 Feb 2015 22:06:49 +0000

Hi, Spencer,

4.  Updates to RFC 4379

Ditto — same answer.

Does this help?

Thanks,

Carlos.

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Mon, 16 Feb 2015 18:18:11 -0600

Hi, Carlos,

On Mon, Feb 16, 2015 at 4:06 PM, Carlos Pignataro (cpignata) <
[email-masked]> wrote:

>  On Feb 16, 2015, at 4:49 PM, Spencer Dawkins <
> [email-masked]> wrote:
>
>  Right — Section 4.3 of RFC 4379 says “ The Router Alert option MUST be
> set in the IP header” and Section 4.5 of RFC 4379 says “IP header MUST
> contain the Router Alert IP option”.
>
>  That is, they specify the option (which contains a value) MUST be used,
> but are silent as to which value to use. This new draft closes that gap,
> and specifies that when the option is used (because of the MUST in 4379),
> then which values to use for IPv4 and IPv6 respectively.
>
>  In other words, this doc specifies the 2-octet value within
> https://tools.ietf.org/html/rfc2113#section-2.1 and
> https://tools.ietf.org/html/rfc2711#section-2.1
>
>  No. The MUST remains, and we are specifying what to do within the value
> when the option is used (following the 4379 MUST). We used MUST for the
> IPv6 value because it’s being defined here, and SHOULD for the IPv4 value
> because there are existing implementations and 4379 was focused on IPv4
> assuming the value of 0x0.
>
>

Completely. I'm clearing.

Thanks!

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From: Spencer Dawkins at IETF <[email-masked]>
Date: Mon, 16 Feb 2015 18:18:11 -0600

Hi, Carlos,

Thanks!