Re: [Int-area] Call for adoption of draft-pignataro-intarea-gre-ipv6-01

[Joe Touch <[e-mail]>]

Hi, Ron (et al.),

The proposed change highlights exactly the problem: only minimal,
presumably transient versions of IPv6 should be limited to sending
packets no larger than 1280. I.e., only those versions are supposed to
omit source fragmentation.

Later in RFC2460 support for 1500-byte fragment reassembly is required,
so it's not appropriate to quote this section in isolation as the sole
recommendation for GRE.

Joe

On 12/5/2014 8:38 AM, Ronald Bonica wrote:
> Joe,
> 
> Would you agree to the following change?
> 
> OLD>
> Following guidance provided in Section 5 of [RFC2460], GRE ingress nodes SHOULD implement PMTUD, in order to discover and take advantage of PMTUs greater than the IPv6 required minimum (1280 octets).  However, a GRE ingress node MAY simply restrict itself to sending  packets no larger than 1280 octets, and omit implementation of PMTUD.
> <OLD
> 
> NEW>
> In as much as the GRE ingress is an IPv6 node, the following guidance from RFC 2460 applies:
> 
> " It is strongly recommended that IPv6 nodes implement Path MTU
>    Discovery [RFC-1981], in order to discover and take advantage of path
>    MTUs greater than 1280 octets.  However, a minimal IPv6
>    implementation (e.g., in a boot ROM) may simply restrict itself to
>    sending packets no larger than 1280 octets, and omit implementation
>    of Path MTU Discovery."
> 
> <NEW
> 
>> -----Original Message-----
>> From: Joe Touch [mailto:[e-mail]]
>> Sent: Thursday, December 04, 2014 1:42 PM
>> To: Ronald Bonica; [e-mail]
>> Subject: Re: [Int-area] Call for adoption of draft-pignataro-intarea-gre-ipv6-
>> 01
>>
>>
>>
>> On 12/4/2014 9:05 AM, Ronald Bonica wrote:
>> ...
>>> [RPB]
>>> The GRE ingress in an IPv6 source. As per RFC 2460, an IPv6 source
>>> MUST either execute PMTUD procedures or restrict itself to sending
>>> packets no longer than 1280 octets. How can you argue with that?
>>
>> RFC2460 includes sending IPv6 packets up to 1500 bytes that are reassembled
>> at the destination IP address - in the case of a tunnel, that's the egress.
>>
>> Each *fragment* must be no larger than 1280, agreed.
>>
>> PMTUD is recommended, not required (it's not a MUST).
>>
>> Joe