Fred,
Inline....
Ron
>
> Message: 1
> Date: Tue, 14 Apr 2015 16:24:00 +0000
> From: "Templin, Fred L" <[email protected]>
> To: "[email protected]" <[email protected]>
> Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-gre-ipv6-07.txt
> Message-ID:
> <2134F8430051B64F815C691A62D9831832E483BE@XCH-BLV-
> 504.nw.nos.boeing.com>
>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi, in Section 3.2 there is now specification for sending a 1280 byte probe
> packet to test the path between the ingress and egress. The stated goal is to
> ensure that a 1280 byte packet can traverse the tunnel without
> fragmentation.
>
> However, if there are other tunnels on the path from the first tunnel ingress
> toward the corresponding egress, it is possible that another tunnel could be
> fragmenting and reassembling the probe packet before it arrives at the final
> egress. And, fragmentation and reassembly closer to the middle of the
> network is much worse than fragmentation and reassembly nearer the
> edges of the network.
>
[RPB]
In that case, configure the inner tunnel so that it can't fragment the delivery
packet and configure the outer tunnel so that it can.
> This is why I have proposed a new "Don't Fragment" bit in the GRE header.
> It can be set by the first tunnel ingress to tell other tunnels not to
> fragment
> the packet that is being used as a probe. Fragmentation and reassembly of
> probe packets must be avoided if we are to avoid fragmentation and
> reassembly of data packets.
[RPB]
That's a fine idea, but because it isn't backwards compatible, it isn't GRE.
>
> Also, it might be worth noting that this is not the first time a tunnel
> loopback
> test packet has been specified. A similar facility is specified in Section 8
> of
> RFC5969.
[RPB]
GRE Liveness testing isn't specified in any RFC, but it has been widely
deployed by many vendors for over a decade.
Ron
>
> Thanks - Fred
> [email protected]
>
>
*****
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