-----Original Message----- From: Masataka Ohta [mailto:mohta@necom830.hpcl.titech.ac.jp] Sent: Monday, June 04, 2012 4:40 PM To: Templin, Fred L; nanog@nanog.org Subject: Re: IPv6 day and tunnels
Templin, Fred L wrote:
I'm not sure that a randomly-chosen "skip" value is even necessary.
It is not necessary, because, for ID uniqueness fundamentalists, single event is bad enough and for most operators, slight possibility is acceptable.
Outer fragmentation cooks the tunnel egresses at high data rates.
Have egresses with proper performance. That's the proper operation.
How many core routers would be happy to reassemble at line rates without a forklift upgrade and/or strong administrative tuning?
End systems are expected and required to reassemble on their own behalf.
That is not a proper operation of tunnels.
Why not?
Thus, don't insist on having unique IDs so much.
Non-overlapping fragments are disallowed for IPv6, but I think are still allowed for IPv4. So, IPv4 still needs the unique IDs by virtue of rate limiting.
Even though there is no well defined value of MSL?
MSL is well defined. For TCP, it is defined in RFC793. For IPv4 reassembly, it is defined in RFC1122. For IPv6 reassembly, it is defined in RFC2460.
I'm talking about not protocol recommendation but proper operation.
I don't see any operational guidance recommending the tunnel ingress to configure an MRU of 1520 or larger.
I'm talking about not operation guidance but proper operation.
The tunnel ingress cannot count on administrative tuning on the egress - all it can count on is reassembly of 1500 or smaller and it can't count on good performance even at those levels.
Proper operators can, without any guidance, perform proper operation.
No amount of proper operation can fix a platform that does not have adequate performance. And, there is no way for the tunnel ingress to tell what, if any, mitigations have been applied at the egress. Thanks - Fred fred.l.templin@boeing.com
Masataka Ohta