On 03/28/12 10:48, Satoru Matsushima wrote:
>> On the contrary, there is a big difference. The difference is that you are only concerned with L3. L4 can change: UDP, TCP, ICMP, STCP, DCCP, etc, etc, etc. You need a lot of code to handle all existing transport protocols, and you still can't handle future protocols that people might develop.
>>
>> Checksum neutrality is a *big* advantage.
>
> Cool. How many protocols we should support for just a *transition* mechanism?
The way I see it, IPv4-over-IPv6 (e.g. 4rd) has potential to be used for
a longer time than IPv6-over-IPv4 (e.g. 6rd). Operators will need to
keep providing clients with residual IPv4 for a potentially
loooooooooooong time. So we need to be really careful to get this right,
because we'll be stuck with what we design for a long time.
So you have two options:
a) checksum neutrality
- no code specific to each transport prototol
- supports all current and future transport protocols
b) checksum non-neutrality
- additional code necessary for each transport protocol
- limited set of supported transport protocols
Less code, more transport protocols. I think the choice is easy.
There's a reason NPTv6 and NAT64 chose checksum neutrality...
Simon
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