On 2018-11-14 12:35, Ole Troan wrote:
> Joe,
>
> For IPv4 part of the transport headers are now part of the network layer.
> Forwarding is done one address and port.
> I.e it's now part of 'normal' routing/forwarding. That's absolutely not the
> case. In IPv6 packets are delivered to hosts based on longest match on
> destination addresses, while for IPv4 it's a match IPv4 DA and DP. For ECMP,
> this is never an issue. ECMP can easily use a default for fragments and move
> on with life.
I am not sure why you bring in ECMP.
Most of Ron's text is based on load balancing - which is composed of two
cases: ECMP and end server.
> (It is actually a problem for ECMP, since fragmented and non-fragmented
> packets are prone to take different routes, but that seems to be far off
> topic).
That can't be any more a problem than different ports taking different
routes.
>> For end-system load balancing, similar defaults can work, but it's also
>> reasonable to expect that a device that acts on behalf of an end system that
>> way should do the work of an end system to reassemble.
>>
>> For DPI, reassembly - and sometimes restoration of the TCP data stream
>> across segments - is necessary anyway.
>>
>> For NAT, virtual reassembly is necessary.
>
> If the packet doesn't isn't TCP or UDP and the ports are available any IPv4
> packet will have a significantly higher drop probability.
There's a big difference between "higher" and "100%". The former is
always OK, the latter is not, at least it should not be silent.
> I'm fine with you not accepting that.
>
>> None of these are specific to IPv4; even in IPv6, flow IDs are not a magic
>> solution -- they need similar fragmentation support.
>
> Of course they are. One is IETF mandated and required to be able to forward
> packets, the other is not.
Both IPv4 and IPv6 are IETF mandated. Both require support for source
fragmentation both at the endpoints and in forwarding.
Joe
Ole
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