Hi Satoru-san,
Le 18 sept. 2011 à 11:11, Satoru Matsushima a écrit :
> Mohamed, all,
>
> First, thanks for the analysis draft. It sounds good. Let me try to bring my
> thought.
>
> An interesting point is here. In the algorithms which define offset to
> exclude ports such as 1024, 4096 whatever, the efficiency of port utilization
> is decreased, which algorithm is 4rd, and complexity of calculation are
> increased, which algorithm is dIVI's modulo, when the number of CEs which
> share an address exceed the number of excluded ports.
>
> For example, in the case of that someone uses modulo with excluding under
> 1024 port, port-set ID is always placed at last 9 bits in a port if the
> number of CEs which share one address isn't exceed 1024. But when the number
> of CEs exceed 1024, complexity of modulo operation will be increased to
> calculate port set ID from port number at BR and CE. In the case of 4rd,
> which exclude under 4096 port, if CEs over 4096, which CEs share one address,
> 8K, 16K, 32K of ports are unusable respectively.
>
> To keep simple implementation and operation, I think that offset port and the
> maximum address sharing ratio should be same. So the question is what is the
> number. 1024 is small a little. 2048 or 4096? I think that first nibble of
> port to utilize offsetting is helpful for implementation and is easy to read
> in hex. So In my opinion, 4096 is adequate for both offset port and maximum
> sharing ratio.
Same view.
> If it would be applied to 4rd, a following figure could be depict. Port-set
> ID is always placed on right after the first nibble. CE's NAT needs to
> maintain just only fifteen port ranges, and BR and CE just remove first
> nibble to pick a port set ID from port number in a packet.
>
>
> 1 1 1 1 1 1
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> Port-set |h h h h|x x x x x x x x| |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |<head> |<-Port-set ID->|<-tail->
> 4bits max 12bits
> (0x1-0xF)
>
>
> Second, I think that the character differences of these analyzed algorithms
> come from where is port-set ID in a port number. Each algorithms is a result
> of labor to define where are port-set ID bits. I agree with last paragraph in
> section 2 that says 'the whole Port-Set may be deduced by extrapolation', so
> it would be predictable port set regardless of which analyzed algorithm
> generates.
>
> If I add one point to the analysis, that is 'Complexity of CE side NAT ports
> pool configuration and management', which NAT is already distributed to the
> fields. Several contiguous port ranges are helpful to configure and manage
> NAT ports pool. On the other hand, scattered scheme increases complexity of
> configuration and management as the number of ports in port set increased.
>
> So I think that having unique port set derivation for each stateless address
> sharing domain is important.
Same view.
> To make variation of port-set indexing, port-set ID mask option could be
> helpful. As I'm inspired by a discussion with Xiaohong, the port-set ID mask
> is used for which bits indicate port-set ID. That bits are fully configurable
> by each operator's domain. In terms of port-set ID mask configuration, the
> default port indexing is just one of configuration variation. Please see a
> following figure.
>
> 1 1 1 1 1 1
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> Port-set |h h h h| x x x x x x x |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |<head> | ^ ^ ^ ^ ^ ^ ^
> 4bits | | | | | | |
> (0x1-0xF) | | | | | | |
> | | | | | | |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> Port-set |0 0 0 0|0 1 0 1 1 0 1 1 0 1 1 0|
> ID mask +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> Option <------> <---------------------->
> must Port-set ID mask
> be (‘1’ indicates port-set ID bits)
> zero
>
>
>
> I have no draft for that yet, but I'd like to discuss at the interim meeting.
> Have a good weekend, hope to see you in Beijing, next week.
The next version of the 4rd-addmapping draft will document the following as
Port-set pattern (still working on it):
| | 1|
|0 |4 5|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x x x x| PSID |x x x x x|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
^ : : ^
| :<max 12 bits > |
| |
any value > 0 any value
It was discussed with mark last Wednesday, Sept 14, and he expressed great
interest.
Cheers,
RD
>
> cheers,
> --satoru
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