Hi Tina,

Le 2012-03-07 à 09:58, Maoke a écrit :

> 
> 
> 2012/3/7 Tina TSOU <[email protected]>
> 
> 
> Sent from my iPad
> 
> On Mar 6, 2012, at 2:24 AM, "GangChen" <[email protected]> wrote:
> 
> > Hello Tina,
> >
> > Could you help to clarify the sentence:
> >
> >   *1 MAP and divi-pd provide better security than 4rd-U, because they
> >   provide more variation in port set definition.
> >
> > I guess they should have similar features on security
> Agreed. No much difference between MAP, divi-pd, and 4rd-U with regard to 
> security. So I propose to remove this sentence.

+1 (see below)

> 
> well, *better security* might be an inaccurate expresssion. i suppose MAP 
> provides better flexibility than 4rd-U. personally, i understand the reason 
> of 4rd-U requiring fixed offset (4bits) is to support the longest-match of 
> port for CE-finding in the mesh mode (i.e., the MAX PSID). it is a tradeoff. 
> without the fixed offset, longest-match fails for the PSID matching and there 
> must be a way of distributing CE's PSID to other CEs. however,


> it does also confuses me that the newest 4rd-U draft doesn't mention the MAX 
> PSID feature (or maybe i missed something).

The max PSID feature, present in 4rd-u-00 and -01 (i.e. before IETF 82), was 
abandoned during the Taipei meeting (November 2011)
It no longer appeared in -02 (December 29).

Reasons of the 4rd-u fixed offset are (ref. sec 4.3 of -04):
"NOTE: The choice of the PSID position in Port fields has been guided by the 
following objectives: (1) for fairness, avoid having any of the well-known 
ports 0-1023 in the port set specified by any PSID value (these ports have more 
value than others); (2) for compatibility RTP/RTCP [RFC4961], include in each 
port set pairs of consecutive ports; (3) in order to facilitate operation and 
training, have the PSID at a fixed position in port fields; (4) in order to 
facilitate documentation in hexadecimal notation, and to facilitate operation 
and training, have the PSID at a fixed position in port fields; (4) in order to 
facilitate documentation in hexadecimal notation, and to facilitate operation 
and training, have the PSID at a fixed position in port fields; (4) in order to 
facilitate documentation in hexadecimal notation, and to facilitate."

Hope it clarifies.

Regards,
RD



>  
> >
> > Gang
> >
> > 2012/3/2, Tina TSOU <[email protected]>:
> >> Dear all,
> >> You may be interested to comment on
> >> http://datatracker.ietf.org/doc/draft-tsou-softwire-port-set-algorithms-analysis/
> >>
> >> Abstract:
> >>  This memo analyses some port set definition algorithms which
> >>  encode port set information into IPv6 address so as to support
> >>  stateless IPv4 to IPv6 transition technologies, e.g. 4rd-U and MAP.
> >>
> >>
> >> Tetsuya, Simon and Tina
> >>
> >> _______________________________________________
> >> Softwires mailing list
> >> [email protected]
> >> https://www.ietf.org/mailman/listinfo/softwires
> >>
> _______________________________________________
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