________________________________
From: Qiong [mailto:[email protected]]
Sent: Wednesday, August 17, 2011 12:29 AM
To: BOUCADAIR Mohamed OLNC-NAD-TIP
Cc: [email protected];
[email protected]
Subject: Re: [Softwires]
draft-operators-softwire-stateless-4v6-motivation
Hi, Med, and Nejc,
Please see inline.
You indeed loose agressive sharnig ratio, but you have somewhat
more
flexible addressing. Also, the CPEs can be then really simple
devices,
excluding any of the NAPT functionality, doing only stateless
encapsulation.
However, what you loose/gain is irrelevant for my point. I
think this
section should be modified in a way like the logging section or
any
other appropriate way, which explains, that this is not the
benefit of
the stateless nature, but rather the benefit of the static port
allocation.
Xiaohong: It's a trade-off between efficiency of log and
address sharing ratio for stateful solution. I do agree it's a good trade-off
for stateful, but one more good option for stateful doesn't make stateless less
valuable, so neither see it is too much to do with stateless motivation, nor
think it is necessary to document too much in the stateless motivation draft,
as long as the stateless motivation is more focused on the requirement of
stateless other than comparisons between the two.
[Qiong]: +1 Agree.
Med: Your point is valid and the text should be updated
accordingly. My comment aims to show that the comparison is not so that
trivial. We can claim the stateful with port ranges can provide similar
features as the stateless or the binding mode but we always forget to mention
this lead to loose one of the characteristics of the stateful. We captured a
similar discussion in
http://tools.ietf.org/html/draft-operators-softwire-stateless-4v6-motivation-01#section-4.2:
[Qiong]: In our situation, we do not regard aggressive sharing ratio as
a vital important feature since the static port multiplex ratio is already
enough for us. Besides, even for session-based CGN like ds-lite, we would still
prefer to pre-define port-range for customers because our centralized log
server can not deal with massive session-based log events. So it seems more
reasonable for us to adopt static port arrangement which can largely reduce the
log volume.
Xiaohong: I suppose you're saying it is valuable to you to have this
trade-off for stateful. Personally, I do see its value too, but again it is not
too much to do with stateless motivation.
Cheers,
Xiaohong
Best regards
Qiong Sun
"5.2. Port Utilisation Efficiency
CGN-based solutions, because they can dynamically assign
ports,
provide better IPv4 address sharing ratio than stateless
solutions
(i.e., can share the same IP address among a larger number of
customers). For Service Providers who desire an aggressive
IPv4
address sharing, a CGN-based solution is more suitable than
the
stateless.
If a Service Provider adopts an aggressive address sharing
ratio,
it is likely to be attempted by enforcing a NAT port
overloading
mode and as a consequence some applications will break.
However, as more and more hosts become dual-stack enabled,
the need
for ports in IPv4 is likely to decrease. The insurance to
have the
full set of 64K ports per host will be one of the incentives
to have
them IPv6 capable. Moreover, Service Providers should
offload some
services to IPv6 (e.g., DNS, VoIP)."
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