> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Lee, Yiu > Sent: Thursday, May 12, 2011 6:53 PM > To: Dan Wing; 'David Harrington'; 'Transport Directorate'; tsv- > [email protected] > Subject: Re: TSVDIR review, draft-ietf-softwire-dual-stack-lite-08 > > Hi Dan, > > We just released a new revision of the ds-lite draft. Did we address > all your comments?
Yes, all my comments were addressed. Thank you, -d > Thanks, > Yiu > > > > On 5/5/11 8:42 PM, "Dan Wing" <[email protected]> wrote: > > >I've reviewed this document as part of the transport area > directorate's > >ongoing effort to review key IETF documents. These comments were > written > >primarily for the transport area directors, but are copied to the > >document's > >authors for their information and to allow them to address any issues > >raised. The authors should consider this review together with any > other > >last-call comments they receive. Please always CC [email protected] if > you > >reply to or forward this review. > > > >This draft is basically ready for publication, but has nits that > should be > >fixed before publication: > > > > > >In draft-ietf-softwire-dual-stack-lite-08, it says: > > > > 8.3. Application Level Gateways (ALG) > > > > AFTR performs NAT-44 and inherits the limitations of NAT. Some > > protocols require ALGs in the NAT device to traverse through the > NAT. > > For example: SIP and ICMP require ALGs to work properly. > > > >Three comments on that "For example:" > > > >1. I do not believe SIP requires an ALG. > > > >Here are three citations that SIP ALG is unnecessary: > > * ICE (RFC5245), which has the SIP endpoint do its own NAT traversal. > >With > > this, a SIP ALG is unnecessary. > > * Session Border Controllers routinely implement 'media latching' > >(described > > in draft-ietf-mmusic-media-path-middleboxes), which works with > >endpoints > >that > > don't implement ICE. With this, a SIP ALG is unnecessary. > > * draft-ietf-sipping-nat-scenarios describes how all of this stuff > works > >in > > great detail, and its Section 3 says SIP ALG is not required. > > > >I worry that the IETF is requiring / suggesting / recommending that > >vendors > >implement ALGs in NATs. If the IETF were to make such a > recommendation, > >it > >needs to come from BEHAVE which is where the NAT work occurs, not > >SOFTWIRE. > > > >Unless there is a citation that SIP ALG is necessary, please strike > it. > > > > > >2. "ALG" is an abbreviation for Application Layer Gateway, but ICMP is > not > >an application; it is a layer 4 protocol. If anything, it is > >traditionally > >considered a "layer 3.5", because it is not normally used for > transport > >but > >rather to signal the IP layer. The term "ALG" is not appropriate when > >discussing ICMP. RFC5508, which describes the behavior of ICMP for > NAT, > >does not use the term ALG (or Application) when describing ICMP. I > >suggest > >simply striking "ICMP" from the example of protocols needing an ALG. > > > >This also requires updating the text: > > > > This specification only requires that the AFTR MUST > > support [RFC5508]. > > > >by moving it out of the ALG section and to section 8.2 ("NAT > Conformance") > >where there are already citations for RFC4787 (UDP operation) and > RFC5382 > >(TCP operation). > > > >I suggest striking the mention of RFC5508 from the ALG section and > adding > >it > >to Section 8.2 ("NAT Conformance"), like this: > > > >OLD: > > A dual-stack lite AFTR MUST implement behavior conforming to the > best > > current practice, currently documented in [RFC4787] and [RFC5382]. > >NEW: > > A dual-stack lite AFTR MUST implement behavior conforming to the > best > > current practice, currently documented in [RFC4787], [RFC5382], and > >.................................................................^^^^^ > > [RFC5508]. > >...^^^^^^^^^ > > > > > >3. If the authors desire an example of a protocol that requires an > ALG, a > >good example is "active-mode FTP". (Which is seldom used anymore, > because > >it requires an ALG! It has been surpassed by passive-mode FTP.) > > > >-d > > > >
