Hi,

Here is my review of the draft.

Best regards,
Ian

Pg 5 - states a 'dual-stack' router. The AFBR is not really dual-stack here. It 
has two single stack interfaces and implements a transition technology. Suggest 
removal of dual-stack.

Section 4.1
The translation between the IPv4 and IPv6 PIM messages seems underspecified. It 
would be useful to provide some examples showing how the new addresses are used 
in the different translations into the PIM message formats (RFC7741 Section 
4.1).

Section 4.2
The term ‘MPREFIX64’ is not defined in RFC7371. As there are a number of 
different formats for multicast prefixes in RFC7371, it would be useful to 
point to the relevant section to avoid confusion.

Why was the name MPREFIX64 chosen for 4in6 multicast? In other Softwire docs 
(e.g. RFC7598), ’46’ is used to denote 4 in 6 functions and 64 for 6 in 4. As 
the addressing and mechanism for 4in6 differs for 6in4, it would make sense to 
differentiate this in the naming of the fields (i.e. use MPREFIX46, uPrefix46 
for 4in6 and uPrefix64 for 6in4).

Section 6.3
Section 6 overall defines requirements for the control plane. Sections 6.1. and 
6.2 are MUST requirements. 6.3 uses ‘should’ in defining the behaviour. Can the 
mechanism work without implementing sec 6.3 and in which situations is it 
acceptable not to?

Section 6.5
This introduces the encapsulation of messages, but doesn’t provide any 
information about what type of encapsulation is used. Figure 7 shows UDP. Is 
this part of the encapsulation? As this is necessary for the mechanism to work 
and needs to be implemented on the AFBRs, there needs to be references and 
requirements language on what needs to be implemented.

s/we do insure/it is ensured/

Section 7.2
Are there options on the kind of tunnel encapsulation that can be used? It 
would be useful to enumerate some of these and for interoperability one of them 
needs to be mandatory to implement.

References
RFC2119 Needs to have a normative reference
RFC4601 has been obsoleted by RFC7761

General - 
The document doesn’t contain the ‘Conventions/Requirements Language’ 
boilerplate pointing to RFC2119 that needs to be in a standards track document. 
(The key words "MUST", "MUST NOT”, …)

The use of RFC2119 language and the case of the words throughout the document 
is not consistent (there are a number of lower case ‘must’ etc, that probably 
should be uppercase).

The term ‘should’ (lower case) is used in a number of places that make the 
functionality of the mechanism seem uncertain (e.g. Figure 1 - 'Multicast 
packets should get across the I-IP transit core'. Sec 4.1 'it should be 
translated back’).

There are some points that would seem to need MUST requirements that are 
missing - e.g. Section 4.4 'every uPrefix64 that AFBR announces should be 
different either, and uniquely identifies each AFBR’. If two AFBRs are 
announcing the same uPrefix64, surely there will be problems.

Suggest that the use of RFC2119 language is revised throughout the document to 
avoid these problems and to tighten up the specification as a whole.

The document needs the language and grammar checking throughout.


> On 7 Apr 2016, at 16:58, Ian Farrer <ianfar...@gmx.com> wrote:
> 
> Hi,
> 
> This document has been around for some time, but has not received any 
> substantive reviews. Can I ask for volunteers who are willing to provide 
> reviews?
> 
> Thanks,
> Ian
> 
> 
> _______________________________________________
> Softwires mailing list
> Softwires@ietf.org
> https://www.ietf.org/mailman/listinfo/softwires

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