[Softwires] ds-lite tunnel option

[Tomasz Mrugalski <tomasz.mrugalski at googlemail.com>]

Hi,

From what I understood during today's meeting discussion, there are 2 goals that we are trying to achieve:

- Standarized option is urgently needed, so we should not prolong the discussion more than necessary

- Generic purpose tunneling and encapsulation approach was discussed before without any noticeable agreements

We have basically 2 proposals (Another proposed option mentioned in draft-townsley-ipv6-rd6-00 is designed for DHCPv4, thus not applicable for this discussion):

1. Dual-Stack Lite option, proposed in draft-dhankings-softwire-tunnel-option-03. This is a simple solution, designed specifically for addressing dual-stack lite tunnel configuration (IPv4-over-IPv6). There are 2 independent implementations of that proposal available (ISC and dibbler, both open source).
2. SC Discovery option, proposed in draft-guo-softwire-sc-discovery-01. The second proposal attempts to address generic tunnel configuration, over IPv4 and IPv6 as well. Two options (one for DHCPv4 and one for DHCPv6). Its generic approach comes at a cost. With 3 different fields for type specification and preference, the total number of fields is 7, plus additional possible sub options. Although 3 type fields (SC type, Tunnel Type and Protocol Type) give great flexibility, significant part of all possible combinanations is irrelevent or plain wrong. Therefore number of actual legal combinations is quite limited. Also, there is no implementation.
   

There is also certain confusion regarding the sc-discovery draft. -00 was presented during meeting, but there is -01 version available. The only noticeable change is Protocol Type field being extended to 16 bits and ETHER-TYPE values are used.

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Taking into consideration that there was a comment by an Internet Area Director that DHCPv4 options specification is no longer a priority, I propose to continue working on Dual-Stack Lite option, but to use some ideas from SC Discovery option. As dual-stack lite is a IPv4/IPv6 only, there is no need to specify tunnel type. Also, this will avoid confusion for vendors if there are multiple encapsulations required. No, there is just single one: IPv4/IPv6 only.

Should more generic tunneling configuration mechanism become required, additional suboptions may be defined in the future.

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What are group's thoughts regarding that matter?

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If there is a contributting co-author position available, I would be happy to volunteer.

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Regards,

Tomek