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Re: [mpls] [Bier] Encapsulation first nibble

"Jeffrey (Zhaohui) Zhang" <zzhang@juniper.net> Wed, 18 March 2015 13:52 UTC

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From: "Jeffrey (Zhaohui) Zhang" <zzhang@juniper.net>
To: Xuxiaohu <xuxiaohu@huawei.com>, Antoni Przygienda <antoni.przygienda@ericsson.com>, "stbryant@cisco.com" <stbryant@cisco.com>, Eric Rosen <erosen@juniper.net>, BIER <bier@ietf.org>, IJsbrand Wijnands <ice@cisco.com>
Thread-Topic: [Bier] Encapsulation first nibble
Thread-Index: AQHQXcZsT/NTuReqcUafEPAn7P7Hmp0a0zkAgAWxRoCAAAe/AIAAZCaAgAABcACAAEuhgIABB5lw
Date: Wed, 18 Mar 2015 13:52:30 +0000
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Subject: Re: [mpls] [Bier] Encapsulation first nibble
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Xiaohu,

> Following such logic (i.e., assign a nibble value specific to the new
> encapsulation header), we would have to consider how many available nibble
> values are there which can be used for future encapsulation headers in the
> same way.

There are still quite a few values left; defining a new encapsulation is not lightly taken; adding a new IP version is not lightly taken either. Besides, there is this "reserved value 15" idea from Ice.

Coupled with the reasons that Eric gave:

> I think the proper direction is to use the MPLS entropy label, rather than to
> have each router compute the entropy based on an analysis of the next
> encapsulation header.
> 
> So I don't think BIER justifies the use of a new MPLS special purpose
> payload-protocol-identifier label.

I would think the encap-specific nibble is quite reasonable, and better than a special purpose label.

Jeffrey

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