Updated text regarding Mutability in the SRH Draft

[Bob Hinden <[e-mail]>]

Hello

Ole and I spent some time reviewing the email on the list and current text in <draft-ietf-6man-segment-routing-header-19.txt>.  We would like to propose the following text in Section 2.

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OLD:

In the SRH, the Next Header, Hdr Ext Len, and Routing Type fields are
defined in Section 4.4 of [RFC8200] as not mutable.  The Segments
Left field is defined as mutable in Section 4.4 of [RFC8200].

Some of the other fields of the SRH change en route (i.e. they are
mutable).  The SRH is processed as defined in Section 4.3 of this
document, and uniquely per SID type.  The mutability of the remaining
fields in the SRH (Flags, Tag, Segment List, Optional TLVs) are
defined in that section, in the context of segment processing.

NEW:

In the SRH, the Next Header, Hdr Ext Len, and Routing Type fields are defined in Section 4.4 of [RFC8200] as not mutable.  The Segments Left field is defined as mutable in Section 4.4 of [RFC8200].

The mutability of the TLV value is defined by the most significant bit in the type, as specified in section 2.1.

Section 4.3 defines the mutability of the remaining fields in the SRH (Flags, Tag, Segment List) in the context of the SID type defined in this document.

New SIDs defined in the future MUST specify the mutability properties of the Flags, Tag, and Segment List.  Note, that in effect these fields are mutable.

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We think this should resolve the open issues regarding defining mutability in SRH.  Please let us know what you think.

Thanks,
Bob & Ole