Re: [Idr] draft-ietf-idr-segment-routing-te-policy Policy Name Sub-TLV considerations

Hi Ketan,

> From: Idr [mailto:idr-bounces@ietf.org] On Behalf Of Ketan Talaulikar (ketant)
> 
> Hi Jeff,
> 
> I agree with you about the limits on the policy name size. 
> 
> I am not aware of any IETF standard that mandates the use of UTF-8 for encoding of string for names. 

FYI, I've just noticed the following

"All user-visible text fields must be internationalizable. See [RFC 2277] (Alvestrand, H., "IETF Policy on Character Sets and Languages," January 1998.). 
For most cases, this means UTF-8 [RFC 3629] (Yergeau, F., "UTF-8, a transformation format of ISO 10646," November 2003.)."
https://www.ietf.org/standards/ids/checklist/

> The similar object in PCEP is encoded in ASCII - https://tools.ietf.org/html/rfc8231#section-7.3.2

Ah... 

Good luck!

--Bruno

> Thanks,
> Ketan
> 
> -----Original Message-----
> From: Jeffrey Haas <jhaas@pfrc.org> 
> Sent: 12 February 2020 15:17
> To: draft-ietf-idr-segment-routing-te-policy@ietf.org; idr@ietf.org
> Subject: draft-ietf-idr-segment-routing-te-policy Policy Name Sub-TLV considerations
> 
> Authors,
> 
> In draft-ietf-idr-segment-routing-te-policy-08, Section 2.4.6 we have a TLV for Policy Name.  Its text is:
> 
> : 2.4.6.  Policy Name Sub-TLV
> : 
> :    An operator MAY set the Policy Name sub-TLV to attach a symbolic name
> :    to the SR Policy candidate path.
> : 
> :    Usage of Policy Name sub-TLV is described in section 2 in
> :    [I-D.ietf-spring-segment-routing-policy].
> : 
> :    The Policy Name sub-TLV may exceed 255 bytes length due to long
> :    policy name.  Therefore a 2-octet length is required.  According to
> :    [I-D.ietf-idr-tunnel-encaps], the first bit of the sub-TLV codepoint
> :    defines the size of the length field.  Therefore, for the Policy Name
> :    sub-TLV a code point of 128 or higher is used.
> : 
> :    The Policy Name sub-TLV is optional and it MUST NOT appear more than
> :    once in the SR Policy TLV.
> : 
> :    The Policy Name sub-TLV has following format:
> : 
> :    0                   1                   2                   3
> :     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> :    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> :    |     Type      |   Length                      |   RESERVED    |
> :    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> :    //                        Policy Name                          //
> :    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> : 
> :    Where:
> : 
> :       Type: 129.
> : 
> :       Length: Variable.
> : 
> :       RESERVED: 1 octet of reserved bits.  SHOULD be set to zero on
> :       transmission and MUST be ignored on receipt.
> : 
> :       Policy Name: Symbolic name for the policy.  It SHOULD be a string
> :       of printable ASCII characters, without a NULL terminator.
> 
> draft-ietf-spring-segment-routing-policy-06, Section 2.1 discusses this
> Sub-TLV:
> 
> :    An implementation MAY allow assignment of a symbolic name comprising
> :    of printable ASCII characters to an SR Policy to serve as a user-
> :    friendly attribute for debug and troubleshooting purposes.  Such
> :    symbolic names may identify an SR Policy when the naming scheme
> :    ensures uniqueness.
> 
> There are two observations I'd like to make:
> 1. A 65K length isn't very likely in BGP. :-)  I suggest that greater guidance for shorter names should be offered. For example, perhaps limit the length to 1K.  Alternatively, offer advice such as: "Implementations may choose to truncate long Policy Names".
> 
> 2. The guidance about "printable ASCII" is rather old-style and likely to run askance of IESG review for internationalization considerations.  I'd suggest that the field be encoded in UTF-8 and make reference to print-safety similar to RFC 8203 (BGP Administrative Shutdown) in its Security Considerations.
> 
> -- Jeff
> 
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