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Re: [ANCP] question regarding Labels in ANCP port up messages
Hi Sanjay and All,
I was reading the current ancp protocol draft in order to understand which should be the correct format for the label field in the ancp port Up message.
Actually as it was already pointed out in the alias the draft in section 5.4.2 says "GSMP Event message with PORT UP message type (80) is used" thus I am assuming that the label in the port UP message should follow the message format defined in RFC 3292, section 3.1.3:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|S|x|x| Label Type | Label Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Label Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
but from what I have seen different implementations use different format for label field: in particular several implementations use a label format that is similar to the one specified in the expired draft draft-ietf-gsmp-v3-base-spec:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|S|x|x|x|x|x|x|x|x|x|x|x|x|x|x| Label Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label Adaptation | Label Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Label Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Even if ancp does not care about the label field, having this field somehow not clearly specified in the current ancp draft can easily lead to interoperability issues, thus I think it would be very helpful if you and/or the other editors can clarify what should be the correct format for the label field to be used in the ancp Port Up message.
Thanks and best regards,
Roberta
________________________________________
From: Philippe Champagne (pchamp) [pchamp at cisco.com]
Sent: Thursday, April 24, 2008 7:14 PM
To: Sanjay Wadhwa
Cc: Maglione Roberta; Wojciech Dec (wdec); ancp at ietf.org
Subject: question regarding Labels in ANCP port up messages
Hi Sanjay
In section 5.4.2 of the draft, we have:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vers | Sub | Message Type | Result| Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Partition ID | Transaction Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|I| SubMessage Number | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Port Session Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Event Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|S|x|x| |
+-+-+-+-+ Label |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|x|x|x|x|x|x|x| Message Type | Tech Type | Block Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Extension Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where Label I suppose is taken from the RFC 3292, section 3.1.3: (well, I'm guessing)
A summary of TLV labels supported in this version of the protocol is
listed below:
TLV Label Type Section Title
--------- ---- -------------
ATM Label 0x100 ATM TLV Labels
FR Label 0x101 Frame Relay TLV Labels
MPLS Gen Label 0x102 MPLS Generic TLV Labels
FEC Label 0x103 FEC TLV Labels
All Labels will be designated as follow:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|x|S|x|x| Label Type | Label Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Label Value ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
x: Reserved Flags.
These are generally used by specific messages and will be
defined in those messages.
S: Stacked Label Indicator
Label Stacking is discussed below in section 3.1.3.5
Label Type
A 12-bit field indicating the type of label.
Label Length
A 16-bit field indicating the length of the Label Value field
in bytes.
Label Value
A variable length field that is an integer number of 32 bit
words long. The Label Value field is interpreted according to
the Label Type as described in the following sections.
The draft is a bit obscure about this and since it doesn't specify much, it can lead to misinterpretation for the unused part. Moreover, it would appear that several implementations currently use another format for the label field. Can you explain? I mean, how come what's in the current draft doesn't match what's known to be implemented?
I'm still wondering why we carried over pieces from GSMP that we do not intend to use.
I would recommend that if we are to keep them but not use them, we should mention precisely how we intend not to use them: that is how many 0 filled bytes this is expected to use
The rfc 3292 doesn't cover the case where this field is not used.
Can you shed some ligths on this?
Thanks
Regards
Phil
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