Re: [bess] Encoding a 20 bit label in a 24 bit field.

"Tapraj Singh (tapsingh)" <tapsingh@cisco.com> Tue, 16 October 2018 13:26 UTC

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From: "Tapraj Singh (tapsingh)" <tapsingh@cisco.com>
To: John E Drake <jdrake@juniper.net>, Zhuangshunwan <zhuangshunwan@huawei.com>, "Jakob Heitz (jheitz)" <jheitz@cisco.com>, BESS <bess@ietf.org>
Thread-Topic: [bess] Encoding a 20 bit label in a 24 bit field.
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Date: Tue, 16 Oct 2018 13:26:52 +0000
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Subject: Re: [bess] Encoding a 20 bit label in a 24 bit field.
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Hi 
 Agree with John's suggestion here.

Thanks
Tapraj

On 10/16/18, 5:28 AM, "BESS on behalf of John E Drake" <bess-bounces@ietf.org on behalf of jdrake@juniper.net> wrote:

    I don't think that's a good idea because depending upon their position in the stack, these labels may not be at the bottom of the stack.
    
    Yours Irrespectively,
    
    John
    
    > -----Original Message-----
    > From: BESS <bess-bounces@ietf.org> On Behalf Of Zhuangshunwan
    > Sent: Monday, October 15, 2018 9:02 PM
    > To: Jakob Heitz (jheitz) <jheitz@cisco.com>; BESS <bess@ietf.org>
    > Subject: Re: [bess] Encoding a 20 bit label in a 24 bit field.
    > 
    > It is good to make this explicit. This ambiguity has led to some unnecessary
    > interworking problems.
    > 
    > Should we also need to explicitly define the "bottom of stack" bit in the low-
    > order bit of the 3-octet label field?
    > 
    > Thanks,
    > Shunwan
    > 
    > -----Original Message-----
    > From: BESS [mailto:bess-bounces@ietf.org] On Behalf Of Jakob Heitz (jheitz)
    > Sent: Tuesday, October 16, 2018 4:21 AM
    > To: BESS <bess@ietf.org>
    > Subject: [bess] Encoding a 20 bit label in a 24 bit field.
    > 
    > We have proposed the following erratum for RFC 7432.
    > 
    > Opinions?
    > 
    > Regards,
    > Jakob.
    > 
    > 
    > -----Original Message-----
    > From: RFC Errata System <rfc-editor@rfc-editor.org>
    > Sent: Friday, October 12, 2018 12:37 PM
    > To: Ali Sajassi (sajassi) <sajassi@cisco.com>; raggarwa_1@yahoo.com;
    > nabil.n.bitar@verizon.com; aisaac71@bloomberg.net; uttaro@att.com;
    > jdrake@juniper.net; wim.henderickx@alcatel-lucent.com; db3546@att.com;
    > aretana.ietf@gmail.com; martin.vigoureux@nokia.com; Giles Heron
    > (giheron) <giheron@cisco.com>; nabil.n.bitar@verizon.com
    > Cc: Krishnamoorthy Arumugham (karumugh) <karumugh@cisco.com>;
    > l2vpn@ietf.org; rfc-editor@rfc-editor.org
    > Subject: [Technical Errata Reported] RFC7432 (5523)
    > 
    > The following errata report has been submitted for RFC7432, "BGP MPLS-
    > Based Ethernet VPN".
    > 
    > --------------------------------------
    > You may review the report below and at:
    > https://urldefense.proofpoint.com/v2/url?u=http-3A__www.rfc-
    > 2Deditor.org_errata_eid5523&d=DwICAg&c=HAkYuh63rsuhr6Scbfh0UjBXeM
    > K-ndb3voDTXcWzoCI&r=CRB2tJiQePk0cT-h5LGhEWH-
    > s_xXXup3HzvBSMRj5VE&m=IvOdDW_zoH5heXCCcs7ke0vmlQ0Hm1yCi17llZn
    > BdsY&s=n_iX5KAK2InG-bgMnZHO3o4PH9UZmYKVtes9H7-vA1E&e=
    > 
    > --------------------------------------
    > Type: Technical
    > Reported by: Krishnamoorthy Arumugham <karumugh@cisco.com>
    > 
    > Section: 7
    > 
    > Original Text
    > -------------
    > Clarifications to following sub-sections:
    > Section 7.1
    > Section 7.2
    > Section 7.5
    > 
    > 
    > Corrected Text
    > --------------
    > Section 7.1:
    > Add below text to the section 7.1 regarding the encoding of MPLS label:
    > 
    > "The value of the 20-bit MPLS label is encoded in the high-order 20 bits of the
    > 3 bytes MPLS Label field."
    > 
    > Section 7.2:
    > Add below text to the section 7.2 regarding the encoding of both the MPLS
    > label fields:
    > 
    > "The value of the 20-bit MPLS label is encoded in the high-order 20 bits of the
    > 3 bytes MPLS Label field for both MPLS Label1 and MPLS Label2."
    > 
    > Section 7.5:
    > Add below text to the section 7.5 regarding the encoding of ESI Label fields:
    > 
    > "The value of the 20-bit MPLS label is encoded in the high-order 20 bits of the
    > ESI Label field."
    > 
    > 
    > Notes
    > -----
    > MPLS label is a 20-bit value and is stored in a 3 bytes field in a packet. The 20-
    > bit MPLS label value is generally stored in higher order 20 bits of the 3 byte
    > label field. The exact encoding to be followed for storing MPLS label values
    > are not explicitly mentioned in the RFC 7432 under section 7.1, 7.2 and 7.5
    > for different types of EVPN routes. This lead to ambiguity in different
    > implementations. Hence a clarification is required.
    > 
    > Instructions:
    > -------------
    > This erratum is currently posted as "Reported". If necessary, please use
    > "Reply All" to discuss whether it should be verified or rejected. When a
    > decision is reached, the verifying party can log in to change the status and
    > edit the report, if necessary.
    > 
    > --------------------------------------
    > RFC7432 (draft-ietf-l2vpn-evpn-11)
    > --------------------------------------
    > Title               : BGP MPLS-Based Ethernet VPN
    > Publication Date    : February 2015
    > Author(s)           : A. Sajassi, Ed., R. Aggarwal, N. Bitar, A. Isaac, J. Uttaro, J.
    > Drake, W. Henderickx
    > Category            : PROPOSED STANDARD
    > Source              : Layer 2 Virtual Private Networks
    > Area                : Routing
    > Stream              : IETF
    > Verifying Party     : IESG
    > 
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