Internet DRAFT - draft-gp-pals-seamless-vccv
draft-gp-pals-seamless-vccv
Internet Engineering Task Force V. Govindan
Internet-Draft C. Pignataro
Updates: 5885 (if approved) Cisco Systems
Intended status: Standards Track June 30, 2015
Expires: January 1, 2016
Seamless BFD for VCCV
draft-gp-pals-seamless-vccv-01
Abstract
This document extends the procedures and Connectivity Verification
(CV) types already defined for Bidirectional Forwarding Detection
(BFD) for Virtual Circuit Connectivity Verification (VCCV) to define
Seamless BFD (S-BFD) for VCCV. This document will be extended in
future to include definition of procedures for S-BFD over Tunnels.
This document extends the CV values defined in RFC5885.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 1, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. S-BFD Connectivity Verification . . . . . . . . . . . . . . . 3
2.1. Co-existence of S-BFD and BFD capabilites . . . . . . . . 4
2.2. S-BFD CV Operation . . . . . . . . . . . . . . . . . . . 4
2.2.1. S-BFD Initiator Operation . . . . . . . . . . . . . . 4
2.2.2. S-BFD Reflector Operation . . . . . . . . . . . . . . 4
2.2.2.1. S-BFD Reflector Demultiplexing . . . . . . . . . 5
2.2.2.2. S-BFD Reflector transmission of control packets . 5
2.2.2.3. S-BFD Reflector advertisement of target
discriminators using LDP . . . . . . . . . . . . 5
2.2.2.4. S-BFD Reflector advertisement of target
discriminators using L2TP . . . . . . . . . . . . 5
2.2.2.5. Provisioning of S-BFD Reflector target
discriminators . . . . . . . . . . . . . . . . . 5
2.2.2.6. Probing of S-BFD Reflector target discriminators
using alert discriminators . . . . . . . . . . . 5
2.3. S-BFD Encapsulation . . . . . . . . . . . . . . . . . . . 6
2.4. S-BFD CV Types . . . . . . . . . . . . . . . . . . . . . 6
3. Capability Selection . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV . 7
5.2. L2TPv3 CV Types for the VCCV Capability AVP . . . . . . . 8
5.3. PW Associated Channel Type . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. Contributing Authors . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Background
BFD for VCCV [RFC5885] defines the CV types for BFD using VCCV,
protocol operation and the required packet encapsulation formats.
This document extends those procedures, CV type values to enable
S-BFD [I-D.ietf-bfd-seamless-base] operation for VCCV.
The new S-BFD CV Types are PW demultiplexer-agnostic, and hence
applicable for both MPLS and Layer Two Tunneling Protocol version 3
(L2TPv3) pseudowire demultiplexers. This document concerns itself
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with the S-BFD VCCV operation over single-segment pseudowires (SS-
PWs). The scope of this document is as follows:
This specification describes procedures only for S-BFD
asynchronous mode.
S-BFD Echo mode is outside the scope of this specification.
S-BFD operation for fault detection and status signaling is
outside the scope of this specification.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. S-BFD Connectivity Verification
S-BFD protocol provides continuity check services by monitoring the
S-BFD control packets sent and received over the VCCV channel of the
PW. The term <Connectivity Verification> is used throughout this
document to be consistent with [RFC5885].
This section defines the CV types to be used for S-BFD. It also
defines the procedures for S-BFD discriminator advertisement for the
SBD reflector and the procedure for S-BFD Initiator operation.
Two CV Types are defined for S-BFD. Table 1 summarizes the S-BFD CV
Types, grouping them by encapsulation (i.e., with versus without IP/
UDP headers) for fault detection only. S-BFD for fault detection and
status signaling is outside the scope of this specification.
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+---------------------------------------+-----------+---------------+
| | Fault | Fault |
| | Detection | Detection and |
| | Only | Status |
| | | Signaling |
+---------------------------------------+-----------+---------------+
| S-BFD, IP/UDP Encapsulation (with | TBD1 | N/A |
| IP/UDP Headers) | (Note1) | |
| | | |
| S-BFD, PW-ACH Encapsulation when | TBD2 | N/A |
| using MPLS PW or L2SS Encapsulation | (Note2) | |
| when using L2TP PW (without IP/UDP | | |
| Headers) | | |
+---------------------------------------+-----------+---------------+
Table 1: Bitmask Values for BFD CV Types
Two new bits are requested from IANA to indicate S-BFD operation.
2.1. Co-existence of S-BFD and BFD capabilites
Since the CV types for S-BFD and BFD are unique, BFD and S-BFD
capabilities can be advertised concurrently.
2.2. S-BFD CV Operation
2.2.1. S-BFD Initiator Operation
The S-BFD Initiator SHOULD bootstrap S-BFD sessions after it learns
the discriminator of the remote target identifier through one or more
of the following methods:
1. Advertisements of S-BFD discriminators made through AVP/ TLVs
defined in L2TP/ LDP.
2. Provisioning of S-BFD discriminators.
3. Probing remote S-BFD discriminators through S-BFD Alert
discriminators [I-D.akiya-bfd-seamless-alert-discrim]
S-BFD Initiator operation MUST be according to the specifications in
Section 7.2 of [I-D.ietf-bfd-seamless-base].
2.2.2. S-BFD Reflector Operation
When as pseudowire signalling protocol such as LDP or L2TPv3 is in
use the S-BFD Reflector advertises its target discriminators using
that signalling protocol. When static PWs are in use the target
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discriminator of S-BFD needs to be provisioned on the S-BFD
Initiator nodes.
All point to point pseudowires are bidirectional, the S-BFD
Reflector therefore reflects the S-BFD packet back to the
Initiator using the VCCV channel of the reverse direction of the
PW on which it was received.
It is observed that the reflector has enough information to
reflect the S-BFD Async packet received by it back to the S-BFD
initiator using the fields of the L2TPv3 headers.
S-BFD Reflector operation for BFD protocol fields MUST be
according to the specifications in Section TBD of
[I-D.ietf-bfd-seamless-base].
2.2.2.1. S-BFD Reflector Demultiplexing
TBD
2.2.2.2. S-BFD Reflector transmission of control packets
The procedures of S-BFD Reflector described in
[I-D.ietf-bfd-seamless-base] apply for S-BFD using VCCV.
2.2.2.3. S-BFD Reflector advertisement of target discriminators using
LDP
TBD.
2.2.2.4. S-BFD Reflector advertisement of target discriminators using
L2TP
The S-BFD Reflector MUST use the AVP
[I-D.gp-l2tpext-sbfd-discriminator] defined for advertising its
target discriminators using L2TP.
2.2.2.5. Provisioning of S-BFD Reflector target discriminators
S-BFD target discriminators MAY be provisioned when static PWs are
used.
2.2.2.6. Probing of S-BFD Reflector target discriminators using alert
discriminators
S-BFD alert discriminators MAY be used to probe S-BFD target
discriminators. If a node implements S-BFD reflector, it SHOULD
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respond to Alert discriminator requests received from potential S-BFD
Initiators.
2.3. S-BFD Encapsulation
Unless specified differently below, the encapsulation of S-BFD
packets is the identical the method specified in Sec.3.2 [RFC5885]
and in [RFC5880] for the encapsulation of BFD packets.
o IP/UDP BFD Encapsulation (BFD with IP/UDP Headers)
* The destination UDP port for the IP encapsulated S-BFD packet
MUST be 7784 [I-D.ietf-bfd-seamless-base].
* The encapsulation of the S-BFD header fields MUST be according
to Sec.7.2.2 of [I-D.ietf-bfd-seamless-base].
o PW-ACH/ L2SS BFD Encapsulation (BFD without IP/UDP Headers)
* The encapsulation of S-BFD packets using this format MUST be
according to Sec.3.2 of [RFC5885] with the exception of the PW-
ACH/ L2SS type.
* When VCCV carries PW-ACH/ L2SS-encapsulated S-BFD (i.e., "raw"
S-BFD), the PW-ACH (pseudowire CW's) or L2SS' Channel Type MUST
be set to TBD2 to indicate "S-BFD Control, PW-ACH/ L2SS-
encapsulated" (i.e., S-BFD without IP/UDP headers; see
Section 5.3). This is to allow the identification of the
encased S-BFD payload when demultiplexing the VCCV control
channel.
2.4. S-BFD CV Types
3. Capability Selection
When multiple S-BFD CV Types are advertised, and after applying the
rules in [RFC5885], the set that both ends of the pseudowire have in
common is determined. If the two ends have more than one S-BFD CV
Type in common, the following list of S-BFD CV Types is considered in
the order of the lowest list number CV Type to the highest list
number CV Type, and the CV Type with the lowest list number is used:
1. TBD1 - S-BFD IP/UDP-encapsulated, for PW Fault Detection only.
2. TBD2 - S-BFD PW-ACH/ L2SS-encapsulated (without IP/UDP headers),
for PW Fault Detection only.
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The order of capability selection between S-BFD and BFD is defined as
follows:
+--------------------------+-----------+-----------+----------------+
| Advertised capabilities | BFD Only | SBFD Only | Both S-BFD and |
| of PE1/ PE2 | | | BFD |
+--------------------------+-----------+-----------+----------------+
| BFD Only | BFD | None | BFD Only |
| | | (Note1) | |
| | | | |
| S-BFD Only | None | S-BFD | S-BFD only |
| | (Note1) | | |
| | | | |
| Both S-BFD and BFD | BFD only | S-BFD | Both SBFD and |
| | | only | BFD |
+--------------------------+-----------+-----------+----------------+
Table 2: Capability Selection Matrix for BFD and S-BFD
Note1: Can we mandate failing the bringup of the PW in case of a
capability mismatch?
4. Security Considerations
Security measures described in [RFC5885] and
[I-D.ietf-bfd-seamless-base] are to be followed.
5. IANA Considerations
5.1. MPLS CV Types for the VCCV Interface Parameters Sub-TLV
The VCCV Interface Parameters Sub-TLV codepoint is defined in
[RFC4446], and the VCCV CV Types registry is defined in [RFC5085].
This section lists the new BFD CV Types.
IANA has augmented the "VCCV Connectivity Verification (CV) Types"
registry in the Pseudowire Name Spaces reachable from [IANA]. These
are bitfield values. CV Type values TBD are specified in Section 2
of this document.
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MPLS Connectivity Verification (CV) Types:
Bit (Value) Description Reference
=========== =========== ==============
TBD1(0xY) S-BFD IP/UDP-encapsulated, this document
for PW Fault Detection only
TBD2(0xZ) S-BFD PW-ACH/L2SS-encapsulated, this document
for PW Fault Detection only
5.2. L2TPv3 CV Types for the VCCV Capability AVP
This section lists the new requests for S-BFD CV Types to be added to
the existing "VCCV Capability AVP" registry in the L2TP name spaces.
The Layer Two Tunneling Protocol "L2TP" Name Spaces are reachable
from [IANA]. IANA is requested to assign the following L2TPv3
Connectivity Verification (CV) Types in the VCCV Capability AVP
Values registry.
VCCV Capability AVP (Attribute Type 96) Values
----------------------------------------------
L2TPv3 Connectivity Verification (CV) Types:
Bit (Value) Description Reference
=========== =========== ==============
TBD1(0xY) S-BFD IP/UDP-encapsulated, this document
for PW Fault Detection only
TBD2(0xZ) S-BFD L2SS-encapsulated, this document
for PW Fault Detection only
5.3. PW Associated Channel Type
As per the IANA considerations in [RFC5586], IANA is requested to
allocate the following Channel Types in the "MPLS Generalized
Associated Channel (G-ACh) Types" registry:
IANA has reserved a new Pseudowire Associated Channel Type value as
follows:
Registry:
TLV
Value Description Follows Reference
------ ---------------------------------- ------- ---------------
TBD2 S-BFD Control, PW-ACH/L2SS No [This document]
encapsulation
(without IP/UDP Headers)
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6. Acknowledgements
Authors would like to thank Nobo Akiya, Stewart Bryant, Pawel
Sowinski and Greg Mirsky for providing the core inputs of this
document and for performing thorough reviews and providing number of
comments. Authors would also like to thank Yuanlong for comments
received.
7. Contributing Authors
Mallik Mudigonda
Cisco Systems
Email: mmudigon@cisco.com
8. References
8.1. Normative References
[I-D.akiya-bfd-seamless-alert-discrim]
Akiya, N., Pignataro, C., and D. Ward, "Seamless
Bidirectional Forwarding Detection (S-BFD) Alert
Discriminator", draft-akiya-bfd-seamless-alert-discrim-03
(work in progress), October 2014.
[I-D.gp-l2tpext-sbfd-discriminator]
Govindan, V. and C. Pignataro, "Advertising S-BFD
Discriminators in L2TPv3", draft-gp-l2tpext-sbfd-
discriminator-00 (work in progress), March 2015.
[I-D.ietf-bfd-seamless-base]
Akiya, N., Pignataro, C., Ward, D., Bhatia, M., and J.
Networks, "Seamless Bidirectional Forwarding Detection
(S-BFD)", draft-ietf-bfd-seamless-base-05 (work in
progress), June 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
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[RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[RFC5885] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)", RFC 5885, June 2010.
8.2. Informative References
[IANA] Internet Assigned Numbers Authority, "Protocol
Registries", <http://www.iana.org>.
Authors' Addresses
Vengada Prasad Govindan
Cisco Systems
Email: venggovi@cisco.com
Carlos Pignataro
Cisco Systems
Email: cpignata@cisco.com
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