IETF 67, Nov 2006Slide 1 VCCV Extensions for Multi- Segment Pseudo-Wire draft-hart-pwe3-segmented-pw-vccv-01.txt draft-ietf-pwe3-segmented-pw-04.txt Mustapha Aïssaoui, Alcatel Tom Nadeau, Cisco

IETF 67, Nov 2006Slide 2 Introduction Requirements –when a switching point exists between PE nodes, it is required to be able to continue operating VCCV end-to-end across a S-PE and, –to provide the ability to trace the path of the MS-PW over any number of segments Two proposed methods to achieve these objectives The first method is based on re-using the existing VCCV CW and decrementing the TTL of the PW label at each hop in the path of the MS-PW –described in draft-hart-pwe3-segmented-pw-vccv-01.txt –suitable to deployments where T-PE nodes continue to use the SS-PW control word –requires S-PE nodes capable of decrementing the TTL field for all PW packets The second method is based on using a new MH-VCCV control word and decrementing the TTL field in the control word –described in draft-ietf-pwe3-segmented-pw-03.txt –suitable to deployments where S-PE nodes cannot rely the TTL in the PW label to identify if a VCCV packet is destined to this node or not –requires upgrade to T-PE and S-PE user and control plane to use the new MH- VCCV CW

IETF 67, Nov 2006Slide 3 Proposal to Move Forward Authors believe both methods are required based on existing deployments Initial text describing both methods added to draft- ietf-pwe3-segmented-pw-04.txt –Will be published shortly Both methods will provide the following capabilities –End-to-end VCCV (ping mode) –Partial tracing from T-PE (ping mode) –Partial Tracing between S-PE’s (ping mode) –Automated VCCV Trace from T-PE (trace mode)

IETF 67, Nov 2006Slide 4 Signaling MS-PW VCCV Capability Like in SS-PW, MS-PW VCCV capabilities are signaled using the VCCV parameter included in the interface parameter field of the PW ID FEC TLV or the sub-TLV interface parameter of the Generalized PW ID FEC TLV When using the SS-PW VCCV CW method, T-PE signals CC type 1 When using the MH-VCCV CW method, T-PE signals the new CC type 4 S-PE nodes processing of the VCCV parameter removes CC Types specified by the originating T-PE, except CC Types 1 and 4 which are passed unchanged The far end T-PE, T-PE2, receives the VCCV parameter indicating that one or both Control Word CC types only if they are supported by the sending T-PE (T-PE1) and all S-PE’s along the MS-PW path If T-PE1 signaled both types and T-PE2 also supports them, T-PE2 uses the SS-PW CW CC type in preference

IETF 67, Nov 2006Slide 5 New VCCV Control Channel Type 4 The new MH-VCCV CW requires a new CC Type | 0x0c | 0x04 | CC Types | CV Types | x01 Type 1: PWE3 control word with 0001 as first nibble 0x02 Type 2: MPLS Router Alert Label. 0x04 Type 3: MPLS PW Demultiplexor Label TTL = 1 (Type 3). 0x08 Type 4: MH-VCCV Control Word

IETF 67, Nov 2006Slide 6 Packet Encapsulation with MH- VCCV CW A new PW associated channel type is defined to distinguish VCCV packets with new MH-VCCV CW from existing VCCV CW | | 0x00 | Reserved = 0 | Channel Type = TBD | | MH-TTL | MH-VCCV sub-TLV | Three new values are required –One for IPv4 control channel –One for IPv6 control channel –One for BFD packets without IP/UDP headers

IETF 67, Nov 2006Slide 7 Control Plane Processing of an MS- PW VCCV Echo Message Native | | Native Service | | Service (AC) | | | | | | (AC) | V V V V V V | | | | |T-PE1|=========|S-PE1|=========|T-PE2| | | | |......PW1-Seg |.PW1-Seg | | | | CE1| | |=========| |=========| | | CE2| | | | |

IETF 67, Nov 2006Slide 8 Ping Mode of Operation Single operation to check MS-PW FEC at an S-PE or destination T-PE Sending a VCCV Echo Request Message –The sender of the echo request message requires the FEC of the last segment to the target S-PE/T-PE node –This information can be configured manually or can be obtained by inspecting the corresponding sub-TLV's of the PW switching point TLV Receiving a VCCV Echo Request Message –Target node validates the request and responds with a VCCV echo reply –If target node is an S-PE for the MS-PW, it responds with an echo reply containing a FEC TLV with the FEC of the next downstream segment and a return code of 8 (label switched at stack-depth) –If target node is the egress T-PE of the MS-PW, it responds with an echo reply with a return code of 3 (egress router) and no FEC TLV is included Receiving a VCCV Echo Reply Message –The sender node may choose to ignore the information in the FEC TLV in the echo reply and report only the return code to the operator

IETF 67, Nov 2006Slide 9 Trace Mode of Operation Automated path tracing capability that iteratively probes the segments the MS-PW to learn the target FEC information Sending a VCCV Echo Request Message –The sender of the echo request message (T-PE) learns the target FEC by probing one by one the hops of the MS-PW path Receiving a VCCV Echo Request Message –Same as in ping mode Receiving a VCCV Echo Reply Message –the node builds the subsequent VCCV echo request message by incrementing TTL field in PW label or in MH-VCCV CW and using the downstream FEC it received in the echo request message –It sends the echo request message to the next downstream PW segment

IETF 67, Nov 2006Slide 10 Next Step Add details of control plane processing and automated trace into draft-ietf-pwe3- segmented-pw-04.txt Authors would like to request WG feedback on mailing list