Implementing MPLS OAM

Implementing MPLS OAM

MPLS Operations, Administration, and Maintenance (OAM) helps service providers to monitor label-switched paths (LSPs) and quickly isolate MPLS forwarding problems to assist with fault detection and troubleshooting in an MPLS network. This module describes MPLS LSP Ping and Traceroute features which can be used for failure detection and troubleshooting of MPLS networks.

MPLS LSP Ping

The MPLS LSP Ping feature is used to check the connectivity between Ingress LSR and egress LSRs along an LSP. MPLS LSP ping uses MPLS echo request and reply messages, similar to Internet Control Message Protocol (ICMP) echo request and reply messages, to validate an LSP. While ICMP echo request and reply messages validate IP networks, MPLS echo and reply messages validate MPLS networks. The MPLS echo request packet is sent to a target router through the use of the appropriate label stack associated with the LSP to be validated. Use of the label stack causes the packet to be forwarded over the LSP itself. The destination IP address of the MPLS echo request packet is different from the address used to select the label stack. The destination IP address is defined as a 127.x.y.z/8 address and it prevents the IP packet from being IP switched to its destination, if the LSP is broken.

An MPLS echo reply is sent in response to an MPLS echo request. The reply is sent as an IP packet and it is forwarded using IP, MPLS, or a combination of both types of switching. The source address of the MPLS echo reply packet is an address obtained from the router generating the echo reply. The destination address is the source address of the router that originated the MPLS echo request packet. The MPLS echo reply destination port is set to the echo request source port.

The following figure shows MPLS LSP ping echo request and echo reply paths.

Figure 1. MPLS LSP Ping Echo Request and Reply Paths

By default, the ping mpls ipv4 command tries to determine the Forwarding Equivalence Class (FEC) being used automatically. However, this is only applicable at head-end and works only if the FEC at the destination is same as the source. If the source and destination FEC types are not the same, the ping mpls ipv4 command may fail to identify the targeted FEC type. You can overcome this limitation by specifying the FEC type in MPLS LSP ping using the fec-type command option. If the user is not sure about the FEC type at the transit or the destination, or it may change through network, use of the generic FEC type command option is recommended. Generic FEC is not coupled to a particular control plane and allows path verification when the advertising protocol is unknown, or may change during the path of the echo request. If you are aware of the destination FEC type, specify the target FEC as BGP or LDP.

Configuration Examples

This example shows how to use MPLS LSP ping to test the connectivity of an IPv4 LDP LSP. The destination is specified as a Label Distribution Protocol (LDP) IPv4 address.

RP/0/RSP0/CPU0:router# ping mpls ipv4 10.1.1.2/32 verbose

Sun Nov 15 11:27:43.070 UTC

Sending 5, 100-byte MPLS Echos to 10.1.1.2/32,
      timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface,
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
  'P' - no rx intf label prot, 'p' - premature termination of LSP,
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!      size 100, reply addr 10.1.0.2, return code 3
!      size 100, reply addr 10.1.0.2, return code 3
!      size 100, reply addr 10.1.0.2, return code 3
!      size 100, reply addr 10.1.0.2, return code 3
!      size 100, reply addr 10.1.0.2, return code 3

Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/4 ms

In this example, the destination is specified as a Label Distribution Protocol (LDP) IPv4 prefix and Forwarding Equivalence Class (FEC) type is specified as generic.

RP/0/RSP0/CPU0:router# ping mpls ipv4 10.1.1.2/32 fec-type generic

Wed Nov 25 03:36:33.143 UTC
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32,
      timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface,
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
  'P' - no rx intf label prot, 'p' - premature termination of LSP,
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms

In this example, the destination is specified as a Label Distribution Protocol (LDP) IPv4 prefix and the FEC type is specified as BGP.

RP/0/RSP0/CPU0:router# ping mpls ipv4 10.1.1.2/32 fec-type bgp

Wed Nov 25 03:38:33.143 UTC
Sending 5, 100-byte MPLS Echos to 10.1.1.2/32,
      timeout is 2 seconds, send interval is 0 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface,
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
  'P' - no rx intf label prot, 'p' - premature termination of LSP,
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/2/3 ms

MPLS LSP Traceroute

The MPLS LSP Traceroute feature is used to isolate the failure point of an LSP. It is used for hop-by-hop fault localization and path tracing. The MPLS LSP Traceroute feature relies on the expiration of the Time to Live (TTL) value of the packet that carries the echo request. When the MPLS echo request message hits a transit node, it checks the TTL value and if it is expired, the packet is passed to the control plane, else the message is forwarded. If the echo message is passed to the control plane, a reply message is generated based on the contents of the request message.

The following figure shows an MPLS LSP traceroute example with an LSP from LSR1 to LSR4.

Figure 2. MPLS LSP Traceroute

By default, the traceroute mpls ipv4 command tries to determine the Forwarding Equivalence Class (FEC) being used automatically. However, this is only applicable at head-end and works only if the FEC at the destination is same as the source. If the source and destination FEC types are not the same, the traceroute mpls ipv4 command may fail to identify the targeted FEC type. You can overcome this limitation by specifying the FEC type in MPLS LSP traceroute using the fec-type command option. If the user is not sure about the FEC type at the transit or the destination, or it may change through network, use of the generic FEC type command option is recommended. Generic FEC is not coupled to a particular control plane and allows path verification when the advertising protocol is unknown, or may change during the path of the echo request. If you are aware of the destination FEC type, specify the target FEC as BGP or LDP.

Configuration Examples

This example shows how to use the traceroute command to trace to a destination.

RP/0/RSP0/CPU0:router# traceroute mpls ipv4 10.1.1.2/32 destination 127.0.0.3 127.0.0.6 2
Sat Jan 27 03:50:23.746 UTC

Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface,
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
  'P' - no rx intf label prot, 'p' - premature termination of LSP,
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

Destination address 127.0.0.3
  0 10.2.1.2 MRU 1500 [Labels: 24000 Exp: 0]
L 1 10.2.1.1 MRU 1500 [Labels: implicit-null Exp: 0] 8 ms
! 2 10.1.0.2 3 ms

Destination address 127.0.0.5
  0 10.2.1.2 MRU 1500 [Labels: 24000 Exp: 0]
L 1 10.2.1.1 MRU 1500 [Labels: implicit-null Exp: 0] 5 ms
! 2 10.1.0.2 2 ms


This example shows how to use the traceroute command and how to specify the maximum number of hops for the traceroute to traverse by specifying the ttl value.

RP/0/RSP0/CPU0:router# traceroute mpls ipv4 10.1.1.2/32 ttl 1
Sun Nov 15 12:20:14.145 UTC
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface,
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
  'P' - no rx intf label prot, 'p' - premature termination of LSP,
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0

Type escape sequence to abort.

  0 10.1.0.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.1.0.2 3 ms

This example shows how to use the traceroute command to trace to a destination and FEC type is specified as generic.

RP/0/RSP0/CPU0:router# traceroute mpls ipv4 10.1.1.2/32 fec-type generic
Sun Nov 15 12:25:14.145 UTC
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 2 ms

This example shows how to use the traceroute command to trace to a destination and FEC type is specified as BGP.

RP/0/RSP0/CPU0:router# traceroute mpls ipv4 10.1.1.2/32 fec-type bgp
Sun Nov 15 12:25:14.145 UTC
Tracing MPLS Label Switched Path to 10.1.1.2/32, timeout is 2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
'L' - labeled output interface, 'B' - unlabeled output interface,
'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label,
'P' - no rx intf label prot, 'p' - premature termination of LSP,
'R' - transit router, 'I' - unknown upstream index,
'X' - unknown return code, 'x' - return code 0
Type escape sequence to abort.
0 10.12.12.1 MRU 1500 [Labels: implicit-null Exp: 0]
! 1 10.12.12.2 2 ms

Overview of P2MP TE Network

A Point to Multipoint (P2MP) TE network contains the following elements:

  • Headend Router

    The headend router, also called the source or ingress router, is responsible for initiating the signaling messages that set up the P2MP TE LSP. The headend router can also be a branch point, which means the router performs packet replication and the sub-LSPs split into different directions.

  • Midpoint Router

    The midpoint router is where the sub-LSP signaling is processed. The midpoint router can be a branch point.

  • Tailend Router

    The tailend router, also called the destination, egress, or leaf-node router, is where sub-LSP signaling ends. The router which is one of potentially many destinations of the P2MP TE LSP.

  • Bud Router

    A bud router is a midpoint and tailend router at the same time. An LSR that is an egress LSR, but also has one or more directly connected downstream LSRs.

  • Branch Router

    A branch router is either a midpoint or tailend router at any given time.

  • Transit Router

    A transit router is an LSR that is not an egress router, but also has one or more directly connected downstream routers.

  • A P2MP tunnel consists of one or more sub-LSPs.All sub-LSPs belonging to the same P2MP tunnel employ the same constraints, protection policies, and so on, which are configured at the headend router.

Elements of P2MP TE Network illustrates the elements of P2MP TE network.

Figure 3. Elements of P2MP TE Network
Elements of P2MP TE

P2MP TE tunnels build on the features that exist in basic point-to-point TE tunnels. The P2MP TE tunnels have the following characteristics:

  • There is one source (headend) but more than one destination (tailend).

  • They are unidirectional.

  • They are explicitly routed.

  • Multiple sub-LSPs connect the headend router to various tailend routers.

P2MP Ping

The P2MP ping feature is used to check the connectivity between Ingress LSR and egress LSR, along a P2MP LSP. The Ingress LSR sends the P2MP echo request message along the specified P2MP LSP. All egress LSRs which receive the P2MP echo request message from the ingress LSR must send a P2MP echo reply message to the ingress LSR, according to the reply mode specified in the P2MP echo request message.

P2MP Traceroute

The P2MP traceroute feature is used to isolate the failure point of a P2MP LSP.

Traceroute can be applied to all nodes in the P2MP tree. However, you can select a specific traceroute target through the P2MP Responder Identifier TLV. An entry in this TLV represents an responder-id or a transit node. This is only the case for P2MP TE LSPs.


Note


Only P2MP TE LSP IPv4 is supported. If the Responder Identifier TLV is missing, the echo request requests information from all responder-ids.


MPLS OAM Support for BGP 3107

The MPLS OAM Support for BGP 3107 feature provides support for ping, traceroute and treetrace (traceroute multipath) operations for LSPs signaled via BGP for the IPv4 unicast prefix FECs in the default VRF, according to the RFC 3107 - Carrying Label Information in BGP-4. This feature adds support for MPLS OAM operations in the seamless MPLS architecture deployments, i.e., combinations of BGP and LDP signaled LSPs.

For more information about ping and traceroute, see Implementing MPLS OAM chapter in the MPLS Configuration Guide for Cisco ASR 9000 Series Routers. For more information about ping and traceroute commands, see MPLS OAM Commands chapter in the MPLS Command Reference for Cisco ASR 9000 Series Routers.

IP-Less MPLS-TP Ping and MPLS-TP Traceroute

According to RFC-6426, IP-Less MPLS-TP ping and MPLS-TP traceroute with the ACH header, if a node receives an MPLS-TP ping or traceroute request packet over ACH, without IP or UDP headers, the node drops the echo request packet and does not send a response when:
  • the reply mode is 4

  • the node does not have a return MPLS LSP path to the echo request source.

If a node receives an MPLS echo request with a reply mode other than 4 (i.e., reply via application-level control channel), the node responds to using that reply mode. If the node does not support the reply mode requested, or is unable to reply using the requested reply mode in any specific instance, the node drops the echo request packet and does not send a response.

For more information about ping and traceroute, see Implementing MPLS OAM chapter in the MPLS Configuration Guide for Cisco ASR 9000 Series Routers. For more information about ping and traceroute commands, see MPLS OAM Commands chapter in the MPLS Command Reference for Cisco ASR 9000 Series Routers.

Configuration Examples: P2MP Ping and P2MP Traceroute

This example shows an extract of the P2MP ping command.

RP/0/RSP0/CPU0:router# ping mpls traffic-eng tunnel-mte 10
Sending 1, 100-byte MPLS Echos to tunnel-mte10,
      timeout is 2.2 seconds, send interval is 0 msec, jitter value is 200 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

Request #1
! reply addr 192.168.222.2
! reply addr 192.168.140.2
! reply addr 192.168.170.1

Success rate is 100 percent (3 received replies/3 expected replies),
     round-trip min/avg/max = 154/232/302 ms

This example shows an extract of the P2MP ping command with the jitter option.



RP/0/RSP0/CPU0:router# ping mpls traffic-eng tunnel-mte 10 jitter 300

Sending 1, 100-byte MPLS Echos to tunnel-mte10,
      timeout is 2.3 seconds, send interval is 0 msec, jitter value is 300 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

Request #1
! reply addr 192.168.222.2
! reply addr 192.168.140.2
! reply addr 192.168.170.1

Success rate is 100 percent (3 received replies/3 expected replies),
     round-trip min/avg/max = 148/191/256 ms

This example shows an extract of the P2MP ping command with the ddmap option.



RP/0/RSP0/CPU0:router# ping mpls traffic-eng tunnel-mte 10 ddmap 

Sending 1, 100-byte MPLS Echos to tunnel-mte10,
      timeout is 2.2 seconds, send interval is 0 msec, jitter value is 200 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

Request #1
! reply addr 192.168.222.2
! reply addr 192.168.140.2
! reply addr 192.168.170.1

Success rate is 100 percent (3 received replies/3 expected replies),
     round-trip min/avg/max = 105/178/237 ms


RP/0/RSP0/CPU0:router# show mpls traffic-eng tunnels p2mp 10
Mon Apr 12 12:13:55.075 EST
Signalling Summary:
              LSP Tunnels Process:  running
                     RSVP Process:  running
                       Forwarding:  enabled
          Periodic reoptimization:  every 3600 seconds, next in 654 seconds
           Periodic FRR Promotion:  every 300 seconds, next in 70 seconds
          Auto-bw enabled tunnels:  0 (disabled)

Name: tunnel-mte10
   Status:
     Admin: up  Oper: up (Up for 12w4d)

     Config Parameters:
      Bandwidth: 0 kbps (CT0) Priority: 7 7 Affinity: 0x0/0xffff
      Metric Type: TE (default)
      Fast Reroute: Not Enabled, Protection Desired: None
      Record Route: Not Enabled

      Destination summary: (3 up, 0 down, 0 disabled) Affinity: 0x0/0xffff
      Auto-bw: disabled
      Destination: 10.1.0.1
        State: Up for 12w4d
        Path options:
          path-option 1 dynamic     [active]
      Destination: 10.2.0.1
        State: Up for 12w4d
        Path options:
          path-option 1 dynamic     [active]
      Destination: 10.3.0.1
        State: Up for 12w4d
        Path options:
          path-option 1 dynamic     [active]

     History:
       Reopt. LSP:
         Last Failure:
           LSP not signalled, identical to the [CURRENT] LSP
           Date/Time: Thu Jan 14 02:49:22 EST 2010 [12w4d ago]

    Current LSP:
      lsp-id: 10002 p2mp-id: 10 tun-id: 10 src: 10.0.0.1 extid: 10.0.0.1
      LSP up for: 12w4d
      Reroute Pending: No
      Inuse Bandwidth: 0 kbps (CT0)
      Number of S2Ls: 3 connected, 0 signaling proceeding, 0 down

      S2L Sub LSP: Destination 10.1.0.1 Signaling Status: connected
        S2L up for: 12w4d
        Sub Group ID: 1 Sub Group Originator ID: 10.1.0.1
        Path option path-option 1 dynamic    (path weight 1)
        Path info (OSPF 1 area 0)
          192.168.222.2
          10.1.0.1

      S2L Sub LSP: Destination 10.2.0.1 Signaling Status: connected
        S2L up for: 12w4d
        Sub Group ID: 2 Sub Group Originator ID: 10.0.0.1
        Path option path-option 1 dynamic    (path weight 2)
        Path info (OSPF 1 area 0)
          192.168.222.2
          192.168.140.3
          192.168.140.2
          10.2.0.1

      S2L Sub LSP: Destination 10.3.0.1 Signaling Status: connected
        S2L up for: 12w4d
        Sub Group ID: 3 Sub Group Originator ID: 10.0.0.1
        Path option path-option 1 dynamic    (path weight 2)
        Path info (OSPF 1 area 0)
          192.168.222.2
          192.168.170.3
          192.168.170.1
          10.3.0.1

    Reoptimized LSP (Install Timer Remaining 0 Seconds):
      None
    Cleaned LSP (Cleanup Timer Remaining 0 Seconds):
      None
Displayed 1 (of 16) heads, 0 (of 0) midpoints, 0 (of 0) tails
Displayed 1 up, 0 down, 0 recovering, 0 recovered heads

RP/0/RSP0/CPU0:router# ping mpls traffic-eng tunnel-mte 10 lsp id 10002
Mon Apr 12 12:14:04.532 EST

Sending 1, 100-byte MPLS Echos to tunnel-mte10,
      timeout is 2.2 seconds, send interval is 0 msec, jitter value is 200 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

Request #1
! reply addr 192.168.222.2
! reply addr 192.168.170.1
! reply addr 192.168.140.2

Success rate is 100 percent (3 received replies/3 expected replies),
     round-trip min/avg/max = 128/153/167 ms

This example shows an extract of the P2MP ping command with the responder-id.


RP/0/RSP0/CPU0:router# ping mpls traffic-eng tunnel-mte 10 responder-id 10.3.0.1
Mon Apr 12 12:15:34.205 EST

Sending 1, 100-byte MPLS Echos to tunnel-mte10,
      timeout is 2.2 seconds, send interval is 0 msec, jitter value is 200 msec:

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

Request #1
! reply addr 192.168.170.1

Success rate is 100 percent (1 received reply/1 expected reply),
     round-trip min/avg/max = 179/179/179 ms

This example shows an extract of the P2MP traceroute command with the ttl option.


RP/0/RSP0/CPU0:router# traceroute mpls traffic-eng tunnel-mte 10  ttl 4
Mon Apr 12 12:16:50.095 EST

Tracing MPLS MTE Label Switched Path on tunnel-mte10, timeout is 2.2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

! 1 192.168.222.2 186 ms [Estimated Role: Bud]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]

! 2 192.168.222.2 115 ms [Estimated Role: Bud]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 2 192.168.140.2 213 ms [Estimated Role: Egress]
! 2 192.168.170.1 254 ms [Estimated Role: Egress]

! 3 192.168.222.2 108 ms [Estimated Role: Bud]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 3 192.168.170.1 164 ms [Estimated Role: Egress]
! 3 192.168.140.2 199 ms [Estimated Role: Egress]

! 4 192.168.170.1 198 ms [Estimated Role: Egress]
! 4 192.168.222.2 206 ms [Estimated Role: Bud]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500

This example shows an extract of the P2MP traceroute command with the responder-id option.



RP/0/RSP0/CPU0:router# traceroute mpls traffic-eng tunnel-mte 10 responder-id 10.3.0.1
Mon Apr 12 12:18:01.994 EST

Tracing MPLS MTE Label Switched Path on tunnel-mte10, timeout is 2.2 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

d 1 192.168.222.2 113 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]

d 2 192.168.222.2 118 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 2 192.168.170.1 244 ms [Estimated Role: Egress]

d 3 192.168.222.2 141 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 3 192.168.170.1 204 ms [Estimated Role: Egress]

d 4 192.168.222.2 110 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 4 192.168.170.1 174 ms [Estimated Role: Egress]

This example shows an extract of the P2MP traceroute command with the jitter option.


RP/0/RSP0/CPU0:router# traceroute mpls traffic-eng tunnel-mte 10 responder-id 10.3.0.1 ttl 4 jitter 500
Mon Apr 12 12:19:00.292 EST

Tracing MPLS MTE Label Switched Path on tunnel-mte10, timeout is 2.5 seconds

Codes: '!' - success, 'Q' - request not sent, '.' - timeout,
  'L' - labeled output interface, 'B' - unlabeled output interface, 
  'D' - DS Map mismatch, 'F' - no FEC mapping, 'f' - FEC mismatch,
  'M' - malformed request, 'm' - unsupported tlvs, 'N' - no rx label, 
  'P' - no rx intf label prot, 'p' - premature termination of LSP, 
  'R' - transit router, 'I' - unknown upstream index,
  'X' - unknown return code, 'x' - return code 0, 'd' - DDMAP

Type escape sequence to abort.

d 1 192.168.222.2 238 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]

d 2 192.168.222.2 188 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 2 192.168.170.1 290 ms [Estimated Role: Egress]

d 3 192.168.222.2 115 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 3 192.168.170.1 428 ms [Estimated Role: Egress]

d 4 192.168.222.2 127 ms [Estimated Role: Branch]
    [L] DDMAP 0: 192.168.140.2 192.168.140.2 MRU 1500 [Labels: 16001 Exp: 0]
    [L] DDMAP 1: 192.168.170.1 192.168.170.1 MRU 1500 [Labels: 16000 Exp: 0]
! 4 192.168.170.1 327 ms [Estimated Role: Egress]

Self-Ping Probe for Reoptimized LSP

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Self-Ping Probe for Reoptimized LSP

Release 7.5.3

You can now prevent traffic drops on a reoptimized label switch path (LSP) by timely confirmation that it's ready to handle the traffic. This confirmation is made possible by enabling the label edge router (LER) to send self-ping probes over the reoptimized LSP to the ingress LER. As soon the probe reaches the LER, there's confirmation that the RSVP programming is complete along the path. Post this confirmation, the LER switches traffic to the reoptimized LSP with no drop in traffic.

This feature introduces the self-ping keyword in the named-tunnels tunnel-te command.

During the reoptimization of LSP, the label edge router (LER) has to wait until the reoptimized path is established before switching the traffic onto the reoptimized LSP. If the LER does not wait long and the RSVP programming for establishing MPLS forwarding along the path is not complete at a given hop along the path, then traffic is dropped at that hop. An LER is a router that operates at the edge of an MPLS network and acts as the entry and exit points for the network.

Your edge router's hardware has an internal reopt-install timer that grants the reoptimized path enough time to set up and then switches traffic to the reoptimized path. If the LER waits too long before switching the traffic, then the traffic is still sent over the old path which can cause congestion. For now, operators use a conservative time to wait for switching the traffic to avoid traffic loss over the reoptimized LSP. Although this reopt-install timer is widely used in RSVP-TE, it still causes the old path to be used while the reoptimized path is fully ready, and could potentially cause traffic loss if some node along the path takes a longer time to program MPLS forwarding.

Self-Ping Probe Workflow

  • The LER does not start the reopt-install timer.

  • The LER sends the self-ping probe over the reoptimized LSP. By default, the frequency of the self-ping probe is one probe per second. The frequency at which the self-ping probes are sent is not configurable.

  • When the probe is received, the LER declares that the LSP is UP and then triggers the switchover of the tunnel traffic from the old LSP to the reoptimized LSP. The LER does not send any more probes over this LSP.

Key Concepts

Reoptimization occurs when a device with traffic engineering tunnels periodically examines tunnels with established LSPs to learn whether LSPs with better metrics are available and signal to that LSP. After the signaling is successful, the device replaces the older LSP with the reoptimized LSP.

In RSVP-TE networks, make-before-break or reoptimization is the mechanism of replacing an existing LSP without affecting the traffic that is carried on this LSP. The procedure in make-before-break is as follows:

  • Create and signal a reoptimized LSP.

  • Wait for this LSP to be ready to carry traffic or for the hardware programming to be complete at every hop in the path.

  • Switch the traffic from the existing LSP to the newly created LSP.

  • Wait for the hardware programming to be complete at the head, and then delete the existing or old LSP.

Configure Self-Ping Probe

Perform the following tasks to configure self-ping probe:

  • Configure self-ping probe

  • Configure maximum number of probes

Configuration Example


/* Configure Self-ping Probe */
Self-ping is supported for named-tunnels. The new keyword self-ping enables self-ping probe when tunnel-te ABC is being reoptimized.
Router# configure
Router(config)# mpls traffic-eng 
Router(config-mpls-te)# named-tunnels tunnel-te ABC  
Router(config-te-tun-name)# self-ping  
Router(config-te-tun-name)# commit  
 
/* Configure maximum number of probes */
You can configure the maximum number of probes before self-ping is considered unsuccessful.
Router# configure
Router(config)# mpls traffic-eng 
Router(config-mpls-te)# named-tunnels tunnel-te ABC  
Router(config-te-tun-name)# self-ping  
Router(config-te-tun-name)# max-count 10
Router(config-te-tun-name)# commit

Running Configuration

This section shows the running configuration of self-ping probe.


/* Self-ping probe configuration */
mpls traffic-eng
  named-tunnels
    tunnel-te ABC
      self-ping
     !

/* Configure maximum number of probes */
mpls traffic-eng
  named-tunnels
    tunnel-te ABC
      self-ping
         max-count 10
      !

Verification

Verify the self-ping probe configuration.


Router# show mpls traffic-eng tunnels name ABC detail
 
Name: ABC  Destination: 192.168.0.4  Ifhandle:0x2d0
  Tunnel-ID: 32783
  Status:
    Admin:    up Oper:   up   Path:  valid   Signalling: connected
 
    G-PID: 0x0800 (derived from egress interface properties)
    Bandwidth Requested: 0 kbps  CT0
    Creation Time: Thu Apr  7 14:54:30 2022 (00:00:01 ago)
  Config Parameters:
    Bandwidth:        0 kbps (CT0) Priority:  7  7 Affinity: 0x0/0xffff
    Metric Type: TE (global)
    Path Selection:
      Tiebreaker: Min-fill (default)
    Hop-limit: disabled
    Cost-limit: disabled
    Delay-limit: disabled
    Delay-measurement: disabled
    Path-invalidation timeout: 10000 msec (default), Action: Tear (default)
    AutoRoute: disabled  LockDown: disabled   Policy class: not set
    Forward class: 0 (not enabled)
    Forwarding-Adjacency: disabled
    Autoroute Destinations: 0
    Loadshare:          0 equal loadshares
    Load-interval: 300 seconds
    Auto-bw: disabled
    Auto-Capacity: Disabled:
    Self-ping: Enabled
      Maximum-probes: 10
      Probes-period: 1 second(s)
    Fast Reroute: Disabled, Protection Desired: None
    Path Protection: Not Enabled
    BFD Fast Detection: Disabled
    Reoptimization after affinity failure: Enabled
    Soft Preemption: Disabled
  Self-ping:
    Status: Not executed
  SNMP Index: 0
  Binding SID: 0
  History:
    Tunnel has been up for: 00:00:00 (since Thu Jan 01 01:00:00 BST 1970)
    Current LSP:
      Uptime: 00:00:00 (since Thu Jan 01 01:00:00 BST 1970)
  Current LSP Info:
    Instance: 2, Signaling Area: OSPF 100 area 0
    Uptime: 00:00:00 (since Thu Apr 07 14:54:31 BST 2022)
    Outgoing Interface: GigabitEthernet0/2/0/0, Outgoing Label: 24000
    Next Hop: 10.10.10.2      Neighbor Next Hop: 0.0.0.0
    Router-IDs: local      192.168.0.1
                downstream 192.168.0.2
    Soft Preemption: None
    SRLGs: not collected
    
      Record Route: Disabled
      Tspec: avg rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
      Session Attributes: Local Prot: Not Set, Node Prot: Not Set, BW Prot: Not Set
                          Soft Preemption Desired: Not Set
    Resv Info: None
      Record Route: Disabled
      Fspec: avg rate=0 kbits, burst=1000 bytes, peak rate=0 kbits
  Persistent Forwarding Statistics:
    Out Bytes: 0
    Out Packets: 0
 
Displayed 1 (of 1) heads, 0 (of 0) midpoints, 0 (of 0) tails
Displayed 1 up, 0 down, 0 recovering, 0 recovered heads

Verify the self-ping probe statistics.


Router# show mpls traffic-eng self-ping statistics
Wed Jun 15 14:24:29.316 BST
Self-Ping Statistics:
  Collected since: Tue Jun 14 09:35:52 2022 (1d04h ago)
  Operations:
    Started 2
    Running 0
    Successful 1
    Timed-out 1
    Terminated 0
  Probes sent 11
  Probes failed 0
  Received responses 1 (Average response time 00:00:00)
  Mismatched responses 0
 

During the self-ping procedure, the tunnel may go through various stages and the LER shows the status when you run the show mpls traffic-eng tunnels detail command.

  • Though you have configured the self-pring feature, there is no request for reoptimization and the status is shown as Not executed.

    
    Self-ping:
        Status: Not executed
    
  • The reoptimization is ongoing and the self-ping is actively sending probes and waiting to receive the response and status is shown as Underway.

    
    Self-ping:
        Status: Underway
        LSP-ID: 6
        Started: 00:00:00 (since Thu Apr 07 15:03:33 BST 2022)
    
  • When the self-ping receives the response and the traffic is switched to the reoptimized LSP. The status is shown as Succeeded.

    
    Self-ping:
        Status: Succeeded (in 0 seconds)
        LSP-ID: 4
        Probes sent: 1
        Started: 00:00:00 (since Thu Apr 07 15:02:23 BST 2022)
        Stopped: 00:00:00 (since Thu Apr 07 15:02:23 BST 2022)
        Response Received: 00:00:00 (since Thu Apr 07 15:02:23 BST 2022)
    
  • When the LER sends the self-ping probe and did not receive any response. The status is shown as Timed-out.

    The LER falls back to the reopt-install timer and LSP is considered active, and traffic is switched to the reoptimized LSP after the reopt-install timer expires.

    
      Self-ping:
        Status: Timed-out (in 9 seconds)
        LSP-ID: 6
        Probes sent: 10
        Started: 00:00:43 (since Thu Apr 07 15:03:33 BST 2022)
        Stopped: 00:00:34 (since Thu Apr 07 15:03:42 BST 2022)
    
  • The LER terminates self-ping execution when:

    • The reoptimized LSP has failed.

    • The reopt-install timer expires faster while the self-ping is still actively sending probes and receiving no response.

    The status is shown as Terminated.

    
    Self-ping:
        Status: Terminated (in 20 seconds)
        LSP-ID: 8
        Started: 00:00:21 (since Thu Apr 07 15:05:44 BST 2022)
        Stopped: 00:00:01 (since Thu Apr 07 15:06:04 BST 2022)