# PATH

PATH is a daemon that handles the installation and deletion of Segment Routing (SR) Policies.

## Starting PATH

Default configuration file for pathd is `pathd.conf`. The typical location of `pathd.conf` is /etc/frr/pathd.conf.

If the user is using integrated config, then `pathd.conf` need not be present and the `frr.conf` is read instead.

PATH supports all the common FRR daemon start options which are documented elsewhere.

## PCEP Support

A pceplib is included in the frr source tree and build by default.

To start pathd with pcep support the extra parameter -M pathd_pcep should be passed to the pathd daemon.

## Pathd Configuration

Example:

    debug pathd pcep basic
    segment-routing
     traffic-eng
      mpls-te on
      mpls-te import ospfv2
      segment-list SL1
       index 10 mpls label 16010
       index 20 mpls label 16030
      !
      segment-list SL2
       index 10 nai prefix 10.1.2.1/32 iface 1
       index 20 nai adjacency 10.1.20.1 10.1.20.2
       index 30 nai prefix 10.10.10.5/32 algorithm 0
       index 40 mpls label 18001
      !
      policy color 1 endpoint 1.1.1.1
       name default
       binding-sid 4000
       candidate-path preference 100 name CP1 explicit segment-list SL1
       candidate-path preference 200 name CP2 dynamic
        affinity include-any 0x000000FF
        bandwidth 100000
        metric bound msd 16 required
        metric te 10
        objective-function mcp required
      !
      pcep
       pce-config GROUP1
        source-address ip 1.1.1.1
        tcp-md5-auth secret
        timer keep-alive 30
       !
       pce PCE1
        config GROUP1
        address ip 10.10.10.10
       !
       pce PCE2
        config GROUP1
        address ip 9.9.9.9
       !
       pcc
        peer PCE1 precedence 10
        peer PCE2 precedence 20
       !
      !
     !
    !

### Configuration Commands

segment-routing

  Configure segment routing.

traffic-eng

  Configure segment routing traffic engineering.

mpls-te <on|off>

  Activate/Deactivate use of internal Traffic Engineering Database

mpls-te import <ospfv2|ospfv3|isis>

  Load data from the selected igp

segment-list NAME

  Delete or start a segment list definition.

index INDEX mpls label LABEL

index INDEX nai adjacency A.B.C.D A.B.C.D

index INDEX nai prefix A.B.C.D/M algorithm <0|1>

index INDEX nai prefix A.B.C.D/M iface (0-65535)

  Delete or specify a segment in a segment list definition.

policy color COLOR endpoint ENDPOINT

  Delete or start a policy definition.

name NAME

  Specify the policy name.

binding-sid LABEL

  Specify the policy SID.

candidate-path preference PREFERENCE name NAME explicit segment-list SEGMENT-LIST-NAME

  Delete or define an explicit candidate path.

candidate-path preference PREFERENCE name NAME dynamic

  Delete or start a dynamic candidate path definition.

affinity <exclude-any|include-any|include-all> BITPATTERN

  Delete or specify an affinity constraint for a dynamic candidate path.

bandwidth BANDWIDTH [required]

  Delete or specify a bandwidth constraint for a dynamic candidate path.

metric [bound] METRIC VALUE [required]

  Delete or specify a metric constraint for a dynamic candidate path.

  The possible metrics are:

    - igp: IGP metric

    - te: TE metric

    - hc: Hop Counts

    - abc: Aggregate bandwidth consumption

    - mll: Load of the most loaded link

    - igp: Cumulative IGP cost

    - cte: Cumulative TE cost

    - igp: P2MP IGP metric

    - pte: P2MP TE metric

    - phc: P2MP hop count metric

    - msd: Segment-ID (SID) Depth

    - pd: Path Delay metric

    - pdv: Path Delay Variation metric

    - pl: Path Loss metric

    - ppd: P2MP Path Delay metric

    - pdv: P2MP Path Delay variation metric

    - ppl: P2MP Path Loss metric

    - nap: Number of adaptations on a path

    - nlp: Number of layers on a path

    - dc: Domain Count metric

    - bnc: Border Node Count metric

objective-function OBJFUN1 [required]

  Delete or specify a PCEP objective function constraint for a dynamic candidate path.

  The possible functions are:

    - mcp: Minimum Cost Path [RFC5541]

    - mlp: Minimum Load Path [RFC5541]

    - mbp: Maximum residual Bandwidth Path [RFC5541]

    - mbc: Minimize aggregate Bandwidth Consumption [RFC5541]

    - mll: Minimize the Load of the most loaded Link [RFC5541]

    - mcc: Minimize the Cumulative Cost of a set of paths [RFC5541]

    - spt: Shortest Path Tree [RFC8306]

    - mct: Minimum Cost Tree [RFC8306]

    - mplp: Minimum Packet Loss Path [RFC8233]

    - mup: Maximum Under-Utilized Path [RFC8233]

    - mrup: Maximum Reserved Under-Utilized Path [RFC8233]

    - mtd: Minimize the number of Transit Domains [RFC8685]

    - mbn: Minimize the number of Border Nodes [RFC8685]

    - mctd: Minimize the number of Common Transit Domains [RFC8685]

    - msl: Minimize the number of Shared Links [RFC8800]

    - mss: Minimize the number of Shared SRLGs [RFC8800]

    - msn: Minimize the number of Shared Nodes [RFC8800]

debug pathd pcep [basic|path|message|pceplib]

  Enable or disable debugging for the pcep module:

  > - basic: Enable basic PCEP logging

  > - path: Log the path structures

  > - message: Log the PCEP messages

  > - pceplib: Enable pceplib logging

pcep

  Configure PCEP support.

pce-config NAME

  Define a shared PCE configuration that can be used in multiple PCE declarations.

pce NAME

  Define or delete a PCE definition.

config WORD

  Select a shared configuration. If not defined, the default configuration will be used.

address <ip A.B.C.D | ipv6 X:X::X:X> [port (1024-65535)]

  Define the address and port of the PCE.

  If not specified, the port is the standard PCEP port 4189.

  This should be specified in the PCC peer definition.

source-address [ip A.B.C.D | ipv6 X:X::X:X] [port PORT]

  Define the address and/or port of the PCC as seen by the PCE. This can be used in a configuration group or a PCC peer declaration.

  If not specified, the source address will be the router identifier selected by zebra, and the port will be the standard PCEP port 4189.

  This can be specified in either the PCC peer definition or in a configuration group.

tcp-md5-auth WORD

  Enable TCP MD5 security with the given secret.

  This can be specified in either the PCC peer definition or in a configuration group.

sr-draft07

  Specify if a PCE only support segment routing draft 7, this flag will limit the PCC behavior to this draft.

  This can be specified in either the PCC peer definition or in a configuration group.

pce-initiated

  Specify if PCE-initiated LSP should be allowed for this PCE.

  This can be specified in either the PCC peer definition or in a configuration group.

timer [keep-alive (1-63)] [min-peer-keep-alive (1-255)] [max-peer-keep-alive (1-255)] [dead-timer (4-255)] [min-peer-dead-timer (4-255)] [max-peer-dead-timer (4-255)] [pcep-request (1-120)] [session-timeout-interval (1-120)] [delegation-timeout (1-60)]

  Specify the PCEP timers.

  This can be specified in either the PCC peer definition or in a configuration group.

pcc

  Disable or start the definition of a PCC.

msd (1-32)

  Specify the maximum SID depth in a PCC definition.

peer WORD [precedence (1-255)]

  Specify a peer and its precedence in a PCC definition.

### Introspection Commands

show sr-te policy [detail]

  Display the segment routing policies.

    router# show sr-te policy

     Endpoint  Color  Name     BSID  Status
     ------------------------------------------
     1.1.1.1   1      default  4000  Active

    router# show sr-te policy detail

    Endpoint: 1.1.1.1  Color: 1  Name: LOW_DELAY  BSID: 4000  Status: Active
        Preference: 100  Name: cand1  Type: explicit  Segment-List: sl1  Protocol-Origin: Local
      * Preference: 200  Name: cand1  Type: dynamic  Segment-List: 32453452  Protocol-Origin: PCEP

The asterisk (*) marks the best, e.g. active, candidate path. Note that for segment-lists which are retrieved via PCEP a random number based name is generated.

show sr-te pcep counters

  Display the counters from pceplib.

show sr-te pcep pce-config [NAME]

  Display a shared configuration. if no name is specified, the default configuration will be displayed.

show sr-te pcep pcc

  Display PCC information.

show sr-te pcep session [NAME]

  Display the information of a PCEP session, if not name is specified all the sessions will be displayed.

### Utility Commands

clear sr-te pcep session [NAME]

  Reset the pcep session by disconnecting from the PCE and performing the normal reconnection process. No configuration is changed.

## Usage with BGP route-maps

It is possible to steer traffic 'into' a segment routing policy for routes learned through BGP using route-maps:

    route-map SET_SR_POLICY permit 10
     set sr-te color 1
    !
    router bgp 1
     bgp router-id 2.2.2.2
     neighbor 1.1.1.1 remote-as 1
     neighbor 1.1.1.1 update-source lo
     !
     address-family ipv4 unicast
      neighbor 1.1.1.1 next-hop-self
      neighbor 1.1.1.1 route-map SET_SR_POLICY in
      redistribute static
     exit-address-family
     !
    !

In this case, the SR Policy with color 1 and endpoint 1.1.1.1 is selected.

## Sample configuration

    ! Default pathd configuration sample
    !
    password frr
    log stdout

    segment-routing
     traffic-eng
      segment-list test1
       index 10 mpls label 123
       index 20 mpls label 456
      !
      segment-list test2
       index 10 mpls label 321
       index 20 mpls label 654
      !
      policy color 1 endpoint 1.1.1.1
       name one
       binding-sid 100
       candidate-path preference 100 name test1 explicit segment-list test1
       candidate-path preference 200 name test2 explicit segment-list test2
      !
      policy color 2 endpoint 2.2.2.2
       name two
       binding-sid 101
       candidate-path preference 100 name def explicit segment-list test2
       candidate-path preference 200 name dyn dynamic
        bandwidth 12345
        metric bound abc 16 required
        metric te 10
       !
      !
      pcep
       pcc-peer PCE1
        address ip 127.0.0.1
        sr-draft07
       !
       pcc
        peer PCE1
       !
     !
    !