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frr/doc/user/pathd.rst
Sebastien Merle 4d7b695d3a pathd: New SR-TE policy management daemon 
This new daemon manages Segment-Routing Traffic-Engineering
(SR-TE) Policies and installs them into zebra. It provides
the usual yang support and vtysh commands to define or change
SR-TE Policies.

In a nutshell SR-TE Policies provide the possibility to steer
traffic through a (possibly dynamic) list of Segment Routing
segments to the endpoint of the policy. This list of segments
is part of a Candidate Path which again belongs to the SR-TE
Policy. SR-TE Policies are uniquely identified by their color
and endpoint. The color can be used to e.g. match BGP
communities on incoming traffic.

There can be multiple Candidate Paths for a single
policy, the active Candidate Path is chosen according to
certain conditions of which the most important is its
preference. Candidate Paths can be explicit (fixed list of
segments) or dynamic (list of segment comes from e.g. PCEP, see
below).

Configuration example:

segment-routing
 traffic-eng
  segment-list SL
   index 10 mpls label 1111
   index 20 mpls label 2222
  !
  policy color 4 endpoint 10.10.10.4
   name POL4
   binding-sid 104
   candidate-path preference 100 name exp explicit segment-list SL
   candidate-path preference 200 name dyn dynamic
  !
 !
!

There is an important connection between dynamic Candidate
Paths and the overall topic of Path Computation. Later on for
pathd a dynamic module will be introduced that is capable
of communicating via the PCEP protocol with a PCE (Path
Computation Element) which again is capable of calculating
paths according to its local TED (Traffic Engineering Database).
This dynamic module will be able to inject the mentioned
dynamic Candidate Paths into pathd based on calculated paths
from a PCE.

https://tools.ietf.org/html/draft-ietf-spring-segment-routing-policy-06

Co-authored-by: Sebastien Merle <sebastien@netdef.org>
Co-authored-by: Renato Westphal <renato@opensourcerouting.org>
Co-authored-by: GalaxyGorilla <sascha@netdef.org>
Co-authored-by: Emanuele Di Pascale <emanuele@voltanet.io>
Signed-off-by: Sebastien Merle <sebastien@netdef.org>
2020-12-18 16:34:02 +01:00

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.. _path:
****
PATH
****
:abbr:`PATH` is a daemon that handles the installation and deletion
of Segment Routing (SR) Policies.
.. _starting-path:
Starting PATH
=============
Default configuration file for *pathd* is :file:`pathd.conf`. The typical
location of :file:`pathd.conf` is |INSTALL_PREFIX_ETC|/pathd.conf.
If the user is using integrated config, then :file:`pathd.conf` need not be
present and the :file:`frr.conf` is read instead.
.. program:: pathd
:abbr:`PATH` supports all the common FRR daemon start options which are
documented elsewhere.
Pathd Configuration
===================
Example:
.. code-block:: frr
segment-routing
traffic-eng
segment-list SL1
index 10 mpls label 16010
index 20 mpls label 16030
!
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
!
!
!
.. _path-commands:
Configuration Commands
----------------------
.. index:: segment-routing
.. clicmd:: segment-routing
Configure segment routing.
.. index:: traffic-eng
.. clicmd:: traffic-eng
Configure segment routing traffic engineering.
.. index:: [no] segment-list NAME
.. clicmd:: [no] segment-list NAME
Delete or start a segment list definition.
.. index:: [no] index INDEX mpls label LABEL [nai node ADDRESS]
.. clicmd:: [no] index INDEX mpls label LABEL [nai node ADDRESS]
Delete or specify a segment in a segment list definition.
.. index:: [no] policy color COLOR endpoint ENDPOINT
.. clicmd:: [no] policy color COLOR endpoint ENDPOINT
Delete or start a policy definition.
.. index:: name NAME
.. clicmd:: name NAME
Specify the policy name.
.. index:: binding-sid LABEL
.. clicmd:: binding-sid LABEL
Specify the policy SID.
.. index:: [no] candidate-path preference PREFERENCE name NAME explicit segment-list SEGMENT-LIST-NAME
.. clicmd:: [no] candidate-path preference PREFERENCE name NAME explicit segment-list SEGMENT-LIST-NAME
Delete or define an explicit candidate path.
.. index:: [no] candidate-path preference PREFERENCE name NAME dynamic
.. clicmd:: [no] candidate-path preference PREFERENCE name NAME dynamic
Delete or start a dynamic candidate path definition.
.. index:: [no] affinity {exclude-any|include-any|include-all} BITPATTERN
.. clicmd:: [no] affinity {exclude-any|include-any|include-all} BITPATTERN
Delete or specify an affinity constraint for a dynamic candidate path.
.. index:: [no] bandwidth BANDWIDTH [required]
.. clicmd:: [no] bandwidth BANDWIDTH [required]
Delete or specify a bandwidth constraint for a dynamic candidate path.
.. index:: [no] metric [bound] METRIC VALUE [required]
.. clicmd:: [no] 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
.. index:: [no] objective-function OBJFUN1 [required]
.. clicmd:: [no] 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]
Introspection Commands
----------------------
.. index:: show sr-te policy [detail]
.. clicmd:: show sr-te policy [detail]
Display the segment routing policies.
.. code-block:: frr
router# show sr-te policy
Endpoint Color Name BSID Status
------------------------------------------
1.1.1.1 1 default 4000 Active
.. code-block:: frr
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.
Usage with BGP route-maps
=========================
It is possible to steer traffic 'into' a segment routing policy for routes
learned through BGP using route-maps:
.. code-block:: frr
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.
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