Merge pull request #977 from fett0/sr-mpls-correction

Segment-rounting : Add documentation about segment-routing mpls on VyOS

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+.. _segment-routing:
+
+###############
+Segment Routing
+###############
+
+Segment Routing (SR) is a network architecture that is similar to source-routing
+. In this architecture, the ingress router adds a list of segments, known as 
+SIDs, to the packet as it enters the network. These segments represent different 
+portions of the network path that the packet will take.
+
+The SR segments are portions of the network path taken by the packet, and are 
+called SIDs. At each node, the first SID of the list is read, executed as a 
+forwarding function, and may be popped to let the next node read the next SID of 
+the list. The SID list completely determines the path where the packet is 
+forwarded.
+
+Segment Routing can be applied to an existing MPLS-based data plane and defines
+a control plane network architecture. In MPLS networks, segments are encoded as
+MPLS labels and are added at the ingress router. These MPLS labels are then 
+exchanged and populated by Interior Gateway Protocols (IGPs) like IS-IS or OSPF 
+which are running on most ISPs.
+
+
+.. note:: Segment routing defines a control plane network architecture and
+  can be applied to an existing MPLS based dataplane. In the MPLS networks,
+  segments are encoded as MPLS labels and are imposed at the ingress router.
+  MPLS labels are exchanged and populated by IGPs like IS-IS.Segment Routing
+  as per RFC8667 for MPLS dataplane. It supports IPv4, IPv6 and ECMP and has
+  been tested against Cisco & Juniper routers.however,this deployment is still
+  EXPERIMENTAL for FRR.
+ 
+
+IS-IS SR Configuration
+----------------------
+
+Segment routing (SR) is used by the IGP protocols to interconnect network
+devices, below configuration shows how to enable SR on IS-IS:
+
+
+.. note:: ``Known limitations:`` 
+
+  No support for level redistribution (L1 to L2 or L2 to L1)
+
+  No support for binding SID
+
+  No support for SRLB
+
+  Only one SRGB and default SPF Algorithm is supported
+
+
+
+.. cfgcmd::  set protocols isis segment-routing global-block high-label-value 
+  <label-value>
+
+  Set the Segment Routing Global Block i.e. the label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.
+
+.. cfgcmd:: set protocols isis segment-routing global-block low-label-value 
+  <label-value>
+
+  Set the Segment Routing Global Block i.e. the low label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.
+ 
+.. cfgcmd:: set protocols isis segment-routing local-block high-label-value 
+  <label-value>
+
+  Set the Segment Routing Local Block i.e. the label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.Segment Routing Local Block, The negative command always 
+  unsets both.
+
+.. cfgcmd:: set protocols isis segment-routing local-block <low-label-value 
+  <label-value>
+
+  Set the Segment Routing Local Block i.e. the low label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.Segment Routing Local Block, The negative command always 
+  unsets both.
+
+.. cfgcmd:: set protocols isis segment-routing maximum-label-depth <1-16>
+
+  Set the Maximum Stack Depth supported by the router. The value depend of
+  the MPLS dataplane.
+
+.. cfgcmd:: set protocols isis segment-routing prefix <address> index value 
+  <0-65535>
+   
+  A segment ID that contains an IP address prefix calculated by an IGP in the
+  service provider core network. Prefix SIDs are globally unique, this value
+  indentify it 
+
+.. cfgcmd:: set protocols isis segment-routing prefix <address> index
+   <no-php-flag | explicit-null| n-flag-clear>
+
+   this option allows to configure prefix-sid on SR. The ‘no-php-flag’ means NO 
+   Penultimate Hop Popping that allows SR node to request to its neighbor to 
+   not pop the label. The ‘explicit-null’ flag allows SR node to request to its 
+   neighbor to send IP packet with the EXPLICIT-NULL label. The ‘n-flag-clear’ 
+   option can be used to explicitly clear the Node flag that is set by default 
+   for Prefix-SIDs associated to loopback addresses. This option is necessary 
+   to configure Anycast-SIDs.
+
+
+.. opcmd:: show isis segment-routing node
+ 
+   Show detailed information about all learned Segment Routing Nodes
+
+.. opcmd:: show isis route prefix-sid
+
+   Show detailed information about prefix-sid and label learned
+
+.. note:: more information related IGP  - :ref:`routing-isis`
+
+   
+
+OSPF SR  Configuration
+----------------------
+
+Segment routing (SR) is used by the IGP protocols to interconnect network
+devices, below configuration shows how to enable SR on OSPF:
+
+.. cfgcmd:: set protocols ospf parameters opaque-lsa
+
+  Enable the Opaque-LSA capability (rfc2370), necessary to transport label 
+  on IGP
+
+
+.. cfgcmd:: set protocols ospf segment-routing global-block high-label-value 
+  <label-value>
+
+  Set the Segment Routing Global Block i.e. the label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.
+
+.. cfgcmd:: set protocols ospf segment-routing global-block low-label-value 
+  <label-value>
+
+  Set the Segment Routing Global Block i.e. the low label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.
+
+.. cfgcmd:: set protocols ospf segment-routing local-block high-label-value 
+  <label-value>
+
+  Set the Segment Routing Local Block i.e. the label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.Segment Routing Local Block, The negative command always 
+  unsets both.
+
+.. cfgcmd:: set protocols ospf segment-routing local-block <low-label-value 
+  <label-value>
+
+  Set the Segment Routing Local Block i.e. the low label range used by MPLS to 
+  store label in the MPLS FIB for Prefix SID. Note that the block size may 
+  not exceed 65535.Segment Routing Local Block, The negative command always 
+  unsets both.
+
+.. cfgcmd:: set protocols ospf segment-routing maximum-label-depth <1-16>
+
+  Set the Maximum Stack Depth supported by the router. The value depend of
+  the MPLS dataplane.
+
+.. cfgcmd:: set protocols ospf segment-routing prefix <address> index value 
+  <0-65535>
+   
+  A segment ID that contains an IP address prefix calculated by an IGP in the
+  service provider core network. Prefix SIDs are globally unique, this value
+  indentify it 
+
+.. cfgcmd:: set protocols ospf segment-routing prefix <address> index
+   <no-php-flag | explicit-null| n-flag-clear>
+
+   this option allows to configure prefix-sid on SR. The ‘no-php-flag’ means NO 
+   Penultimate Hop Popping that allows SR node to request to its neighbor to 
+   not pop the label. The ‘explicit-null’ flag allows SR node to request to its 
+   neighbor to send IP packet with the EXPLICIT-NULL label. The ‘n-flag-clear’ 
+   option can be used to explicitly clear the Node flag that is set by default 
+   for Prefix-SIDs associated to loopback addresses. This option is necessary 
+   to configure Anycast-SIDs.
+
+.. note:: more information related IGP  - :ref:`routing-ospf`
+
+Configuration Example
+---------------------
+
+we described the configuration SR ISIS / SR OSPF using 2 connected with them to
+share label information.
+
+Enable IS-IS with Segment Routing (Experimental)
+================================================
+
+**Node 1:**
+
+.. code-block:: none
+
+  set interfaces loopback lo address '192.168.255.255/32'
+  set interfaces ethernet eth1 address '192.0.2.1/24'
+
+  set protocols isis interface eth1
+  set protocols isis interface lo
+  set protocols isis net '49.0001.1921.6825.5255.00'
+  set protocols isis segment-routing global-block high-label-value '599'
+  set protocols isis segment-routing global-block low-label-value '550'
+  set protocols isis segment-routing prefix 192.168.255.255/32 index value '1'
+  set protocols isis segment-routing prefix 192.168.255.255/32 index explicit-null
+  set protocols mpls interface 'eth1'
+  
+**Node 2:**
+
+.. code-block:: none
+
+  set interfaces loopback lo address '192.168.255.254/32'
+  set interfaces ethernet eth1 address '192.0.2.2/24'
+
+  set protocols isis interface eth1
+  set protocols isis interface lo
+  set protocols isis net '49.0001.1921.6825.5254.00'
+  set protocols isis segment-routing global-block high-label-value '599'
+  set protocols isis segment-routing global-block low-label-value '550'
+  set protocols isis segment-routing prefix 192.168.255.254/32 index value '2'
+  set protocols isis segment-routing prefix 192.168.255.254/32 index explicit-null
+  set protocols mpls interface 'eth1'
+  
+  
+  
+This gives us MPLS segment routing enabled and labels for far end loopbacks:
+
+.. code-block:: none
+
+  Node-1@vyos:~$ show mpls table
+   Inbound Label  Type        Nexthop                Outbound Label
+   ----------------------------------------------------------------------
+   552            SR (IS-IS)  192.0.2.2              IPv4 Explicit Null <-- Node-2 loopback learned on Node-1
+   15000          SR (IS-IS)  192.0.2.2              implicit-null
+   15001          SR (IS-IS)  fe80::e87:6cff:fe09:1  implicit-null
+   15002          SR (IS-IS)  192.0.2.2              implicit-null
+   15003          SR (IS-IS)  fe80::e87:6cff:fe09:1  implicit-null
+
+  Node-2@vyos:~$ show mpls table
+   Inbound Label  Type        Nexthop               Outbound Label
+   ---------------------------------------------------------------------
+   551            SR (IS-IS)  192.0.2.1             IPv4 Explicit Null <-- Node-1 loopback learned on Node-2
+   15000          SR (IS-IS)  192.0.2.1             implicit-null
+   15001          SR (IS-IS)  fe80::e33:2ff:fe80:1  implicit-null
+   15002          SR (IS-IS)  192.0.2.1             implicit-null
+   15003          SR (IS-IS)  fe80::e33:2ff:fe80:1  implicit-null
+
+Here is the routing tables showing the MPLS segment routing label operations:
+
+.. code-block:: none
+
+  Node-1@vyos:~$ show ip route isis
+  Codes: K - kernel route, C - connected, S - static, R - RIP,
+         O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
+         T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
+         f - OpenFabric,
+         > - selected route, * - FIB route, q - queued, r - rejected, b - backup
+         t - trapped, o - offload failure
+
+  I   192.0.2.0/24 [115/20] via 192.0.2.2, eth1 inactive, weight 1, 00:07:48
+  I>* 192.168.255.254/32 [115/20] via 192.0.2.2, eth1, label IPv4 Explicit Null, weight 1, 00:03:39
+
+  Node-2@vyos:~$ show ip route isis
+  Codes: K - kernel route, C - connected, S - static, R - RIP,
+         O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
+         T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
+         f - OpenFabric,
+         > - selected route, * - FIB route, q - queued, r - rejected, b - backup
+         t - trapped, o - offload failure
+
+  I   192.0.2.0/24 [115/20] via 192.0.2.1, eth1 inactive, weight 1, 00:07:46
+  I>* 192.168.255.255/32 [115/20] via 192.0.2.1, eth1, label IPv4 Explicit Null, weight 1, 00:03:43
+
+
+Enable OSPF with Segment Routing (Experimental):
+================================================
+
+**Node 1**
+
+.. code-block:: none
+
+  set interfaces loopback lo address 10.1.1.1/32
+  set interfaces ethernet eth0 address 192.168.0.1/24
+  set protocols ospf area 0 network '192.168.0.0/24'
+  set protocols ospf area 0 network '10.1.1.1/32'
+  set protocols ospf parameters opaque-lsa
+  set protocols ospf parameters router-id '10.1.1.1'
+  set protocols ospf segment-routing global-block high-label-value '1100'
+  set protocols ospf segment-routing global-block low-label-value '1000'
+  set protocols ospf segment-routing prefix 10.1.1.1/32 index explicit-null
+  set protocols ospf segment-routing prefix 10.1.1.1/32 index value '1'
+
+**Node 2**
+
+.. code-block:: none
+
+  set interfaces loopback lo address 10.1.1.2/32
+  set interfaces ethernet eth0 address 192.168.0.2/24
+  set protocols ospf area 0 network '192.168.0.0/24'
+  set protocols ospf area 0 network '10.1.1.2/32'
+  set protocols ospf parameters opaque-lsa
+  set protocols ospf parameters router-id '10.1.1.2'
+  set protocols ospf segment-routing global-block high-label-value '1100'
+  set protocols ospf segment-routing global-block low-label-value '1000'
+  set protocols ospf segment-routing prefix 10.1.1.2/32 index explicit-null
+  set protocols ospf segment-routing prefix 10.1.1.2/32 index value '2'
+
+
+This gives us MPLS segment routing enabled and labels for far end loopbacks:
+
+.. code-block:: none
+
+  Node-1@vyos:~$ show mpls table
+   Inbound Label  Type       Nexthop      Outbound Label
+   -----------------------------------------------------------
+   1002           SR (OSPF)  192.168.0.2  IPv4 Explicit Null  <-- Node-2 loopback learned on Node-1
+   15000          SR (OSPF)  192.168.0.2  implicit-null
+   15001          SR (OSPF)  192.168.0.2  implicit-null
+
+  Node-2@vyos:~$ show mpls table
+   Inbound Label  Type       Nexthop      Outbound Label
+   -----------------------------------------------------------
+   1001           SR (OSPF)  192.168.0.1  IPv4 Explicit Null  <-- Node-1 loopback learned on Node-2
+   15000          SR (OSPF)  192.168.0.1  implicit-null
+   15001          SR (OSPF)  192.168.0.1  implicit-null
+
+Here is the routing tables showing the MPLS segment routing label operations:
+
+.. code-block:: none
+
+  Node-1@vyos:~$ show ip route ospf
+  Codes: K - kernel route, C - connected, S - static, R - RIP,
+         O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
+         T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
+         f - OpenFabric,
+         > - selected route, * - FIB route, q - queued, r - rejected, b - backup
+         t - trapped, o - offload failure
+
+  O   10.1.1.1/32 [110/0] is directly connected, lo, weight 1, 00:03:43
+  O>* 10.1.1.2/32 [110/1] via 192.168.0.2, eth0, label IPv4 Explicit Null, weight 1, 00:03:32
+  O   192.168.0.0/24 [110/1] is directly connected, eth0, weight 1, 00:03:43
+
+  Node-2@vyos:~$ show ip route ospf
+  Codes: K - kernel route, C - connected, S - static, R - RIP,
+         O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
+         T - Table, v - VNC, V - VNC-Direct, A - Babel, F - PBR,
+         f - OpenFabric,
+         > - selected route, * - FIB route, q - queued, r - rejected, b - backup
+         t - trapped, o - offload failure
+
+  O>* 10.1.1.1/32 [110/1] via 192.168.0.1, eth0, label IPv4 Explicit Null, weight 1, 00:03:36
+  O   10.1.1.2/32 [110/0] is directly connected, lo, weight 1, 00:03:51
+  O   192.168.0.0/24 [110/1] is directly connected, eth0, weight 1, 00:03:51
+