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diff --git a/docs/gettingstarted/developers/fib20/mplsfib.rst b/docs/gettingstarted/developers/fib20/mplsfib.rst deleted file mode 100644 index f66724ea81b..00000000000 --- a/docs/gettingstarted/developers/fib20/mplsfib.rst +++ /dev/null @@ -1,220 +0,0 @@ -.. _mplsfib: - -MPLS FIB --------- - -Implementation -^^^^^^^^^^^^^^^ - -The MPLS FIB is implemented using exactly the same data structures as -the IP FIB. The only difference is the implementation of the -table. Whereas for IPv4 this is an mtrie and for IPv6 a hash table, -for MPLS it is a flat array indexed by a 21 bit key (label & EOS -bit). This implementation is chosen to favour packet forwarding speed. - -It can be the case in MPLS forwarding that packets received with the -EOS bit set in the MPLS label need to be forwarded differently from -those without. The most common example of this is if the path set -contains a path that does not have an output label. In this case the -non-EOS packets cannot take this path, because to do so would expose -the neighbouring router to a label that it did not allocate. - -The desgin choice to make with an MPLS FIB table is therefore: -- 20 bit key: label only. When the EOS and non-EOS actions differ the result is a 'EOS-choice' object. -- 21 bit key: label and EOS-bit. The result is then the specific action based on EOS-bit. - -20 bit key - - Advantages:lower memory overhead, since there are few DB entries. - - Disadvantages: slower DP performance in the case the path-lists - differ, as more objects are encounterd in the switch path - -21 bit key - - Advantages: faster DP performance - Disadvantages: increased memory footprint. - -Switching between schemes based on observed/measured action similarity -is not considered on the grounds of complexity and flip-flopping. - -VPP mantra - favour performance over memory. We choose a 21 bit key. - -Basics -^^^^^^ - -MPLS is not enabled by default. There are two steps to get -started. First, create the default MPLS FIB: - -.. code-block:: console - - $ mpls table add 0 - -With '0' being the magic number for the 'default' table (just like it -is for IPv[46]). One can create other MPLS tables, but, unlike IP -tables, one cannot 'bind' non-default MPLS tables to interfaces, in -other words all MPLS packets received on an interface will always -result in a lookup in the default table. One has to be more inventive -to use the non-default tables... - -Secondly, for *each* interface on which you wish to *receive* MPLS -packets, that interface must be MPLS 'enabled' - -.. code-block:: console - - $ set interface mpls GigEthernet0/0/0 enable - -there is no equivalent enable for transmit, all that is required is to -use an interface as an egress path. - -Entries in the MPLS FIB can be displayed with: - -.. code-block:: console - - $ sh mpls fib [table X] [label] - -There is a tight coupling between IP and MPLS forwarding. MPLS -forwarding equivalence classes (FECs) are often an IP prefix – that is -to say that traffic matching a given IP prefix is routed into a MPLS -label switch path (LSP). It is thus necessary to be able to associate -a given prefix/route with an [out-going] MPLS label that will be -imposed when the packet is forwarded. This is configured as: - -.. code-block:: console - - $ ip route add 1.1.1.1/32 via 10.10.10.10 GigEthernet0/0/0 out-labels 33 - -packets matching 1.1.1.1/32 will be forwarded out GigEthernet0/0/0 and have -MPLS label 33 imposed. More than one out-going label can be -specified. Out-going MPLS labels can be applied to recursive and -non-recursive routes, e.g; - -.. code-block:: console - - $ ip route add 2.2.2.0/24 via 1.1.1.1 out-labels 34 - -packets matching 2.2.2.0/24 will thus have two MPLS labels imposed; 34 -and 33. This is the realisation of, e,g, an MPLS BGP VPNv4. - -To associate/allocate a local-label for a prefix, and thus have -packets to that local-label forwarded equivalently to the prefix do; - -.. code-block:: console - - $ mpls local-label 99 2.2.2.0/24 - -In the API this action is called a ‘bind’. -The router receiving the MPLS encapsulated packets needs to be -programmed with actions associated which each label value – this is -the role of the MPLS FIB. The MPLS FIB is a table, whose key is the -MPLS label value and end-of-stack (EOS) bit, which stores the action -to perform on packets with matching encapsulation. Currently supported -actions are: - -#. Pop the label and perform an IPv[46] lookup in a specified table -#. Pop the label and forward via a specified next-hop (this is penultimate-hop-pop, PHP) -#. Swap the label and forward via a specified next-hop. - -These can be programmed respectively by: - -.. code-block:: console - - $ mpls local-label 33 eos ip4-lookup-in-table X - $ mpls local-label 33 [eos] via 10.10.10.10 GigEthernet0/0/0 - $ mpls local-label 33 [eos] via 10.10.10.10 GigEthernet0/0/0 out-labels 66 - -the latter is an example of an MPLS cross connect. Any description of -a next-hop, recursive, non-recursive, labelled, non-labelled, etc, -that is valid for an IP prefix, is also valid for an MPLS -local-label. Note the use of the 'eos' keyword which indicates the -programming is for the case when the label is end-of-stack. The last -two operations can apply to both eos and non-eos packets, but the pop -and IP lookup only to an eos packet. - - -MPLS VPN -^^^^^^^^ - -To configure an MPLS VPN for a PE the following example can be used. - -Step 1; Configure routes to the iBGP peers - note these route MUST -have out-going labels; - -.. code-block:: console - - $ ip route add 10.0.0.1/32 via 192.168.1.2 Eth0 out-labels 33 - $ ip route add 10.0.0.2/32 via 192.168.2.2 Eth0 out-labels 34 - -Step 2; Configure the customer 'VRF' - -.. code-block:: console - - $ ip table add 2 - -Step 3; add a route via the iBGP peer[s] with the MPLS label -advertised by that peer - -.. code-block:: console - - $ ip route add table 2 10.10.10.0/24 via 10.0.0.2 next-hop-table 0 out-label 122 - $ ip route add table 2 10.10.10.0/24 via 10.0.0.1 next-hop-table 0 out-label 121 - -Step 4; add a route via the eBGP peer - -.. code-block:: console - - $ ip route add table 2 10.10.20.0/24 via 172.16.0.1 next-hop-table 2 - -Step 5; depending on the label allocation scheme used, add routes to -the MPLS FIB to accept incoming labelled packets: - -#. per-prefix label scheme - this command 'binds' the label to the same - forwarding as the IP route - - .. code-block:: console - - $ mpls local-label 99 10.10.20.0/24 - -#. per-CE label scheme - this pops the incoming label and forwards via - the next-hop provided. Append config for 'out-labels' if so desired. - - .. code-block:: console - - $ mpls local-label 99 via 172.16.0.1 next-hop-table 2 - -#. per-VRF label scheme - - .. code-block:: console - - $ mpls local-label 99 via ip4-lookup-in-table 2 - -MPLS Tunnels -^^^^^^^^^^^^ - -MPLS tunnels are unidirectional and can impose a stack of labels. They -are 'normal' interfaces and thus can be used, for example, as the -target for IP routes and L2 cross-connects. To construct a tunnel: - -.. code-block:: console - - $ mpls tunnel add via 10.10.10.10 GigEthernet0/0/0 out-labels 33 44 55 - -and to then have that created tunnel to perform ECMP: - -.. code-block:: console - - $ mpls tunnel add mpls-tunnel0 via 10.10.10.11 GigEthernet0/0/0 out-labels 66 77 88 - -use - -.. code-block:: console - - $ sh mpls tunnel [X] - -to see the monster you have created. - -An MPLS tunnel interface is an interface like any other and now ready -for use with the usual set of interface commands, e.g.: - -.. code-block:: console - - $ set interface state mpls-tunnel0 up - $ set interface ip address mpls-tunnel0 192.168.1.1/30 - $ ip route 1.1.1.1/32 via mpls-tunnel0 |