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diff --git a/src/vnet/srv6/sr_doc.rst b/src/vnet/srv6/sr_doc.rst new file mode 100644 index 00000000000..24501832b85 --- /dev/null +++ b/src/vnet/srv6/sr_doc.rst @@ -0,0 +1,123 @@ +.. _srv6_doc: + +SRv6: Segment Routing for IPv6 +============================== + +This is a memo intended to contain documentation of the VPP SRv6 +implementation. Everything that is not directly obvious should come +here. For any feedback on content that should be explained please +mailto:pcamaril@cisco.com + +Segment Routing +--------------- + +Segment routing is a network technology focused on addressing the +limitations of existing IP and Multiprotocol Label Switching (MPLS) +networks in terms of simplicity, scale, and ease of operation. It is a +foundation for application engineered routing as it prepares the +networks for new business models where applications can control the +network behavior. + +Segment routing seeks the right balance between distributed intelligence +and centralized optimization and programming. It was built for the +software-defined networking (SDN) era. + +Segment routing enhances packet forwarding behavior by enabling a +network to transport unicast packets through a specific forwarding path, +different from the normal path that a packet usually takes (IGP shortest +path or BGP best path). This capability benefits many use cases, and one +can build those specific paths based on application requirements. + +Segment routing uses the source routing paradigm. A node, usually a +router but also a switch, a trusted server, or a virtual forwarder +running on a hypervisor, steers a packet through an ordered list of +instructions, called segments. A segment can represent any instruction, +topological or service-based. A segment can have a local semantic to a +segment-routing node or global within a segment-routing network. Segment +routing allows an operator to enforce a flow through any topological +path and service chain while maintaining per-flow state only at the +ingress node to the segment-routing network. Segment routing also +supports equal-cost multipath (ECMP) by design. + +Segment routing can operate with either an MPLS or an IPv6 data plane. +All the currently available MPLS services, such as Layer 3 VPN (L3VPN), +L2VPN (Virtual Private Wire Service [VPWS], Virtual Private LAN Services +[VPLS], Ethernet VPN [E-VPN], and Provider Backbone Bridging Ethernet +VPN [PBB-EVPN]), can run on top of a segment-routing transport network. + +**The implementation of Segment Routing in VPP covers both the IPv6 data +plane (SRv6) as well as the MPLS data plane (SR-MPLS). This page +contains the SRv6 documentation.** + +Segment Routing terminology +--------------------------- + +- Segment Routing Header (SRH): IPv6 routing extension header of type + ‘Segment Routing’. (draft-ietf-6man-segment-routing-header-05) +- SegmentID (SID): is an IPv6 address. +- Segment List (SL) (SID List): is the sequence of SIDs that the packet + will traverse. +- SR Policy: defines the SRH that will be applied to a packet. A packet + steered into an SR policy may either receive the SRH by IPv6 header + encapsulation (as recommended in draft-ietf-6man-rfc2460bis) or it + could be inserted within an existing IPv6 header. An SR policy is + uniquely identified by its Binding SID and associated with a weighted + set of Segment Lists. In case several SID lists are defined, traffic + steered into the policy is unevenly load-balanced among them + according to their respective weights. +- Local SID: is a SID associated with a processing function on the + local node, which may go from advancing to the next SID in the SRH, + to complex user-defined behaviors. When a FIB lookup, either in the + main FIB or in a specific VRF, returns a match on a local SID, the + associated function is performed. +- BindingSID: a BindingSID is a SID (only one) associated one-one with + an SR Policy. If a packet arrives with an IPv6 DA corresponding to a + BindingSID, then the SR policy will be applied to such packet. + +SRv6 Features in VPP +-------------------- + +The SRv6 Network Programming +(*draft-filsfils-spring-srv6-network-programming*) defines the SRv6 +architecture. + +VPP supports the following SRv6 LocalSID functions: End, End.X, End.DX6, +End.DT6, End.DX4, End.DT4, End.DX2, End.B6, End.B6.Encaps. + +For further information and how to configure each specific function: +:ref:`srv6_localsid_doc` + +The Segment Routing Policy +(*draft-filsfils-spring-segment-routing-policy*) defines SR Policies. + +VPP supports SRv6 Policies with T.Insert and T.Encaps behaviors. + +For further information on how to create SR Policies: :ref:`srv6_policy_doc` + +For further information on how to steer traffic into SR Policies: +:ref:`srv6_steering_doc` + +SRv6 LocalSID development framework +----------------------------------- + +One of the *‘key’* concepts about SRv6 is network programmability. This +is why an SRv6 LocalSID is associated with an specific function. + +However, the true way to enable network programmability is allowing +any developer **easily** create his own SRv6 LocalSID function. That is +the reason why we have added some API calls such that any developer can +code his own SRv6 LocalSID behaviors as plugins an add them to the +running SRv6 code. + +The principle is that the developer only codes the behavior -the graph +node-. However all the FIB handling, SR LocalSID instantiation and so on +are done by the VPP SRv6 code. + +For more information please refer to: :ref:`srv6_plugin_doc` + +Available SRv6 plugins include: + +- :ref:`srv6_as_plugin_doc` +- :ref:`srv6_ad_plugin_doc` +- :ref:`srv6_am_plugin_doc` +- :ref:`srv6_mobile_plugin_doc` |