The SRv6 END.DTM Segment TypeJuniper NetworksEmbassy Business ParkBangaloreKA560093Indiashraddha@juniper.netJuniper NetworksHerndon20171VirginiaUSArbonica@juniper.netZTE CorporationPeoples Republic of Chinapeng.shaofu@zte.com.cnZTE CorporationUSAgregimirsky@gmail.comZTE CorporationPeoples Republic of Chinazhang.zheng@zte.com.cn
Routing Area
SPRING Working GroupSegment RoutingIPv6This document describes a new SRv6 segment type, called END.DTM. The
END.DTM segment type supports inter-working between SRv6 and SR-MPLS.
Like any segment type, END.DTM contains a function and arguments. The
function causes the processing SRv6 node to remove an SRv6 header and
impose an SR-MPLS label stack. The arguments determine MPLS-label stack
contents.Segment Routing (SR) allows source
nodes to steer packets through SR paths. It can be implemented over
IPv6 or MPLS
. When SR is implemented over IPv6, it is called SRv6. When SR
is implemented over MPLS, it is called SR-MPLS.This document describes a new SRv6 segment type, called END.DTM. The
END.DTM segment type supports inter-working between SRv6 and SR-MPLS.
Like any segment type, END.DTM contains a function and arguments. The
function causes the processing SRv6 node to:Remove an SRv6 header (i.e., an IPv6 header and its
extensions).Impose an SR-MPLS label stack.The arguments determine MPLS-label stack contents and Transport
Class of the MPLS Tunnel.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only
when, they appear in all capitals, as shown here. depicts an inter-working SR path. The SR
path originates on Node 1 and terminates on Node 5. It contains:An SRv6 partAn SR-MPLS partThe SRv6 part includes Nodes 1, 2 and 3. These nodes MUST be
SRv6-capable but are NOT REQUIRED to be SR-MPLS capable. An END.DTM
segment is instantiated on Node 3. Therefore, Node 3 MUST be able to
push an SR-MPLS label stack. However, it is NOT REQUIRED to process
incoming MPLS labels.The SRv6 part also includes:Segment A - An END segment that is instantiated on Node 2.Segment B - An END.DTM segment that is instantiated on Node
3.The SR-MPLS part includes Nodes 4 and 5. These nodes MUST be
SR-MPLS-capable but are NOT REQUIRED to be SRv6 capable.The SR-MPLS part also includes:Segment C - A prefix segment that is instantiated on Node 4.Segment D - A prefix segment that is instantiated on Node 5.The following paragraphs describe how a packet traverses this
inter-working SR path:Node 1 encapsulates the packet in an SRv6 header. The SRv6 header
contains the following Segment Identifiers (SID):A SID representing Segment A, encoded in the Destination Address
field of the IPv6 header.A SID representing Segment B, encoded in a Segment Routing Header (SRH).Node 1 sends the packet to Node 2. When the packet arrives at
Node 2, The Destination Address field in the IPv6 header represents a
locally instantiated END SID. Node 2 processes the packet as
follows:Decrement the Segments Left field in the SRHCopy the next SID from the SRH to the Destination Address field
of the IPv6 header.Forward the packet to Node 3.When the packet arrives at Node 3, The Destination Address
field in the IPv6 header represents a locally instantiated END.DTM SID.
Node 3 processes the packet as follows:Remove the IPv6 header and its extension headers (including the
SRH).Push two SR-MPLS labels, representing Segments D and C.Forward the packet to Node 4.When the packet arrives at Node 4, it is encapsulated in an
SR-MPLS label stack. Node 4 processes the packet as described in SR-MPLS.The End.DTM SID MUST be the last segment in a SR Policy. A SID
instance is associated with:An SR-MPLS label stack.An outbound interface.When Node N receives a packet destined to S and S is a locally
instantiated End.DTM SID, Node N executes the following procedure:IANA is requested to add the following entry to the "SRv6 Endpoint
Behaviors" sub-registry of the "Segment Routing Parameters"
registry:ValueHexEndpoint behaviorReferenceTBDTBDEND.DTM[This.ID]Because SR inter-working requires co-operation between inter-working
domains, this document introduces no security consideration beyond those
addressed in , and
.TBD