Unified Identifier in IPv6 Segment Routing NetworksZTE Corp.gregimirsky@gmail.comZTE CorporationNo.50 Software Avenue, Yuhuatai DistrictNanjingChinapeng.shaofu@zte.com.cn
Routing
NetworkInternet-DraftSegment RoutingSID
Segment Routing architecture leverages the paradigm of source routing. It
can be realized in a network data plane by prepending the packet with a list of instructions, a.k.a. segments.
A segment can be encoded as a Multi-Protocol Label Switching (MPLS) label, IPv4 address or IPv6 address.
Segment Routing can be applied in MPLS data plane by encoding segments in MPLS label stack. It also
can be applied to IPv6 data plane by encoding list of segment identifiers in IPv6 Segment Routing Extension Header (SRH).
This document extends the use of the SRH to segment identifiers encoded as MPLS label and IPv4 address.
Segment Routing architecture leverages the paradigm of source routing. It
can be realized in a network data plane by prepending the packet with a list of instructions, a.k.a. segment identifiers (SIDs).
A segment can be encoded as a Multi-Protocol Label Switching (MPLS) label, IPv4 address or IPv6 address.
Segment Routing can be applied in MPLS data plane by encoding 20-bits SIDs in MPLS
label stack . It also
can be applied to IPv6 data plane by encoding list of 128-bits SIDs
in IPv6 Segment Routing Extension Header (SRH) .
Applicability of 32-bits SID that may represent an IPv4 address has not been defined.
SR extensions to Interior Gateway Protocols (IGP), IS-IS ,
OSPF , and OSPFv3 ,
defined how 20-bits and 32-bits SIDs advertised and bound to SR objects and/or instructions.
Extensions to BGP link-state address family enabled propagation of
segment information of variable length via BGP.
This document extends the use of the SRH
to SIDs encoded as MPLS label and IPv4 address.
SR: Segment RoutingSRH: Segment Routing Extension HeaderMPLS: Multiprotocol Label SwitchingMPLS-SR: Segment Routing in MPLSSID: Segment IdentifierIGP: Interior Gateway ProtocolOAM: Operation, Administration and MaintenanceTE: Traffic EngineeringSRv6: Segment Routing in IPv6
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.
Many functions related to Operation, Administration and Maintenance (OAM) require identification of
the SR tunnel ingress and the path, constructed by segments, between the ingress and the egress SR nodes.
Combination of IPv6 encapsulation and SRH ,
referred to as SRv6,
comply with this requirements while it is challenging when applying SR in MPLS networks, also referred to as MPLS-SR.
On the other hand, the size of IPv6 SID presents a scaling challenge to use topological instructions
that define strict explicit traffic engineered (TE) path in combination with
service-based instructions. At the same time, that is where MPLS-SR approach provides
better results due to smaller SID length.
addresses the scaling challenge by
using more compact SID encoding of MPLS-SR. Ability to address OAM challenge characteristic
to MPLS-SR is open for investigation.
In section 3 of SRH format has been defined
as presented in
This document defines the new field Size in the Flags field, presented in ,
as a two-bits field with the following values:
0b00 - 128-bits SID;0b01 - 20-bits SID;0b10 - 32-bits SID0b11 - reserved for future use.
When the value of the S field is 0b01, the 20-bit SID is encoded in four octets and
occupies the 20 rightmost bits.
Entries of the segment list in the SRH MUST be of the same length.
When the SRH is used to include 20-bits or 32-bits SIDs the ingress and transit nodes of an SR tunnel
act as described in Section 5.1 and Section 5.2 of
respectively.
TBD
TBD
This specification inherits all security considerations of
and .
TBD