Genralized IPv6 Tunnel for MPLSHuawei156 Beiqing RoadBeijing, 100095P.R. Chinalizhenbin@huawei.comHuawei156 Beiqing RoadBeijing,100095P.R. Chinachenshuanglong@huawei.comHuawei156 Beiqing RoadBeijing,100095P.R. Chinagaoqiangzhou@huawei.comChina UnicomBeijing,100048P.R. Chinazhangs366@chinaunicom.cnWith the development of new services, MPLS faces many problems and
technical challenges. This document defines the method to implement MPLS
through the GIP6 tunnel.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in .The GIP6 tunnel is defined in [draft-li-rtgwg-generic-ipv6-tunnel-00]
which is to solve the challenges of the existing IP tunnels to support
new features such as alternate marking, IOAM, network resource partition
and APN.With the development of new services, MPLS also faces many problems
and technical challenges. For example, it is difficult to encapsulate
new forwarding attributes because of lack of the metadata extensibility.
This document defines how to implement MPLS through the GIP6 tunnel
which is to solve the possible problems effectively.APN: Application-Aware NetworkingGIP6: Generic Ipv6 TunnelGRE: Generic Routing EncapsulationIFIT: In-situ Flow Information TelemetryMP2P: Multi Point To PointMPLS: Multiprotocol Label SwitchingPM: Performance MonitorSFL: Synonymos Flow LabelsSR-MPLS: Segment Routing Multiprotocol Label SwitchingVXLAN: Virtual eXtensible Local Area NetworkWith the development of new services, MPLS faces the following the
technical problems and challenges of MPLS:1. MPLS is lack of the source indication and MP2P connections may
occur. This causes the difficulty and complex process for OAM over MPLS.
Although SFL() is defined, there is few
implementation.2. The payload type (for example, L2 or L3 packets) cannot be
directly determined because there is no payload indication.3. There is no metadata extensibility and it is difficult to
encapsulate new forwarding attributes for the new features such as IETF
network slicing, IFIT, and APN.4. The process of the ECMP function is complex and affects forwarding
performance. Entropy labels or flow labels are placed at the bottom of
the label stack for processing and the internal IP header information
may have to be parsed for the purpose of ECMP. defines the
GIP6 tunnel to support both new features and the existing functions for
the IP tunnels based on the extension of the IPv6 extension header. If
the GIP6 tunnel is used for MPLS, there can be the following
advantages:1. The IPv6 source address is used to form a source identifier.2. The IPv6 NH can indicate the payload type.3. IPv6 flow labels are used to implement ECMP.4. The encapsulations for the new features have been defined well in
the IPv6 and can be reused easily.It is simple and can benefit forwarding performance. Moreover, there
have been many implementations and deployments.In order to support MPLS based on the GIP6 tunnel, the method to
carry MPLS label stack information is defined as follows:1. A special IPv6 prefix MUST be used to indicate that it is followed
by MPLS label encapsulation. The special IPv6 prefix can be specified or
a well-known IPv6 prefix to be assigned.2. The IPv6 special prefix can be followed by multiple MPLS label
encapsulations to form a 128-bit IPv6 MPLS SID (Type 1). The format of
the IPv6 MPLS SID (Type 1) is shown in the following figure.Special prefix: TBDMPLS Label Encap: For details, please refer to section 2.1 in .3. IPv6 MPLS SID (Type 1) can be placed in the IPv6 destination
address.Processing of the first label following the special prefix is as
follows:(1) If the local action of the MPLS label is POP, the followed label
encapsulations are shifted left by 32 bits after the label is popped.
The following figure shows the process.(2) If the local action of the MPLS label is SWAP, the label
encapsulation is changed to the new label after swap.4. If all the MPLS label stack cannot be placed in the IPv6
destination address, IPv6 RH can be used to house the remaining MPLS
label stack.(1) IPv6 MPLS SID (Type 2) is defined to house multiple (<= 4)
label encapsulations. The format of the IPv6 MPLS SID (Type 2) is shown
in the following figure.MPLS Label Encap: For details, see section 2.1 in .(2) IPv6 MPLS SID (Type 2) is used as the segment in the RH. After
all of the label encapsulations in the IPv6 destination address are
popped, the first label encapsulation in the segment indicated by the SL
of the RH will be processed as follows:-- If the local action of the MPLS label is POP, the followed label
encapsulations are shifted left by 32 bits after the label is
popped.-- If the local action of the MPLS label is SWAP, the label
encapsulation is changed to the new label after swap.After all the label encapsulations in the segment are popped, SL
minus 1. Then the first label encapsulation in the segment indicted by
the new SL will go on to be processed as the above procedures.A new type of RH can be defined to contain IPv6 MPLS SID (Type 2) or
SRv6 SRH can be reused for the purpose.5. When find the S flag of the label encapsulation in the IPv6
destination address or the RH to be processed is set, this means the
bottom of the label stack is reached and the process of the label stack
in the GIP6 will end after the label is popped.If an intermediate node requires to push a label or a label stack,
there can be two modes: Encap mode and Inserting mode.1) Encap mode: with this mode, a new IPv6 MPLS packet header is
encapsulated outside the original MPLS packet, and the MPLS label
(stack) is encapsulated in the new IPv6 MPLS packet header as the above
procedures.2) Inserting mode: All the label encapsulations in the IPv6
destination address and the IPv6 RH (if exist) need to be shifted right
and the new label (stack) can be placed immediately following the
special prefix in the IPv6 destination address. The process is complex
and not recommended.GIP6 only provides a way to carry MPLS label encapsulations in the
data plane. The existing MPLS control plane does not need to be changed.
That is, MPLS labels on the control plane can still be distributed for
IPv4, IPv6, L2, etc.TBD.Jie DongHuawei Technologiesjie.dong@huawei.comTBD.