Carrying Virtual Transport Network
Identifier in IPv6 Extension HeaderHuawei TechnologiesHuawei Campus, No. 156 Beiqing RoadBeijing100095Chinajie.dong@huawei.comHuawei TechnologiesHuawei Campus, No. 156 Beiqing RoadBeijing100095Chinalizhenbin@huawei.comChina TelecomChina Telecom Beijing Information Science & Technology,
BeiqijiaBeijing102209Chinaxiechf@chinatelecom.cnChina TelecomChina Telecom Beijing Information Science & Technology,
BeiqijiaBeijing102209Chinamachh@chinatelecom.cnThis document proposes a new option type to carry virtual transport
network identifier (VTN ID) in the IPv6 extensions headers to identify
the Virtual Transport Network (VTN) the packet belongs to. The procedure
of processing the VTN option is also specified. This provides a scalable
solution for data plane encapsulation of enhanced VPN (VPN+) as
described in I-D.ietf-teas-enhanced-vpn. One typical use case of VPN+ is
to provide transport network slicing in 5G, while it could also be used
in more general cases.Virtual private networks (VPNs) have served the industry well as a
means of providing different groups of users with logically isolated
connectivity over a common network. Some customers may request a
connectivity services with advanced characteristics such as complete
isolation from other services or guaranteed performance. These services
are "enhanced VPNs" (known as VPN+). describes the framework and
candidate component technologies for providing enhanced VPN services.
One typical use case of VPN+ is to provide transport network slicing in
5G, while it could also be used in more general cases.The enhanced properties of VPN+ require tighter coordination and
integration between the underlay network resources and the overlay
network. VPN+ service is built on a Virtual Transport Network (VTN)
which has a customized network topology and a set of dedicated or shared
network resources allocated from the underlay network. The overlay VPN
together with the corresponding VTN in the underlay provide the VPN+
service. In the network, traffic of different VPN+ services need to be
processed separately based on the topology and the network resources
associated with the corresponding VTN. describes
the scalability considerations of enhanced VPN, in which one approach to
improve the data plane scalability is to introduce a dedicated
identifier indata packet to identify the VTN the packet belongs to, so
as to perform resource specific packet processing. This is called
Resource Independent (RI) VTN.This document proposes a mechanism to carry the VTN Identifier (VTN
ID) in the IPv6 extensions headers of packet,
so that the packet will be processed by network nodes using the network
resources allocated to the corresponding VTN. The procedure of
processing the VTN ID is also specified. This provides a scalable
solution for enhanced VPN data plane, so that it could be used to
support a large number of transport network slices in IPv6 network.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 BCP14
RFC 2119RFC
8174 when, and only when, they appear in all capitals, as shown
here.A new option type of IPv6 extension headers is defined to carry the
Virtual Transport Network Identifier (VTN ID) in IPv6 packet header. Its
format is shown as below:Option Type: 8-bit identifier of the type of option. The type of VTN
option is TBD by IANA. The highest-order bits of the type field are
defined as below:BB 00 The highest-order 2 bits are set to 00 to indicate that a
node which does not recognize this type will skip over it and
continue processing the header.C 0 The third highest-order bit are set to 0 to indicate this
option does not change en route.Opt Data Len: 8-bit unsigned integer indicates the length of the
option Data field of this option, in octets. The value of Opt Data Len
of VTN option SHOULD be set to 4.Option Data: 4-octet VTN which uniquely identifies a virtual
transport network.Editor's note: The length of the VTN ID is defined as 4-octet
partially for the matching with the 4-octet network slice identifier
defined in 3GPP .When an ingress node of an IPv6 or SRv6 domain receives a packet,
according to traffic classification or mapping policy, the packet
SHOULD be encapsulated in an outer IP header, and the VTN-ID of the
virtual transport network which the traffic is mapped to SHOULD be
carried in the extension header associated with the outer IPv6 header
. The ingress node MAY also encapsulate the SRH as defined in in the Routing Header of the outer IPv6 header.In order to make the VTN option be processed by each node along the
path, it is RECOMMENDED that the VTN option be carried in IPv6
extension headers which can be processed hop-by-hop in forwarding
plane. It can be carried in either the Hop-by-Hop Options header, or
some new extension headers which can be processed on each hop along
the path.On receipt of a packet with the VTN option, each network node which
can parse the VTN option SHOULD use the VTN ID to identify the virtual
network the packet belongs to. This means the forwarding behavior is
based on both the destination IP address and the VTN option.The
destination IP address is used for the lookup of the next-hop node,
and VTN-ID can be used to determine the set of network resources
reserved for processing and sending the packet to the next-hop node.
The domain egress node SHOULD decapsulate the outer IPv6 header.There can be different implementations of reserving local network
resources to the VTNs. On each interface, the resources allocated to a
particular VTN can be seen as a virtual sub-interface with dedicated
bandwidth and other associated resources. In packet forwarding, the
IPv6 destination address of the received packet is used to identify
the next-hop and the outgoing interface, and the VTN ID is used to
further identify the virtual sub-interface which is associated with
the VTN on the outgoing interface.Routers which do not support Hop-by-Hop options header SHOULD
ignore the Hop-by-Hop options header and forward the packet merely
based on the destination IP address. Routers which support Hop-by-Hop
Options, but do not recognize the VTN option SHOULD ignore the option
and continue to forward the packet merely based on the destination IP
address.As described in , nodes may be configured to
ignore the Hop-by-Hop Options header, and the packets containing a
Hop-by-Hop Options header may be dropped or assigned to a slow
processing path. When VTN option is carried in Hop-by-Hop option header,
operator needs to make sure that all the network nodes involved in the
VTN can either process the Hop-by-Hop Options header in packet
forwarding, or ignore the Hop-by-Hop Option header but continue to
forward the packet based on other fields and headers. In other words,
Packet mapping to a VTN MUST NOT be dropped due to the existence of the
Hop-by-Hop Options header. It is RECOMMENDED to configure the nodes to
process the Hop-by-Hop Option header if there is a nob for this.This document requests IANA to assign a new option type from
"Destination Options and Hop-by-Hop Options" registry.TBDThe authors would like to thank Juhua Xu for his review and valuable
comments.3GPP TS23.501