Internet DRAFT - draft-ietf-6man-enhanced-vpn-vtn-id
draft-ietf-6man-enhanced-vpn-vtn-id
Network Working Group J. Dong
Internet-Draft Z. Li
Intended status: Standards Track Huawei Technologies
Expires: 14 September 2023 C. Xie
C. Ma
China Telecom
G. Mishra
Verizon Inc.
13 March 2023
Carrying Virtual Transport Network (VTN) Information in IPv6 Extension
Header
draft-ietf-6man-enhanced-vpn-vtn-id-03
Abstract
Virtual Private Networks (VPNs) provide different customers with
logically separated connectivity over a common network
infrastructure. With the introduction and evolvement of 5G and other
network scenarios, some existing or new customers may require
connectivity services with advanced characteristics comparing to
traditional VPNs. Such kind of network service is called enhanced
VPNs (VPN+). VPN+ can be used to deliver IETF network slices, and
could also be used for other application scenarios.
A Virtual Transport Network (VTN) is a virtual underlay network which
consists of a set of dedicated or shared network resources allocated
from the physical underlay network, and is associated with a
customized logical network topology. VPN+ services can be delivered
by mapping one or a group of overlay VPNs to the appropriate VTNs as
the virtual underlay. In packet forwarding, some fields in the data
packet needs to be used to identify the VTN the packet belongs to, so
that the VTN-specific processing can be performed on each node the
packet traverses.
This document proposes a new Hop-by-Hop option of IPv6 extension
header to carry the VTN related information in data packets, which
could used to identify the VTN specific processing to be performed on
the packets. The procedure of processing the VTN option is also
specified.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. New IPv6 Extension Header Option for VTN . . . . . . . . . . 4
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Adding VTN Option to Packet . . . . . . . . . . . . . . . 6
3.2. VTN based Packet Forwarding . . . . . . . . . . . . . . . 6
4. Operational Considerations . . . . . . . . . . . . . . . . . 7
5. Considerations about Generalization . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
Virtual Private Networks (VPNs) provide different customers with
logically isolated connectivity over a common network infrastructure.
With the introduction and evolvement of 5G and other network
scenarios, some existing or new customers may require connectivity
services with advanced characteristics comparing to traditional VPNs,
such as resource isolation from other services or guaranteed
performance. Such kind of network service is called enhanced VPN
(VPN+). VPN+ service requires the coordination and integration
between the overlay VPNs and the capability and resources of the
underlay network. VPN+ can be used to deliver IETF network slices
[I-D.ietf-teas-ietf-network-slices].
[I-D.ietf-teas-enhanced-vpn] describes a framework and the candidate
component technologies for providing VPN+ services. It also
introduces the concept of Virtual Transport Network (VTN). A VTN is
a virtual underlay network which consists of a set of dedicated or
shared network resources allocated from the physical underlay
network, and is associated with a logical network topology. VPN+
services can be delivered by mapping one or a group of overlay VPNs
to the appropriate VTNs as the underlay, so as to provide the network
characteristics required by the customers. In packet forwarding,
traffic of different VPN+ services needs to be processed separately
based on the network resources and the logical topology associated
with the corresponding VTN. In the context of network slicing, VTN
and NRP are considered as similar concepts, and NRP can be seen as an
instantiation of VTN.
[I-D.ietf-teas-nrp-scalability] describes the scalability
considerations and the possible optimizations for providing a
relatively large number of VTNs for VPN+ services. One approach to
improve the data plane scalability of VTN is to introduce a dedicated
VTN Resource Identifier (VTN Resource ID) in the data packet to
identify the set of network resources allocated to a VTN, so that
VTN-specific packet processing can be performed using that set of
resources, which avoids the possible resource competition with
services in other VTNs. This is called Resource Independent (RI)
VTN. A VTN Resource ID represents a subset of the resources (e.g.
bandwidth, buffer and queuing resources) allocated on a given set of
links and nodes which constitute a logical network topology. The
logical topology associated with a VTN could be defined using
mechanisms such as Multi-Topology [RFC4915], [RFC5120] or Flex-Algo
[RFC9350], etc.
This document proposes a mechanism to carry the VTN related
information in a new Hop-by-Hop option called "VTN option" of IPv6
extension header [RFC8200] of IPv6 packet, so that on each network
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node along the packet forwarding path, the VTN option in the packet
is parsed, and the obtained VTN Resource ID is used to instruct the
network node to use the set of network resources allocated to the
corresponding VTN to process and forward the packet. The procedure
for processing the VTN option is also specified. This provides a
scalable solution to support a relatively large number of VTNs in an
IPv6 network.
Although the application of the VTN option in this document is to
carry the resource ID information, the VTN option is considered as a
generic mechanism to convey network wide identifiers with different
semantics to meet the possible use cases in the future.
1.1. Requirements Language
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. New IPv6 Extension Header Option for VTN
A new Hop-by-Hop option type "VTN" is defined to carry the VTN
related information in an IPv6 packet. Its format is shown as below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Context Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ VTN ID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. The format of VTN Option
Option Type: 8-bit identifier of the type of option. The type of VTN
option is to be assigned by IANA. The 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 is set to 0 to indicate this
option does not change en route.
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* TTTTT To be assigned by IANA.
Opt Data Len: 8-bit unsigned integer indicates the length of the
option Data field of this option, in octets.
Flags: 8-bit flags field. The most significant bit is defined in
this document.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|S|U U U U U U U|
+-+-+-+-+-+-+-+-+
* S (Strict Match): The S flag is used to indicate whether the VTN
ID MUST be strictly matched for the processing of the packet.
When S flag is set to 1, if the VTN ID in the VTN option does not
match with any of the VTN ID provisioned on the network node, the
packet MUST be dropped. When S flag is set to 0, if the VTN ID
does not match with any of the VTN ID provisioned on the the
network node, the packet SHOULD be forwarded using the default
behavior as if the VTN option does not exist.
* U (Unused): These flags are reserved for future use. They SHOULD
be set to 0 on transmission and MUST be ignored on receipt.
Context Type (CT): One-octet field used to indicate the semantics and
length of the VTN ID carried in the option. The context value
defined in this document are as follows:
* CT=0: The VTN ID is a 4-octet resource ID, which is used to
identify a subset of network resource on the involved network
nodes and links of a VTN.
Reserved: 2-octet field reserved for future use. They SHOULD be set
to 0 on transmission and MUST be ignored on receipt.
VTN ID: The identifier of a Virtual Transport Network, the semantics
and length of the ID is determined by the Context Type.
Note that, if a deployment found it useful, the four-octet VTN ID
field may be derived from the four-octet Single Network Slice
Selection Assistance Information (S-NSSAI) defined in 3GPP [TS23501].
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3. Procedures
As the VTN option needs to be processed by each node along the
forwarding path, it MUST be carried in IPv6 Hop-by-Hop Options
header. This section describes the procedures for VTN option
processing when the Context Type is set to 0. The procedures for VTN
option with other Context Types are out of the scope of this
document.
3.1. Adding VTN Option to Packet
When an ingress node of an IPv6 domain receives a packet, according
to the traffic classification or mapping policy, the packet is
steered into one of the VTNs in the network, then the packet MUST be
encapsulated in an outer IPv6 header, and the Resource ID of the VTN
which the packet is mapped to MUST be carried in the VTN option of
the Hop-by-Hop Options header, which is associated with the outer
IPv6 header.
3.2. VTN based Packet Forwarding
On receipt of a packet with the VTN option, each network node which
can process the VTN option in fast path MUST use the VTN Resource ID
to determine the set of local network resources allocated to the VTN
for packet processing. The packet forwarding behavior is based on
both the destination IP address and the VTN Resource ID. More
specifically, the destination IP address is used to determine the
next-hop and the outgoing interface, and VTN Resource ID is used to
determine the set of network resources on the outgoing interface
which are allocated to the VTN for processing and sending the packet.
If the VTN Resource ID does not match with any of the VTN Resource ID
provisioned on the outgoing interface, the S flag in the VTN option
is used to determine whether the packet is dropped or forwarded using
the default set of network resources of the outgoing interface. The
Traffic Class field of the outer IPv6 header MAY be used to provide
differentiated treatment for packets which belong to the same VTN.
The egress node of the IPv6 domain MUST decapsulate the outer IPv6
header and the Hop-by-Hop Options header which includes the VTN
option.
In the forwarding plane, there can be different approaches of
partitioning the local network resources and allocating them to
different VTNs. For example, on one physical interface, a subset of
the forwarding plane resources (e.g. bandwidth and the associated
buffer and queuing resources) can be allocated to a particular VTN
and represented as a virtual sub-interface with reserved bandwidth
resource. In packet forwarding, the IPv6 destination address of the
received packet is used to identify the next-hop and the outgoing
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layer-3 interface, and the VTN Resource ID is used to further
identify the virtual sub-interface on the outgoing interface which is
associated with the VTN.
Network nodes which do not support the processing of Hop-by-Hop
Options header SHOULD ignore the Hop-by-Hop options header and
forward the packet only based on the destination IP address. Network
nodes which support Hop-by-Hop Options header, but do not support the
VTN option SHOULD ignore the VTN option forward the packet only based
on the destination IP address. The network node MAY process the rest
of the Hop-by-Hop options in the Hop-by-Hop Options header.
4. Operational Considerations
As described in [RFC8200], network nodes may be configured to ignore
the Hop-by-Hop Options header, drop packets containing a Hop-by-Hop
Options header, or assign packets containing a Hop-by-Hop Options
header to a slow processing path. In networks with such network
nodes, it is important that packets of a VTN are not dropped due to
the existence of the Hop-by-Hop Options header. Operators need to
make sure that all the network nodes involved in a VTN can either
process the Hop-by-Hop Options header in the fast path, or ignore the
Hop-by-Hop Options header. Since a VTN is associated with a logical
network topology, it is practical to ensure that all the network
nodes involved in that logical topology support the processing of the
Hop-by-Hop Options header and the VTN option in the fast path, and
constrain the packet forwarding path to the logical topology of the
VTN.
[I-D.ietf-6man-hbh-processing] specifies the modified procedures for
the processing of IPv6 Hop-by-Hop Options header, with the purpose of
making the Hop-by-Hop Options header useful. Network nodes complying
with [I-D.ietf-6man-hbh-processing] will not drop packets with Hop-
by-Hop Options header and the VTN option.
5. Considerations about Generalization
During the discussion of this document in the 6MAN WG, one of the
suggestions received is to make the VTN option more generic in terms
of semantics and encoding. This section gives some analysis about to
what extent the semantics of VTN could be generalized, and how the
generalization could be achieved with the proposed encoding.
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Based on the VTN definition in [I-D.ietf-teas-enhanced-vpn], the
concept of VTN could be extended as: a virtual transport network
which is associated with a set of network-wide attributes and states
maintained on each participating network node. The attributes
associated with an VTN may include but not limited to: network
resource attributes, network topology attributes, and network
function attributes etc.
* The network resource can refer to various type of data plane
resources, including link bandwidth, bufferage and queueing
resources.
* The network topology can be multipoint-to-multipoint, point-to-
point, point-to-multipoint or multipoint-to-point.
* The network functions may include both data forwarding actions and
other types network functions which can be executed on data
packets mapped to a VTN.
This shows the semantics of VTN can be quite generic. Although
generalization is something good to have, it would be important to
understand and identify the boundary of generalization. In this
document, It is anticipated that for one network attribute to be
included in VTN, it needs to be a network-wide attribute rather than
a node-specific attribute. Thus whether a network-wide view can be
provided or not could be considered as one prerequisite of making one
attribute part of the VTN option.
The format of the VTN option contains the Flags field, the Context
Type field and the Reserved field, which provide the capability for
future extensions. That said, since the VTN option needs to be
processed by network nodes in the fast path, the capability of
network devices need to be considered when new semantics and encoding
are introduced.
6. IANA Considerations
This document requests IANA to assign a new option type from
"Destination Options and Hop-by-Hop Options" registry.
Value Description Reference
--------------------------------------------
TBA VTN Option this document
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7. Security Considerations
The security considerations with IPv6 Hop-by-Hop Options header are
described in [RFC8200], [RFC7045], [RFC9098] and
[I-D.ietf-6man-hbh-processing]. This document introduces a new IPv6
Hop-by-Hop option which is either processed in the fast path or
ignored by network nodes, thus it does not introduce additional
security issues.
8. Contributors
Zhibo Hu
Email: huzhibo@huawei.com
Lei Bao
Email: baolei7@huawei.com
9. Acknowledgements
The authors would like to thank Juhua Xu, James Guichard, Joel
Halpern, Tom Petch, Aijun Wang, Zhenqiang Li, Tom Herbert, Adrian
Farrel, Eric Vyncke and Erik Kline for their review and valuable
comments.
10. References
10.1. Normative References
[I-D.ietf-6man-hbh-processing]
Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
Processing Procedures", Work in Progress, Internet-Draft,
draft-ietf-6man-hbh-processing-05, 23 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
hbh-processing-05>.
[I-D.ietf-teas-enhanced-vpn]
Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
Framework for Enhanced Virtual Private Network (VPN+)",
Work in Progress, Internet-Draft, draft-ietf-teas-
enhanced-vpn-12, 23 January 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
enhanced-vpn-12>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
10.2. Informative References
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
K., Contreras, L. M., and J. Tantsura, "A Framework for
IETF Network Slices", Work in Progress, Internet-Draft,
draft-ietf-teas-ietf-network-slices-19, 21 January 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
ietf-network-slices-19>.
[I-D.ietf-teas-nrp-scalability]
Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J.,
Mishra, G. S., Qin, F., Saad, T., and V. P. Beeram,
"Scalability Considerations for Network Resource
Partition", Work in Progress, Internet-Draft, draft-ietf-
teas-nrp-scalability-01, 24 October 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
nrp-scalability-01>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013,
<https://www.rfc-editor.org/info/rfc7045>.
[RFC9098] Gont, F., Hilliard, N., Doering, G., Kumari, W., Huston,
G., and W. Liu, "Operational Implications of IPv6 Packets
with Extension Headers", RFC 9098, DOI 10.17487/RFC9098,
September 2021, <https://www.rfc-editor.org/info/rfc9098>.
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[RFC9099] Vyncke, É., Chittimaneni, K., Kaeo, M., and E. Rey,
"Operational Security Considerations for IPv6 Networks",
RFC 9099, DOI 10.17487/RFC9099, August 2021,
<https://www.rfc-editor.org/info/rfc9099>.
[RFC9350] Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
DOI 10.17487/RFC9350, February 2023,
<https://www.rfc-editor.org/info/rfc9350>.
[TS23501] "3GPP TS23.501", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
Authors' Addresses
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing
100095
China
Email: jie.dong@huawei.com
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing
100095
China
Email: lizhenbin@huawei.com
Chongfeng Xie
China Telecom
China Telecom Beijing Information Science & Technology, Beiqijia
Beijing
102209
China
Email: xiechf@chinatelecom.cn
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Chenhao Ma
China Telecom
China Telecom Beijing Information Science & Technology, Beiqijia
Beijing
102209
China
Email: machh@chinatelecom.cn
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
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