Network Working Group Z. Li
Internet-Draft J. Dong
Intended status: Standards Track Huawei Technologies
Expires: August 26, 2021 February 22, 2021
Carrying Virtual Transport Network Identifier in MPLS Packet
draft-li-mpls-enhanced-vpn-vtn-id-00
Abstract
A Virtual Transport Network (VTN) is a virtual network which has a
customized network topology and a set of dedicated or shared network
resources allocated from the underlying network infrastructure.
Multiple VTNs can be created by network operator for using as the
underlay for one or a group of VPNs services to provide enhanced VPN
(VPN+) services. 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 executed.
This document proposes a mechanism to carry the VTN-ID and the
associated information in an MPLS packet to identify the VTN the
packet belongs to. The procedure for processing the VTN ID is also
specified.
Status of This Memo
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This Internet-Draft will expire on August 26, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Carrying VTN Information in MPLS Packet . . . . . . . . . . . 3
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. VTN Header Insertion . . . . . . . . . . . . . . . . . . 5
4.2. VTN based Packet Forwarding . . . . . . . . . . . . . . . 5
5. Capability Advertisement and Negotiation . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Virtual Private Networks (VPNs) provide different groups of users
with logically isolated connectivity over a common shared network
infrastructure. With the introduction of 5G, new service types may
require connectivity services with advanced characteristics comparing
to traditional VPNs, such as strict isolation from other services or
guaranteed performance. These services are refered to as "enhanced
VPNs" (VPN+). [I-D.ietf-teas-enhanced-vpn] describes a framework and
candidate component technologies for providing VPN+ services.
The enhanced properties of VPN+ require integration between the
overlay connectivity and the characteristics provided by the underlay
network. To meet the requirement of enhanced VPN services, a number
of Virtual Transport Networks (VTNs) need to be created, each
consists of a subset of the underlay network topology and a set of
network resources allocated from the underlay network to meet the
requirement of one or a group of VPN+ services. In the network,
traffic of different VPN+ services may to be processed separately
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based on the topology and the network resources associated with the
corresponding VTN.
For network scenraios where a large number of VTNs need to be created
and maintained, [I-D.dong-teas-enhanced-vpn-vtn-scalability]
describes the scalability considerations for VTN. One approach to
improve the data plane scalability is introducing a dedicated VTN
Identifier (VTN-ID) in data packets to identify the VTN the packets
belong to, so that VTN-specific packet processing can be performed by
network nodes.
This document proposes a mechanism to carry the VTN Identifier (VTN-
ID) and the related information in MPLS [RFC3031] data packets, so
that the packet will be processed by network nodes using the set of
network resources allocated to the corresponding VTN. The procedure
for processing the VTN-ID is also specified. The forwarding path of
the MPLS LSP is determined using the MPLS label stack in the packet,
and the set of local network resources used for processing the packet
is determined by the VTN-ID. The mechanism introduced in this
document is applicable to both MPLS networks with RSVP-TE [RFC3209]
or LDP [RFC5036] based LSPs, and MPLS networks with Segment Routing
(SR) [RFC8402] [RFC8660].
2. 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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
3. Carrying VTN Information in MPLS Packet
This document defines a new VTN header which is used to carry the
VTN-ID and other VTN related information. In an MPLS packet, The VTN
header follows the MPLS label stack, and precedes the header and
payloads in the upper layer. The format of VTN header is shown as
below:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Nibble | Length| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VTN Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Service Differentiator (Optional) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. The format of MPLS VTN Header
Where:
o Nibble: The first 4-bit field is set to the binary value 0010.
This is to ensure that the VTN header will not be interpreted as
an IP header or the ACH of pseudowire packet.
o Length: Indicate the length of the MPLS VTN header in 32-bit
words.
o Flags: 8-bit Flags field. All the flags are reversed for future
use. This field SHOULD be set to zero on transmission and MUST be
ignored on receipt.
o Reserved: 16-bit field reserved for future use.
o VTN Identifier (VTN-ID): A 4-octet global significant identifier
which uniquely identifies a VTN.
o Service Differentiator: A variable length field to identify a
service instance which is carried by the VTN. In the context of
5G network slicing, this may be the Single Network Slice Selection
Assistance Information (S-NSSAI) associated with the packet.
Editor's note: The length of the VTN-ID is defined as 4-octet for the
potential matching or mapping with the 4-octet S-NSSAI defined in
3GPP [TS23501] for 5G network slicing. One or multiple S-NSSAIs may
be mapped to one VTN.
8-bit 24-bit
+------------+-------------------------+
| SST | Slice Differentiator |
+------------+-------------------------+
Figure 2. The format of S-NSSAI
A new MPLS special-purpose label or extended special-purpose label
[RFC7274] is defined as the VTN Header Indicator (VHI), its value is
to be assigned by IANA. The VHI label is used to indicate the
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existence of the VTN Header after the MPLS label stack in the packet.
The position of the VHI label in the MPLS label stack is not limited.
The benefit of introducing the MPLS VTN header to carry the VTN-ID
and the related information is that it provides the flexibility to
encode information which cannot be accommodated in an MPLS label
(20-bit), and the length of the header can be variable.
4. Procedures
4.1. VTN Header Insertion
When the ingress node of an LSP receives a packet, according to
traffic classification or mapping policy, the packet is steered into
one of the VTNs in the network, then a VTN header SHOULD be inserted
into the packet, and the VTN-ID which the packet is mapped to SHOULD
be carried in the VTN header. The ingress node may also insert a
Service Differentiator into the VTN header to further identify the
service instance the packet belongs to.The ingress node SHOULD also
encapsulates the packet with an MPLS label stack which are used to
determine the path traversed by the LSP. The VHI label SHOULD be
inserted in the label stack to identify the existence of the VTH
header.
4.2. VTN based Packet Forwarding
On receipt of a MPLS packet which carries the VHL and the VTN header,
network nodes which support the mechanism defined in this document
SHOULD scan the label stack to figure out the existence of the VHL.
If there is a VHL in the label stack, then the network node SHOULD
parse the VTN header and use the VTN-ID to identify the VTN the
packet belongs to, and use the local resources allocated to the VTN
to process and forward the packet. The forwarding behavior is based
on both the top MPLS label and the VTN ID. The top MPLS label is
used for the lookup of the next-hop, and the VTN-ID can be used to
determine the set of network resources allocated by the network nodes
for processing and sending the packet to the next-hop. The network
node may further use the Service Differentiator information to
provide some fine-grained differentiation and processing based on the
local network resources allocated to the VTN.
There can be different approaches used for allocating network
resources on each network node to the VTNs. For example, on one
interface, a subset of forwarding plane resource (e.g. bandwidth and
the associated buffer/queuing/scheduling resources) allocated to a
particular VTN can be considered as a virtual layer-2 sub-interface
with dedicated bandwidth and the associated resources. In packet
forwarding, the top MPLS label of the received packet is used to
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identify the next-hop and the outgoing Layer 3 interface, and the
VTN-ID is used to further identify the virtual sub-interface which is
associated with the VTN on the outgoing interface.
Network nodes which do not support the mechanism in this document
SHOULD ignore the VHL and the VTN header, and forward the packet only
based on the top MPLS label.
The egress node of the MPLS LSP SHOULD pop the VHL together with
other LSP labels, and decapsulate the VTN header.
5. Capability Advertisement and Negotiation
Before inserting the VTN header into an MPLS packet, the ingress node
MAY need to know whether the nodes along the LSP can process the VTN
header properly according to the mechanisms defined in this document.
This can be achieved by introducing the capability advertisement and
negotiation mechanism for the VTN header. The ingress node also need
to know whether the egress node of the LSP can remove the VTN header
properly before parsing the upper layer and send the packet to the
next hop. The capability advertisement and negotiation mechanism
will be described in a future version of this document.
6. IANA Considerations
This document requests IANA to assign a new special-purpose label
from the "Special-Purpose MPLS Label Values" or the "Extended
Special-Purpose MPLS Label Values" registry.
Value Description Reference
-------------------------------------------------
TBD VTN Header Indicator this document
7. Security Considerations
TBD
8. Contributors
Zhibo Hu
Email: huzhibo@huawei.com
9. Acknowledgements
TBD.
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10. References
10.1. Normative References
[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>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
and Retiring Special-Purpose MPLS Labels", RFC 7274,
DOI 10.17487/RFC7274, June 2014,
<https://www.rfc-editor.org/info/rfc7274>.
[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>.
10.2. Informative References
[I-D.dong-teas-enhanced-vpn-vtn-scalability]
Dong, J., Li, Z., Qin, F., and G. Yang, "Scalability
Considerations for Enhanced VPN (VPN+)", draft-dong-teas-
enhanced-vpn-vtn-scalability-01 (work in progress),
November 2020.
[I-D.ietf-teas-enhanced-vpn]
Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
Framework for Enhanced Virtual Private Networks (VPN+)
Service", draft-ietf-teas-enhanced-vpn-06 (work in
progress), July 2020.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <https://www.rfc-editor.org/info/rfc5036>.
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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[TS23501] "3GPP TS23.501", 2016,
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.
Authors' Addresses
Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: lizhenbin@huawei.com
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: jie.dong@huawei.com
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