Network working group X. Xu
Internet Draft Huawei
Category: Standard Track N. Sheth
Juniper
L. Yong
Huawei
C. Pignataro
Cisco
Y. Fan
China Telecom
Expires: December 2013 June 9, 2013
Encapsulating MPLS in UDP
draft-ietf-mpls-in-udp-02
Abstract
Existing technologies to encapsulate Multi-Protocol Label Switching
(MPLS) over IP are not adequate for efficient load balancing of MPLS
application traffic, such as MPLS-based Layer2 Virtual Private
Network (L2VPN) or Layer3 Virtual Private Network (L3VPN) traffic
across IP networks. This document specifies additional IP-based
encapsulation technology, referred to as MPLS-in-User Datagram
Protocol (UDP), which can facilitate the load balancing of MPLS
application traffic across IP networks.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 9, 2013.
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Copyright Notice
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Conventions used in this document
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 RFC-2119 [RFC2119].
Table of Contents
1. Introduction ................................................ 3
1.1. Existing Technologies .................................. 3
1.2. Motivations for MPLS-in-UDP Encapsulation .............. 4
2. Terminology ................................................. 4
3. Encapsulation in UDP ........................................ 4
4. Processing Procedures ....................................... 5
5. Applicability ............................................... 6
6. Security Considerations ..................................... 6
7. IANA Considerations ......................................... 6
8. Acknowledgements ............................................ 6
9. References .................................................. 7
9.1. Normative References ................................... 7
9.2. Informative References ................................. 7
Authors' Addresses ............................................. 8
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1. Introduction
To fully utilize the bandwidth available in IP networks and/or
facilitate recovery from a link or node failure, load balancing of
traffic over Equal Cost Multi-Path (ECMP) and/or Link Aggregation
Group (LAG) across IP networks is widely used. In effect, most
existing core routers in IP networks are already capable of
distributing IP traffic flows over ECMP paths and/or LAG based on the
hash of the five-tuple of User Datagram Protocol (UDP)[RFC768] and
Transmission Control Protocol (TCP) packets (i.e., source IP address,
destination IP address, source port, destination port, and protocol).
In practice, there are some scenarios for Multi-Protocol Label
Switching (MPLS) applications (e.g., MPLS-based Layer2 Virtual
Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN))
where the MPLS application traffic needs to be transported through
IP-based tunnels, rather than MPLS tunnels. For example, MPLS-based
L2VPN or L3VPN technologies may be used for interconnecting
geographically dispersed enterprise data centers or branch offices
across IP Wide Area Networks (WAN) where enterprise own router
devices are deployed as L2VPN or L3VPN Provider Edge (PE) routers. In
this case, efficient load balancing of the MPLS application traffic
across IP networks is very desirable.
1.1. Existing Technologies
With existing IP-based encapsulation methods for MPLS applications,
such as MPLS-in-IP and MPLS-in-Generic Routing Encapsulation (GRE)
[RFC4023] or even MPLS-in-Layer Two Tunneling Protocol - Version 3
(L2TPv3)[RFC4817], distinct customer traffic flows between a given PE
router pair would be encapsulated with the same IP-based tunnel
headers prior to traversing the core of the IP WAN. Since the
encapsulated traffic is neither TCP nor UDP traffic, for many
existing core routers which could only perform hash calculation on
fields in the IP headers of those tunnels (i.e., source IP address,
destination IP address), it would be hard to achieve a fine-grained
load balancing of these traffic flows across the network core due to
the lack of adequate entropy information.
[RFC5640] describes a method for improving the load balancing
efficiency in a network carrying Softwire Mesh service over L2TPv3
and GRE encapsulation. However, this method requires core routers to
be capable of performing hash calculation on the "load-balancing"
field contained in the tunnel encapsulation headers (i.e., the
Session ID field in the L2TPv3 header or the Key field in the GRE
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header), which means a non-trivial change to the date plane of many
existing core routers.
1.2. Motivations for MPLS-in-UDP Encapsulation
On basis of the fact that most existing core routers (i.e., P routers
in the context of MPLS-based L2VPN or L3VPN) are already capable of
balancing IP traffic flows over the IP networks based on the hash of
the five-tuple of UDP packets, it would be advantageous to use MPLS-
in-UDP encapsulation instead of MPLS-in-GRE or MPLS-in-L2TPv3 in the
environments where the load balancing of MPLS application traffic
across IP networks is much desired but the load balancing mechanisms
defined in [RFC5640] have not yet been widely supported by most
existing core routers. In this way, the default load balancing
capability of most existing core routers as mentioned above can be
utilized directly without requiring any change to them.
2. Terminology
This memo makes use of the terms defined in [RFC4364] and [RFC4664].
3. Encapsulation in UDP
MPLS-in-UDP encapsulation format is shown as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = Entropy | Dest Port = MPLS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ MPLS Label Stack ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Message Body ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Port of UDP
This field contains an entropy value that is generated by
the ingress PE router. For example, the entropy value can
be generated by performing hash calculation on certain
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fields in the customer packets (e.g., the five tuple of
UDP/TCP packets).
Destination Port of UDP
This field is set to a value (TBD) indicating that the
UDP tunnel payload is a MPLS packet. As for whether the
top label in the MPLS label stack is downstream-assigned
or upstream-assigned, it SHOULD be determined based on
the tunnel destination IP address. That is to say, if the
destination IP address is a multicast address, the top
label SHOULD be upstream-assigned, otherwise if the
destination IP address is a unicast address, it SHOULD be
downstream-assigned.
UDP Length
The usage of this field is in accordance with the current
UDP specification.
UDP Checksum
The usage of this field is in accordance with the current
UDP specification. To simplify the operation on egress PE
routers, this field is RECOMMENDED to be set to zero in
IPv4 UDP encapsulation case, and even in IPv6 UDP
encapsulation case if appropriate[RFC6935][RFC6936].
MPLS Label Stack
This field contains an MPLS Label Stack as defined in
[RFC3032].
Message Body
This field contains one MPLS message body.
4. Processing Procedures
This MPLS-in-UDP encapsulation causes MPLS packets to be forwarded
through "UDP tunnels". When performing MPLS-in-UDP encapsulation by
an ingress PE router, the entropy value would be generated by the
ingress PE router and then be filled in the Source Port field of the
UDP header. As such, P routers, upon receiving these UDP encapsulated
packets, could balance these packets based on the hash of the five-
tuple of UDP packets.
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Upon receiving these UDP encapsulated packets, egress PE routers
would decapsulate them by removing the UDP headers and then process
them accordingly.
As for other common processing procedures associated with tunneling
encapsulation technologies including but not limited to Maximum
Transmission Unit (MTU) and preventing fragmentation and reassembly,
Time to Live (TTL) and differentiated services, the corresponding
procedures defined in [RFC4023] which are applicable for MPLS-in-IP
and MPLS-in-GRE encapsulation formats SHOULD be followed.
5. Applicability
Besides the MPLS-based L3VPN [RFC4364] and L2VPN [RFC4761, RFC4762]
applications, MPLS-in-UDP encapsulation could apply to other MPLS
applications including but not limited to 6PE [RFC4798] and PWE3
services.
6. Security Considerations
Just like MPLS-in-GRE and MPLS-in-IP encapsulation formats, the MPLS-
in-UDP encapsulation format defined in this document by itself cannot
ensure the integrity and privacy of data packets being transported
through the MPLS-in-UDP tunnels and cannot enable the tunnel
decapsulators to authenticate the tunnel encapsulator. In the case
where any of the above security issues is concerned, the MPLS-in-UDP
tunnels SHOULD be secured with IPsec in transport mode. In this way,
the UDP header would not be visible to P routers anymore. As a result,
the meaning of adopting MPLS-in-UDP encapsulation format as an
alternative to MPLS-in-GRE and MPLS-in-IP encapsulation formats is
lost. Hence, MPLS-in-UDP encapsulation format SHOULD be used only in
the scenarios where all the security issues as mentioned above are
not significant concerns. For example, in a data center environment,
the whole network including P routers and PE routers are under the
control of a single administrative entity and therefore there is no
need to worry about the above security issues.
7. IANA Considerations
One UDP destination port number indicating MPLS needs to be allocated
by IANA.
8. Acknowledgements
Thanks to Shane Amante, Dino Farinacci, Keshava A K, Ivan Pepelnjak,
Eric Rosen, Andrew G. Malis, Kireeti Kompella, Marshall Eubanks,
George Swallow, Loa Andersson, Ross Callon, Vivek Kumar, Weiguo Hao,
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Zhenxiao Liu and Xing Tong for their valuable comments and
suggestions on this document. Thanks to Daniel King, Gregory Mirsky
and Eric Osborne for their valuable reviews on this document.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[RFC4364] Rosen, E and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4664] Andersson, L. and Rosen, E. (Editors),"Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664, Sept 2006.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS
in IP or GRE", RFC4023, March 2005.
[RFC4817] M. Townsley, C. Pignataro, S. Wainner, T. Seely and J.
Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3, March 2007.
[RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
Balancing for Mesh Softwires", RFC 5640, August 2009.
[RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS
Multicast Encapsulations", RFC 5332, August 2008.
[RFC4798] J Declerq et al., "Connecting IPv6 Islands over IPv4 MPLS
using IPv6 Provider Edge Routers (6PE)", RFC4798, February
2007.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
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[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "UDP
Checksums for Tunneled Packets", RFC6935,
Feburary 2013.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the use of IPv6 UDP Datagrams with Zero Checksums",
RFC6936, Feburary 2013.
[IP-in-UDP] Xu, etc, "Encapsulating IP in UDP", draft-xu-softwire-ip-
in-udp-01 (work in progress), February 2013.
Authors' Addresses
Xiaohu Xu
Huawei Technologies
Beijing, China
Phone: +86-10-60610041
Email: xuxiaohu@huawei.com
Nischal Sheth
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
Email: nsheth@juniper.net
Lucy Yong
Huawei USA
5340 Legacy Dr.
Plano TX75025
Phone: 469-277-5837
Email: Lucy.yong@huawei.com
Carlos Pignataro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
USA
EMail: cpignata@cisco.com
Yongbing Fan
China Telecom
Guangzhou, China.
Phone: +86 20 38639121
Email: fanyb@gsta.com
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Zhenbin Li
Huawei Technologies,
Beijing, China
Phone: +86-10-60613676
Email: lizhenbin@huawei.com
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