Internet DRAFT - draft-yong-tsvwg-gre-in-udp-encap
draft-yong-tsvwg-gre-in-udp-encap
Network Working Group E. Crabbe, Ed.
Internet-Draft Google
Intended status: Standards Track L. Yong, Ed.
Expires: April 24, 2014 Huawei USA
X. Xu, Ed.
Huawei Technologies
October 21, 2013
Generic UDP Encapsulation for IP Tunneling
draft-yong-tsvwg-gre-in-udp-encap-02
Abstract
This document describes a method of encapsulating arbitrary protocols
within GRE and UDP headers. In this encapsulation, the source UDP
port may be used as an entropy field for purposes of loadbalancing
while the payload protocol may be identified by the GRE Protocol
Type.
Requirements Language
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 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 24, 2014.
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Copyright Notice
Copyright (c) 2013 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Encapsulation Considerations . . . . . . . . . . . . . . . . 6
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7.1. Vulnerability . . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Load balancing, or more specifically, statistical multiplexing of
traffic using Equal Cost Multi-Path (ECMP) and/or Link Aggregation
Groups (LAGs) in IP networks is a widely used technique for creating
higher capacity networks out of lower capacity links. Most existing
routers in IP networks are already capable of distributing IP traffic
flows over ECMP paths and/or LAGs on the basis of a hash function
performed on flow invariant fields in IP packet headers and their
payload protocol headers. Specifically, when the IP payload is a
User Datagram Protocol (UDP)[RFC0768] or Transmission Control
Protocol (TCP) packet, router hash functions frequently operate on
the five-tuple of the source IP address, the destination IP address,
the source port, the destination port, and the protocol/next-header
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Several tunneling techniques are in common use in IP networks, such
as Generic Routing Encapsulation (GRE) [RFC2784], MPLS [RFC4023] and
L2TPv3 [RFC3931]. GRE is an increasingly popular encapsulation
choice, especially in environments where MPLS is unavailable or
unnecessary. Unfortunately, use of common GRE endpoints may reduce
the entropy available for use in load balancing, especially in
environments where the GRE Key field [RFC2890] is not readilly
available for use as entropy in forwarding decisions.
This document defines a generic GRE-in-UDP encapsulation for
tunneling arbitrary network protocol payloads across an IP network
environment where ECMP or LAGs are used. The GRE header provides
payload protocol de-multiplexing by way of it's protocol type field
[RFC2784] while the UDP header provides additional entropy by way of
it's source port.
This encapsulation method requires no changes to the transit IP
network. Hash functions in most existing IP routers may utilize and
benefit from the use of a GRE-in-UDP tunnel without needing any
change or upgrade to to their ECMP implementations. The
encapsulation mechanism is applicable to a variety of IP networks
including Data Center and wide area networks.
2. Terminology
The terms defined in [RFC0768] are used in this document.
3. Procedures
When a tunnel ingress device conforming to this document receives a
packet, the ingress MUST encapsulate the packet in UDP and GRE
headers and set the destination port of the UDP header to [TBD]
Section 6. he ingress device must also insert the payload protocol
type in the GRE Protocol Type field. The ingress device SHOULD set
the UDP source port based on flow invariant fields from the payload
header, otherwise it should be set to a randomly selected constant
value, e.g. zero, to avoid packet flow reordering. How a tunnel
ingress generates entropy from the payload is outside the scope of
this document. The tunnel ingress MUST encode its own IP address as
the source IP address and the egress tunnel endpoint IP address. The
TTL field in the IP header must be set to a value appropriate for
delivery of the encapsulated packet to the tunnel egress endpoint.
When the tunnel egress receives a packet, it must remove the outer
UDP and GRE headers. Section 5 describes the error handling when
this entity is not instantiated at the tunnel egress.
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To simplify packet processing at the tunnel egress, packets destined
to this assigned UDP destination port [TBD] SHOULD have their UDP
checksum and Sequence flags set to zero because the egress tunnel
only needs to identify this protocol. Although IPv6 [RFC2460]
restricts the processing a packet with the UDP checksum of zero,
[RFC6935] and [RFC6936] relax this constraint to allow the zero UDP
checksum.
The tunnel ingress may set the GRE Key Present, Sequence Number
Present, and Checksum Present bits and asscociated fields in the GRE
header defined by [RFC2784] and [RFC2890].
In addition IPv6 nodes MUST conform to the following:
1. the IPv6 tunnel ingress and egress SHOULD follow the node
requirements specified in Section 4 of [RFC6936] and the usage
requirements specified in Section 5 of [RFC6936]
2. IPv6 transit nodes SHOULD follow the requirements 9, 10, 11
specified in Section 5 of [RFC6936].
The format of the GRE-in-UDP encapsulation for both IPv4 and IPv6
outer headersis shown in the followingfigures:
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
IPv4 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live |Protcol=17[UDP]| Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
UDP Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = XXXX | Dest Port = TBD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
GRE Header:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum (optional) | Reserved1 (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: UDP+GRE IPv4 headers
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
IPv6 Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | NxtHdr=17[UDP]| Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Outer Source IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Outer Destination IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
UDP Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = XXXX | Dest Port = TBD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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GRE Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|C| |K|S| Reserved0 | Ver | Protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum (optional) | Reserved1 (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: UDP+GRE IPv6 headers
The total overhead increase for a UDP+GRE tunnel without use of
optional GRE fields, representing the lowest total overhead increase,
is 32 bytes in the case of IPv4 and 52 bytes in the case of IPv6.
The total overhead increase for a UDP+GRE tunnel with use of GRE Key,
Sequence and Checksum Fields, representing the highest total overhead
increase, is 44 bytes in the case of IPv4 and 64 bytes in the case of
IPv6.
4. Encapsulation Considerations
GRE-in-UDP encapsulation allows the tunneled traffic to be unicast,
broadcast, or multicast traffic. Entropy may be generated from the
header of tunneled unicast or broadcast/multicast packets at tunnel
ingress. The mapping mechanism between the tunneled multicast
traffic and the multicast capability in the IP network is transparent
and independent to the encapsulation and is outside the scope of this
document.
If tunnel ingress must perform fragmentation on a packet before
encapsulation, it MUST use the same source UDP port for all packet
fragments. This ensures that the transit routers will forward the
packet fragments on the same path. GRE-in-UDP encapsulation
introduces some overhead as mentioned in section 3, which reduces the
effective Maximum Transmission Unit (MTU) size. An operator should
factor in this addition overhead bytes when considering an MTU size
for the payload to reduce the likelihood of fragmentation.
To ensure the tunneled traffic gets the same treatment over the IP
network, prior to the encapsulation process, tunnel ingress should
process the payload to get the proper parameters to fill into the IP
header such as DiffServ [[RFC2983]]. Tunnel end points that support
ECN MUST use the method described in [RFC6040] for ECN marking
propagation. This process is outside of the scope of this document.
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Note that the IPv6 header [RFC2460] contains a flow label field that
may be used for load balancing in an IPv6 network [RFC6438]. Thus in
an IPv6 network, either GRE-in-UDP or flow labels may be used in
order to improve load balancing performance. Use of GRE-in-UDP
encapsulation provides a unified hardware implementation for load
balancing in an IP network independent of the IP version(s) in use.
5. Backward Compatibility
It is assumed that tunnel ingress routers must be upgraded in order
to support the encapsulations described in this document.
No change is required at transit routers to support forwarding of the
encapsulation described in this document.
If a router that is intended for use as a tunnel egress does not
support the GRE-in-UDP encapsulation described in this document, it
will not be listening on destination port [TBD]. In these cases, the
router will conform to normal UDP processing and respond to the
tunnel ingress with an ICMP message indicating "port unreachable"
according to [RFC0792]. Upon receiving this ICMP message, the tunnel
ingress MUST NOT continue to use GRE-in-UDP encapsulation toward this
tunnel egress without management intervention.
6. IANA Considerations
IANA is requested to make the following allocation: Service Name:
GRE-in-UDP Transport Protocol(s): UDP Assignee: IESG iesg@ietf.org
Contact: IETF Chair chair@ietf.org Description: GRE-in-UDP
Encapsulation Reference: [This.I-D] Port Number: TBD Service Code: N/
A Known Unauthorized Uses: N/A Assignment Notes: N/A
7. Security Considerations
7.1. Vulnerability
Neither UDP nor GRE encapsulation effects security for the payload
protocol. When using GRE-in-UDP, Network Security in a network is
similar to that of a network using GRE.
Use of ICMP for signaling of the GRE-in-UDP encapsulation capability
adds a security concern. Tunnel ingress devices may want to validate
the origin of ICMP Port Unreachable messages before taking action.
The mechanism for performing this validation is out of the scope of
this document.
In an instance where the UDP src port is not set based et the flow
invariant fields from the payload header, a random port SHOULD be
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selected in order to minimize the vulnerability to off-path attacks.
[RFC6056] How the src port randomization occurs is outside scope of
this document.
8. Acknowledgements
The Authors would like to thank Vivek Kumar, Ron Bonica, Joe Touch,
Ruediger Geib, Gorry Fairhurst, and David Black for their review and
valuable input on this draft.
9. Contributing Authors
The following people all contributed significantly to this document
and are listed below in alphabetical order:
John E. Drake
Juniper Networks
Email: jdrake@juniper.net
Adrian Farrel
Juniper Networks
Email: adrian@olddog.co.uk
Vishwas Manral
Hewlett-Packard Corp.
3000 Hanover St, Palo Alto.
Email: vishwas.manral@hp.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
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10. References
10.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
[RFC2983] Black, D., "Differentiated Services and Tunnels", RFC
2983, October 2000.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, November
2008.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, November 2010.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165, RFC
6335, August 2011.
[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
for Equal Cost Multipath Routing and Link Aggregation in
Tunnels", RFC 6438, November 2011.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", RFC 6935, April 2013.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, April 2013.
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10.2. Informative References
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
4023, March 2005.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884,
April 2007.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
Authors' Addresses
Edward Crabbe (editor)
Google
1600 Amphitheatre Parkway
Mountain View, CA 94102
US
Email: edward.crabbe@gmail.com
Lucy Yong (editor)
Huawei USA
5340 Legacy Drive
San Jose, TX 75025
US
Email: lucy.yong@huawei.com
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Xiaohu Xu (editor)
Huawei Technologies
Beijing
China
Email: xuxiaohu@huawei.com
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