Internet DRAFT - draft-xu-softwire-ip-in-udp
draft-xu-softwire-ip-in-udp
Network Working Group X. Xu
Internet-Draft Huawei Technologies
Intended status: Standards Track R. Asati
Expires: June 6, 2015 Cisco Systems
L. Yong
Huawei USA
Y. Lee
Comcast
Y. Fan
China Telecom
I. Beijnum
Institute IMDEA Networks
December 3, 2014
Encapsulating IP in UDP
draft-xu-softwire-ip-in-udp-03
Abstract
Existing Softwire encapsulation technologies are not adequate for
efficient load balancing of Softwire service traffic across IP
networks. This document specifies additional Softwire encapsulation
technology, referred to as IP-in-User Datagram Protocol (UDP), which
can facilitate the load balancing of Softwire service traffic across
IP networks.
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
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This Internet-Draft will expire on June 6, 2015.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Encapsulation in UDP . . . . . . . . . . . . . . . . . . . . 3
4. Processing Procedures . . . . . . . . . . . . . . . . . . . . 5
5. Congestion Considerations . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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. [RFC5640] describes a
method for improving the load balancing efficiency in a network
carrying Softwire Mesh service [RFC5565] over Layer Two Tunneling
Protocol - Version 3 (L2TPv3) [RFC3931] and Generic Routing
Encapsulation (GRE) [RFC2784] encapsulations. However, this method
requires core routers to perform hash calculation on the "load-
balancing" field contained in tunnel encapsulation headers (i.e., the
Session ID field in L2TPv3 headers or the Key field in GRE headers),
which is not widely supported by existing core routers.
Most existing routers in IP networks are already capable of
distributing IP traffic "microflows" [RFC2474] over ECMP paths and/or
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LAG based on the hash of the five-tuple of User Datagram Protocol
(UDP) [RFC0768] and Transmission Control Protocol (TCP) packets
(i.e., source IP address, destination IP address, source port,
destination port, and protocol). By encapsulating the Softwire
service traffic into an UDP tunnel and using the source port of the
UDP header as an entropy field, the existing load-balancing
capability as mentioned above can be leveraged to provide fine-
grained load-balancing of Softwire service traffic traffic over IP
networks. This is similar to why LISP [RFC6830] uses UDP
encapsulation. Therefore, this specification defines an IP-in-UDP
encapsulation method for Software service (including both mesh and
hub-spoke modes).
IPv6 flow label has been proposed as an entropy field for load
balancing in IPv6 network environment [RFC6438]. However, as stated
in [RFC6936], the end-to-end use of flow labels for load balancing is
a long-term solution and therefore the use of load balancing using
the transport header fields would continue until any widespread
deployment is finally achieved. As such, IP-in-UDP encapsulation
would still have a practical application value in the IPv6 networks
during this transition timeframe.
Similarly, the IP-in-UDP encapsulation format defined in this
document by itself cannot ensure the integrity and privacy of data
packets being transported through the IP-in-UDP tunnels and cannot
enable the tunnel decapsulators to authenticate the tunnel
encapsulator. Therefore, in the case where any of the above security
issues is concerned, the IP-in-UDP SHOULD be secured with IPsec
[RFC4301] or DTLS [RFC6347]. For more details, please see Section 6
of Security Considerations.
1.1. Conventions
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].
2. Terminology
This memo makes use of the terms defined in [RFC5565].
3. Encapsulation in UDP
IP-in-UDP encapsulation format is shown as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = Entropy | Dest Port = TBD1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ IP Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Port of UDP
This field contains a 16-bit entropy value that is generated by
the encapsulator to uniquely identify a flow. What constitutes
a flow is locally determined by the encapsulator and therefore
is outside the scope of this document. What algorithm is
actually used by the encapsulator to generate an entropy value
is outside the scope of this document.
In case the tunnel does not need entropy, this field of all
packets belonging to a given flow SHOULD be set to a randomly
selected constant value so as to avoid packet reordering.
To ensure that the source port number is always in the range
49152 to 65535 (Note that those ports less than 49152 are
reserved by IANA to identify specific applications/protocols)
which may be required in some cases, instead of calculating a
16-bit hash, the encapsulator SHOULD calculate a 14-bit hash
and use those 14 bits as the least significant bits of the
source port field while the most significant two bits SHOULD be
set to binary 11. That still conveys 14 bits of entropy
information which would be enough as well in practice.
Destination Port of UDP
This field is set to a value (TBD1) allocated by IANA to
indicate that the UDP tunnel payload is an IP packet. As for
whether the encapsulated IP packet is IPv4 or IPv6, it would be
determined according to the Version field in the IP header of
the encapsulated IP packet.
UDP Length
The usage of this field is in accordance with the current UDP
specification [RFC0768].
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UDP Checksum
For IPv4 UDP encapsulation, this field is RECOMMENDED to be set
to zero because the IPv4 header includes a checksum and use of
the UDP checksum is optional with IPv4. For IPv6 UDP
encapsulation, the IPv6 header does not include a checksum, so
this field MUST contain a UDP checksum that MUST be used as
specified in [RFC0768] and [RFC2460] unless one of the
exceptions that allows use of UDP zero-checksum mode (as
specified in [RFC6935]) applies.
IP Packet
This field contains one IP packet.
4. Processing Procedures
This IP-in-UDP encapsulation causes E-IP[RFC5565] packets to be
forwarded across an I-IP [RFC5565] transit core via "UDP tunnels".
While performing IP-in-UDP encapsulation, an ingress AFBR (e.g. PE
router) would generate an entropy value and encode it in the Source
Port field of the UDP header. The Destination Port field is set to a
value (TBD1) allocated by IANA to indicate that the UDP tunnel
payload is an IP packet. Transit routers, upon receiving these UDP
encapsulated IP packets, could balance these packets based on the
hash of the five-tuple of UDP packets. Egress AFBRs receiving these
UDP encapsulated IP packets MUST decapsulate these packets by
removing the UDP header and then forward them accordingly (assuming
that the Destination Port was set to the reserved value pertaining to
IP).
Similar to all other Softwire tunneling technologies, IP-in-UDP
encapsualtion introduces overheads and reduces the effective Maximum
Transmision Unit (MTU) size. IP-in-UDP encapsulation may also impact
Time-to-Live (TTL) or Hop Count (HC) and Differentiated Services
(DSCP). Hence, IP-in-UDP MUST follow the corresponding procedures
defined in [RFC2003]. If an ingress AFBR performs fragmentation on
an E-IP packet before encapsulating, it MUST use the same source UDP
port for all fragmented packets so as to ensures these fragmented
packets are always forwarded on the same path.
5. Congestion Considerations
Section 3.1.3 of [RFC5405] discussed the congestion implications of
UDP tunnels. As discussed in [RFC5405], because other flows can
share the path with one or more UDP tunnels, congestion control
[RFC2914] needs to be considered. As specified in [RFC5405]:
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"IP-based traffic is generally assumed to be congestion-
controlled, i.e., it is assumed that the transport protocols
generating IP-based traffic at the sender already employ
mechanisms that are sufficient to address congestion on the path.
Consequently, a tunnel carrying IP-based traffic should already
interact appropriately with other traffic sharing the path, and
specific congestion control mechanisms for the tunnel are not
necessary".
Since IP-in-UDP is only used to carry IP traffic which is generally
assumed to be congestion controlled, it generally does not need
additional congestion control mechanisms.
6. Security Considerations
The security problems faced with the IP-in-UDP tunnel are exactly the
same as those faced with IP-in-IP [RFC2003] and IP-in-GRE tunnels
[RFC2784]. In other words, the IP-in-UDP tunnel as defined in this
document by itself cannot ensure the integrity and privacy of data
packets being transported through the IP-in-UDP tunnel and cannot
enable the tunnel decapsulator to authenticate the tunnel
encapsulator. In the case where any of the above security issues is
concerned, the IP-in-UDP tunnel SHOULD be secured with IPsec or DTLS.
IPsec was designed as a network security mechanism and therefore it
resides at the network layer. As such, if the tunnel is secured with
IPsec, the UDP header would not be visible to intermediate routers
anymore in either IPsec tunnel or transport mode. As a result, the
meaning of adopting the IP-in-UDP tunnel as an alternative to the IP-
in-GRE or IP-in-IP tunnel is lost. By comparison, DTLS is better
suited for application security and can better preserve network and
transport layer protocol information. Specifically, if DTLS is used,
the destination port of the UDP header will be filled with a value
(TBD2) indicating IP with DTLS and the source port can still be used
as an entropy field for load-sharing purposes.
If the tunnel is not secured with IPsec or DTLS, some other method
should be used to ensure that packets are decapsulated and forwarded
by the tunnel tail only if those packets were encapsulated by the
tunnel head. If the tunnel lies entirely within a single
administrative domain, address filtering at the boundaries can be
used to ensure that no packet with the IP source address of a tunnel
endpoint or with the IP destination address of a tunnel endpoint can
enter the domain from outside. However, when the tunnel head and the
tunnel tail are not in the same administrative domain, this may
become difficult, and filtering based on the destination address can
even become impossible if the packets must traverse the public
Internet. Sometimes only source address filtering (but not
destination address filtering) is done at the boundaries of an
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administrative domain. If this is the case, the filtering does not
provide effective protection at all unless the decapsulator of an IP-
in-UDP validates the IP source address of the packet.
7. IANA Considerations
One UDP destination port number indicating IP needs to be allocated
by IANA:
Service Name: IP-in-UDP
Transport Protocol(s): UDP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>.
Description: Encapsulate IP packets in UDP tunnels.
Reference: This document.
Port Number: TBD1 -- To be assigned by IANA.
One UDP destination port number indicating IP with DTLS needs to be
allocated by IANA:
Service Name: IP-in-UDP-with-DTLS
Transport Protocol(s): UDP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>.
Description: Encapsulate IP packets in UDP tunnels with DTLS.
Reference: This document.
Port Number: TBD2 -- To be assigned by IANA.
8. Acknowledgements
Thanks to Vivek Kumar, Carlos Pignataro and Mark Townsley for their
valuable comments on the initial idea of this document. Thanks to
Andrew G. Malis for his valuable comments on this document.
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9. References
9.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, November
2008.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[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.
9.2. Informative References
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, December
1998.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC
2914, September 2000.
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[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC5565] Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
Framework", RFC 5565, June 2009.
[RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
Balancing for Mesh Softwires", RFC 5640, August 2009.
[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.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, January
2013.
Authors' Addresses
Xiaohu Xu
Huawei Technologies
No.156 Beiqing Rd
Beijing 100095
CHINA
Phone: +86-10-60610041
Email: xuxiaohu@huawei.com
Rajiv Asati
Cisco Systems
7200 Kit Creek Road
Research Triangle Park,, NC 27709
USA
Email: rajiva@cisco.com
Lucy Yong
Huawei USA
5340 Legacy Dr
Plano, TX 75025
USA
Email: Lucy.yong@huawei.com
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Yiu Lee
Comcast
One Comcast Center
Philadelphia, PA
USA
Phone: Email: Yiu_Lee@Cable.Comcast.com
Email: cpignata@cisco.com
Yongbing Fan
China Telecom
Guangzhou
CHINA
Email: fanyb@gsta.com
Iljitsch van Beijnum
Institute IMDEA Networks
Avda. del Mar Mediterraneo, 22
Leganes,, Madrid 28918
Spain
Email: iljitsch@muada.com
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