Internet DRAFT - draft-xu-intarea-ip-in-udp
draft-xu-intarea-ip-in-udp
INTAREA Working Group X. Xu
Internet-Draft China Mobile
Intended status: Standards Track H. Assarpour
Expires: 15 March 2024 Broadcom
S. Ma
Mellanox
D. Bernier
Canada Bell
D. Dukes
Cisco
S. Hegde
Juniper
Y. Lee
Comcast
Y. Fan
China Telecom
12 September 2023
Encapsulating IP in UDP
draft-xu-intarea-ip-in-udp-12
Abstract
Existing IP-in-IP encapsulation technologies are not adequate for
efficient load balancing of IP-in-IP traffic across IP networks.
This document specifies additional IP-in-IP encapsulation technology,
referred to as IP-in-UDP (User Datagram Protocol), which can
facilitate the load balancing of IP-in-IP traffic across IP networks.
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 RFC 2119 [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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 15 March 2024.
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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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Encapsulation in UDP . . . . . . . . . . . . . . . . . . . . 4
4. Processing Procedures . . . . . . . . . . . . . . . . . . . . 5
5. Congestion Considerations . . . . . . . . . . . . . . . . . . 6
6. Applicability Statements . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Security Considerations . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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 including Wide Area Networks (WAN) and
Data Center Networks (DCN) is widely used. There are increasing
applications of the IP-in-IP encapsulation on the WAN and DCN
environments, such as Global Accelerator (GA) on public cloud
providers' WAN and high-performance DCNs. [RFC5640] describes a
method for improving the load balancing efficiency of IP-in-IP
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traffic over Layer Two Tunneling Protocol - Version 3 (L2TPv3)
[RFC3931] and Generic Routing Encapsulation (GRE) [RFC2784]
encapsulations. However, this method requires core routers or
switches 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 and data center switches.
Most existing routers and data center switches are already capable of
distributing IP traffic "microflows" [RFC2474] over ECMP paths and/or
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 IP 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 IP-
in-IP traffic over IP networks. This is similar to why LISP
[RFC6830] , MPLS-in-UDP [RFC7510] and VXLAN [RFC7348] use UDP
encapsulation. Therefore, this specification defines an IP-in-UDP
encapsulation method which is an alternative encapsulation used in
[RFC5565] in addition to L2TPv3 and GRE.
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. Of course, it RECOMMENDED that the
IPv6 flow label is filled with an entropy value as well. In this
way, core routers or switches could perform load-balancing of IP-in-
IP traffic using either the approach as described in [RFC6438] or the
UDP five tuple accordingly.
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 DTLS
[RFC6347]. For more details, please see Section 9 of Security
Considerations.
2. Terminology
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3. Encapsulation in UDP
IP-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 = TBD1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ IP Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IP-in-UDP Encapsulation Format
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.
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 entropy, the encapsulator SHOULD calculate a 14-bit
entropy 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:
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The usage of this field is in accordance with the current UDP
specification [RFC0768].
UDP Checksum:
For IPv4 UDP encapsulation, this field is RECOMMENDED to be set
to zero for performance or implementation reasons 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 the original packets to be
forwarded across a transit IP network via "UDP tunnels". While
performing IP-in-UDP encapsulation, tunnel encapsulators 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 or switches, upon receiving these UDP
encapsulated packets, could balance these packets based on the hash
of the five-tuple of UDP packets. Tunnel decapsulators receiving
these UDP encapsulated 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 IP-in-IP tunneling technologies, IP-in-UDP
encapsulation introduces overheads and reduces the effective Maximum
Transmission 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].
Tunnel encapsulators MUST NOT fragment UDP encapsulated IP packets,
and when the outer IP header is IPv4, tunnel encapsulators MUST set
the DF bit in the outer IPv4 header. It is strongly RECOMMENDED that
the transit IP network be configured to carry an MTU at least large
enough to accommodate the added encapsulation headers. Meanwhile, it
is strongly RECOMMENDED that Path MTU Discovery [RFC1191] [RFC1981]
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or Packetization Layer Path MTU Discovery (PLPMTUD) [RFC4821] is used
to prevent or minimize fragmentation. Once an tunnel encapsulator
needs to perform fragmentation on an original 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. Note that fragmentation on the
original packets is possible only when the packets are IPv4 packets
and the DF bit is not set.
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]:
"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 by the transport layer, it
generally does not need additional congestion control mechanisms.
Furthermore, as it is explicitly stated in the Application Statements
(Section 6), this IP-in-UDP encapsulation method MUST only be used
within networks that are well-managed, therefore, congestion control
mechanism is not needed.
6. Applicability Statements
This IP-in-UDP encapsulation technology MUST only be used within
networks which are well-managed by a service provider and MUST NOT be
used within the Internet. In the well-managed network, traffic is
well-managed to avoid congestion and fragmentation are not needed.
7. 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, Joe Touch and Brian E Carpenter for their valuable
comments on this document.
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8. 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.
9. 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 or
switches 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.
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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
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.
10. References
10.1. Normative References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<https://www.rfc-editor.org/info/rfc768>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
1996, <https://www.rfc-editor.org/info/rfc1981>.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996,
<https://www.rfc-editor.org/info/rfc2003>.
[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>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
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[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<https://www.rfc-editor.org/info/rfc2784>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<https://www.rfc-editor.org/info/rfc4821>.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", RFC 5405,
DOI 10.17487/RFC5405, November 2008,
<https://www.rfc-editor.org/info/rfc5405>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", RFC 6935,
DOI 10.17487/RFC6935, April 2013,
<https://www.rfc-editor.org/info/rfc6935>.
[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<https://www.rfc-editor.org/info/rfc6936>.
10.2. 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,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.
[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed.,
"Layer Two Tunneling Protocol - Version 3 (L2TPv3)",
RFC 3931, DOI 10.17487/RFC3931, March 2005,
<https://www.rfc-editor.org/info/rfc3931>.
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[RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
Balancing for Mesh Softwires", RFC 5640,
DOI 10.17487/RFC5640, August 2009,
<https://www.rfc-editor.org/info/rfc5640>.
[RFC6438] Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
for Equal Cost Multipath Routing and Link Aggregation in
Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
<https://www.rfc-editor.org/info/rfc6438>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
"Encapsulating MPLS in UDP", RFC 7510,
DOI 10.17487/RFC7510, April 2015,
<https://www.rfc-editor.org/info/rfc7510>.
Authors' Addresses
Xiaohu Xu
China Mobile
Email: xuxiaohu_ietf@hotmail.com
Hamid Assarpour
Broadcom
Email: hamid.assarpour@broadcom.com
Shaowen Ma
Mellanox
Email: mashaowen@gmail.com
Daniel Bernier
Canada Bell
Email: daniel.bernier@bell.ca
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Darren Dukes
Cisco
Email: ddukes@cisco.com
Shraddha Hegde
Juniper
Email: shraddha@juniper.net
Yiu Lee
Comcast
Email: Yiu_Lee@Cable.Comcast.com
Yongbing Fan
China Telecom
Email: fanyb@gsta.com
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