tech-invite   World Map     

3GPP     Specs     Glossaries     Architecture     IMS     UICC       IETF     RFCs     Groups     SIP     ABNFs       Search

RFC 8085


UDP Usage Guidelines

Part 3 of 3, p. 40 to 55
Prev Section


prevText      Top      ToC       Page 40 
7.  Summary

   This section summarizes the key guidelines made in Sections 3 - 6 in
   a tabular format (Table 1) for easy referencing.

   | Recommendation                                          | Section |
   | MUST tolerate a wide range of Internet path conditions  | 3       |
   | SHOULD use a full-featured transport (e.g., TCP)        |         |
   |                                                         |         |
   | SHOULD control rate of transmission                     | 3.1     |
   | SHOULD perform congestion control over all traffic      |         |
   |                                                         |         |
   | for bulk transfers,                                     | 3.1.2   |
   | SHOULD consider implementing TFRC                       |         |
   | else, SHOULD in other ways use bandwidth similar to TCP |         |
   |                                                         |         |
   | for non-bulk transfers,                                 | 3.1.3   |
   | SHOULD measure RTT and transmit max. 1 datagram/RTT     | 3.1.1   |
   | else, SHOULD send at most 1 datagram every 3 seconds    |         |
   | SHOULD back-off retransmission timers following loss    |         |
   |                                                         |         |
   | SHOULD provide mechanisms to regulate the bursts of     | 3.1.6   |
   | transmission                                            |         |
   |                                                         |         |
   | MAY implement ECN; a specific set of application        | 3.1.7   |
   | mechanisms are REQUIRED if ECN is used.                 |         |
   |                                                         |         |
   | for DiffServ, SHOULD NOT rely on implementation of PHBs | 3.1.8   |
   |                                                         |         |
   | for QoS-enabled paths, MAY choose not to use CC         | 3.1.9   |
   |                                                         |         |
   | SHOULD NOT rely solely on QoS for their capacity        | 3.1.10  |
   | non-CC controlled flows SHOULD implement a transport    |         |
   | circuit breaker                                         |         |
   | MAY implement a circuit breaker for other applications  |         |
   |                                                         |         |
   | for tunnels carrying IP traffic,                        | 3.1.11  |
   | SHOULD NOT perform congestion control                   |         |
   | MUST correctly process the IP ECN field                 |         |
   |                                                         |         |

Top      Up      ToC       Page 41 
   | for non-IP tunnels or rate not determined by traffic,   |         |
   | SHOULD perform CC or use circuit breaker                | 3.1.11  |
   | SHOULD restrict types of traffic transported by the     |         |
   | tunnel                                                  |         |
   |                                                         |         |
   | SHOULD NOT send datagrams that exceed the PMTU, i.e.,   | 3.2     |
   | SHOULD discover PMTU or send datagrams < minimum PMTU;  |         |
   | Specific application mechanisms are REQUIRED if PLPMTUD |         |
   | is used.                                                |         |
   |                                                         |         |
   | SHOULD handle datagram loss, duplication, reordering    | 3.3     |
   | SHOULD be robust to delivery delays up to 2 minutes     |         |
   |                                                         |         |
   | SHOULD enable IPv4 UDP checksum                         | 3.4     |
   | SHOULD enable IPv6 UDP checksum; Specific application   | 3.4.1   |
   | mechanisms are REQUIRED if a zero IPv6 UDP checksum is  |         |
   | used.                                                   |         |
   |                                                         |         |
   | SHOULD provide protection from off-path attacks         | 5.1     |
   | else, MAY use UDP-Lite with suitable checksum coverage  | 3.4.2   |
   |                                                         |         |
   | SHOULD NOT always send middlebox keep-alive messages    | 3.5     |
   | MAY use keep-alives when needed (min. interval 15 sec)  |         |
   |                                                         |         |
   | Applications specified for use in limited use (or       | 3.6     |
   | controlled environments) SHOULD identify equivalent     |         |
   | mechanisms and describe their use case.                 |         |
   |                                                         |         |
   | Bulk-multicast apps SHOULD implement congestion control | 4.1.1   |
   |                                                         |         |
   | Low volume multicast apps SHOULD implement congestion   | 4.1.2   |
   | control                                                 |         |
   |                                                         |         |
   | Multicast apps SHOULD use a safe PMTU                   | 4.2     |
   |                                                         |         |
   | SHOULD avoid using multiple ports                       | 5.1.2   |
   | MUST check received IP source address                   |         |
   |                                                         |         |
   | SHOULD validate payload in ICMP messages                | 5.2     |
   |                                                         |         |
   | SHOULD use a randomized source port or equivalent       | 6       |
   | technique, and, for client/server applications, SHOULD  |         |
   | send responses from source address matching request     |         |
   | 5.1                                                     |         |
   | SHOULD use standard IETF security protocols when needed | 6       |

                    Table 1: Summary of Recommendations

Top      Up      ToC       Page 42 
8.  References

8.1.  Normative References

   [RFC768]   Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,

   [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,

   [RFC1122]  Braden, R., Ed., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122,
              DOI 10.17487/RFC1122, October 1989,

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
              1996, <>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <>.

   [RFC2914]  Floyd, S., "Congestion Control Principles", BCP 41,
              RFC 2914, DOI 10.17487/RFC2914, September 2000,

   [RFC3828]  Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed.,
              and G. Fairhurst, Ed., "The Lightweight User Datagram
              Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July
              2004, <>.

   [RFC4787]  Audet, F., Ed. and C. Jennings, "Network Address
              Translation (NAT) Behavioral Requirements for Unicast
              UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
              2007, <>.

Top      Up      ToC       Page 43 
   [RFC4821]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
              Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,

   [RFC5348]  Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP
              Friendly Rate Control (TFRC): Protocol Specification",
              RFC 5348, DOI 10.17487/RFC5348, September 2008,

   [RFC5405]  Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
              for Application Designers", BCP 145, RFC 5405,
              DOI 10.17487/RFC5405, November 2008,

   [RFC6040]  Briscoe, B., "Tunnelling of Explicit Congestion
              Notification", RFC 6040, DOI 10.17487/RFC6040, November
              2010, <>.

   [RFC6298]  Paxson, V., Allman, M., Chu, J., and M. Sargent,
              "Computing TCP's Retransmission Timer", RFC 6298,
              DOI 10.17487/RFC6298, June 2011,

   [RFC8084]  Fairhurst, G., "Network Transport Circuit Breakers",
              BCP 208, RFC 8084, DOI 10.17487/RFC8084, March 2017,

8.2.  Informative References

   [ALLMAN]   Allman, M. and E. Blanton, "Notes on burst mitigation for
              transport protocols", March 2005.

              Ford, B., "Application Design Guidelines for Traversal
              through Network Address Translators", Work in Progress,
              draft-ford-behave-app-05, March 2007.

   [ENCAP]    Nordmark, E., Ed., Tian, A., Gross, J., Hudson, J.,
              Kreeger, L., Garg, P., Thaler, P., and T. Herbert,
              "Encapsulation Considerations", Work in Progress,
              draft-ietf-rtgwg-dt-encap-02, October 2016.

   [FABER]    Faber, T., Touch, J., and W. Yue, "The TIME-WAIT State in
              TCP and Its Effect on Busy Servers", Proc. IEEE Infocom,
              March 1999.

Top      Up      ToC       Page 44 
              Touch, J. and W. Townsley, "IP Tunnels in the Internet
              Architecture", Work in Progress,
              draft-ietf-intarea-tunnels-03, July 2016.

   [POSIX]    IEEE Std. 1003.1-2001, , "Standard for Information
              Technology - Portable Operating System Interface (POSIX)",
              Open Group Technical Standard: Base Specifications Issue
              6, ISO/IEC 9945:2002, December 2001.

   [RFC919]   Mogul, J., "Broadcasting Internet Datagrams", STD 5,
              RFC 919, DOI 10.17487/RFC0919, October 1984,

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, DOI 10.17487/RFC1112, August 1989,

   [RFC1536]  Kumar, A., Postel, J., Neuman, C., Danzig, P., and S.
              Miller, "Common DNS Implementation Errors and Suggested
              Fixes", RFC 1536, DOI 10.17487/RFC1536, October 1993,

   [RFC1546]  Partridge, C., Mendez, T., and W. Milliken, "Host
              Anycasting Service", RFC 1546, DOI 10.17487/RFC1546,
              November 1993, <>.

   [RFC2309]  Braden, B., Clark, D., Crowcroft, J., Davie, B., Deering,
              S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G.,
              Partridge, C., Peterson, L., Ramakrishnan, K., Shenker,
              S., Wroclawski, J., and L. Zhang, "Recommendations on
              Queue Management and Congestion Avoidance in the
              Internet", RFC 2309, DOI 10.17487/RFC2309, April 1998,

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,

   [RFC2675]  Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms",
              RFC 2675, DOI 10.17487/RFC2675, August 1999,

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743,
              DOI 10.17487/RFC2743, January 2000,

Top      Up      ToC       Page 45 
   [RFC2887]  Handley, M., Floyd, S., Whetten, B., Kermode, R.,
              Vicisano, L., and M. Luby, "The Reliable Multicast Design
              Space for Bulk Data Transfer", RFC 2887,
              DOI 10.17487/RFC2887, August 2000,

   [RFC2983]  Black, D., "Differentiated Services and Tunnels",
              RFC 2983, DOI 10.17487/RFC2983, October 2000,

   [RFC3048]  Whetten, B., Vicisano, L., Kermode, R., Handley, M.,
              Floyd, S., and M. Luby, "Reliable Multicast Transport
              Building Blocks for One-to-Many Bulk-Data Transfer",
              RFC 3048, DOI 10.17487/RFC3048, January 2001,

   [RFC3124]  Balakrishnan, H. and S. Seshan, "The Congestion Manager",
              RFC 3124, DOI 10.17487/RFC3124, June 2001,

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, DOI 10.17487/RFC3168, September 2001,

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,

   [RFC3303]  Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and
              A. Rayhan, "Middlebox communication architecture and
              framework", RFC 3303, DOI 10.17487/RFC3303, August 2002,

   [RFC3493]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
              Stevens, "Basic Socket Interface Extensions for IPv6",
              RFC 3493, DOI 10.17487/RFC3493, February 2003,

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <>.

Top      Up      ToC       Page 46 
   [RFC3551]  Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
              Video Conferences with Minimal Control", STD 65, RFC 3551,
              DOI 10.17487/RFC3551, July 2003,

   [RFC3738]  Luby, M. and V. Goyal, "Wave and Equation Based Rate
              Control (WEBRC) Building Block", RFC 3738,
              DOI 10.17487/RFC3738, April 2004,

   [RFC3758]  Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
              Conrad, "Stream Control Transmission Protocol (SCTP)
              Partial Reliability Extension", RFC 3758,
              DOI 10.17487/RFC3758, May 2004,

   [RFC3819]  Karn, P., Ed., Bormann, C., Fairhurst, G., Grossman, D.,
              Ludwig, R., Mahdavi, J., Montenegro, G., Touch, J., and L.
              Wood, "Advice for Internet Subnetwork Designers", BCP 89,
              RFC 3819, DOI 10.17487/RFC3819, July 2004,

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <>.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340,
              DOI 10.17487/RFC4340, March 2006,

   [RFC4341]  Floyd, S. and E. Kohler, "Profile for Datagram Congestion
              Control Protocol (DCCP) Congestion Control ID 2: TCP-like
              Congestion Control", RFC 4341, DOI 10.17487/RFC4341, March
              2006, <>.

Top      Up      ToC       Page 47 
   [RFC4342]  Floyd, S., Kohler, E., and J. Padhye, "Profile for
              Datagram Congestion Control Protocol (DCCP) Congestion
              Control ID 3: TCP-Friendly Rate Control (TFRC)", RFC 4342,
              DOI 10.17487/RFC4342, March 2006,

   [RFC4380]  Huitema, C., "Teredo: Tunneling IPv6 over UDP through
              Network Address Translations (NATs)", RFC 4380,
              DOI 10.17487/RFC4380, February 2006,

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,

   [RFC4654]  Widmer, J. and M. Handley, "TCP-Friendly Multicast
              Congestion Control (TFMCC): Protocol Specification",
              RFC 4654, DOI 10.17487/RFC4654, August 2006,

   [RFC4880]  Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
              Thayer, "OpenPGP Message Format", RFC 4880,
              DOI 10.17487/RFC4880, November 2007,

   [RFC4890]  Davies, E. and J. Mohacsi, "Recommendations for Filtering
              ICMPv6 Messages in Firewalls", RFC 4890,
              DOI 10.17487/RFC4890, May 2007,

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,

   [RFC4963]  Heffner, J., Mathis, M., and B. Chandler, "IPv4 Reassembly
              Errors at High Data Rates", RFC 4963,
              DOI 10.17487/RFC4963, July 2007,

   [RFC4987]  Eddy, W., "TCP SYN Flooding Attacks and Common
              Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,

Top      Up      ToC       Page 48 
   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245,
              DOI 10.17487/RFC5245, April 2010,

   [RFC5622]  Floyd, S. and E. Kohler, "Profile for Datagram Congestion
              Control Protocol (DCCP) Congestion ID 4: TCP-Friendly Rate
              Control for Small Packets (TFRC-SP)", RFC 5622,
              DOI 10.17487/RFC5622, August 2009,

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,

   [RFC5681]  Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
              Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,

   [RFC5740]  Adamson, B., Bormann, C., Handley, M., and J. Macker,
              "NACK-Oriented Reliable Multicast (NORM) Transport
              Protocol", RFC 5740, DOI 10.17487/RFC5740, November 2009,

   [RFC5751]  Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
              Mail Extensions (S/MIME) Version 3.2 Message
              Specification", RFC 5751, DOI 10.17487/RFC5751, January
              2010, <>.

   [RFC5775]  Luby, M., Watson, M., and L. Vicisano, "Asynchronous
              Layered Coding (ALC) Protocol Instantiation", RFC 5775,
              DOI 10.17487/RFC5775, April 2010,

   [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
              Signalling Transport", RFC 5971, DOI 10.17487/RFC5971,
              October 2010, <>.

   [RFC5973]  Stiemerling, M., Tschofenig, H., Aoun, C., and E. Davies,
              "NAT/Firewall NSIS Signaling Layer Protocol (NSLP)",
              RFC 5973, DOI 10.17487/RFC5973, October 2010,

   [RFC6056]  Larsen, M. and F. Gont, "Recommendations for Transport-
              Protocol Port Randomization", BCP 156, RFC 6056,
              DOI 10.17487/RFC6056, January 2011,

Top      Up      ToC       Page 49 
   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              DOI 10.17487/RFC6092, January 2011,

   [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, DOI 10.17487/RFC6335, August 2011,

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <>.

   [RFC6396]  Blunk, L., Karir, M., and C. Labovitz, "Multi-Threaded
              Routing Toolkit (MRT) Routing Information Export Format",
              RFC 6396, DOI 10.17487/RFC6396, October 2011,

   [RFC6437]  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
              "IPv6 Flow Label Specification", RFC 6437,
              DOI 10.17487/RFC6437, November 2011,

   [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,

   [RFC6513]  Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
              BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
              2012, <>.

   [RFC6679]  Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
              and K. Carlberg, "Explicit Congestion Notification (ECN)
              for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
              2012, <>.

   [RFC6726]  Paila, T., Walsh, R., Luby, M., Roca, V., and R. Lehtonen,
              "FLUTE - File Delivery over Unidirectional Transport",
              RFC 6726, DOI 10.17487/RFC6726, November 2012,

Top      Up      ToC       Page 50 
   [RFC6773]  Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
              Datagram Congestion Control Protocol UDP Encapsulation for
              NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November
              2012, <>.

   [RFC6807]  Farinacci, D., Shepherd, G., Venaas, S., and Y. Cai,
              "Population Count Extensions to Protocol Independent
              Multicast (PIM)", RFC 6807, DOI 10.17487/RFC6807, December
              2012, <>.

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,

   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935,
              DOI 10.17487/RFC6935, April 2013,

   [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,

   [RFC6951]  Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
              Control Transmission Protocol (SCTP) Packets for End-Host
              to End-Host Communication", RFC 6951,
              DOI 10.17487/RFC6951, May 2013,

   [RFC7143]  Chadalapaka, M., Satran, J., Meth, K., and D. Black,
              "Internet Small Computer System Interface (iSCSI) Protocol
              (Consolidated)", RFC 7143, DOI 10.17487/RFC7143, April
              2014, <>.

   [RFC7201]  Westerlund, M. and C. Perkins, "Options for Securing RTP
              Sessions", RFC 7201, DOI 10.17487/RFC7201, April 2014,

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <>.

   [RFC7450]  Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450,
              DOI 10.17487/RFC7450, February 2015,

Top      Up      ToC       Page 51 
   [RFC7510]  Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
              "Encapsulating MPLS in UDP", RFC 7510,
              DOI 10.17487/RFC7510, April 2015,

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <>.

   [RFC7560]  Kuehlewind, M., Ed., Scheffenegger, R., and B. Briscoe,
              "Problem Statement and Requirements for Increased Accuracy
              in Explicit Congestion Notification (ECN) Feedback",
              RFC 7560, DOI 10.17487/RFC7560, August 2015,

   [RFC7567]  Baker, F., Ed. and G. Fairhurst, Ed., "IETF
              Recommendations Regarding Active Queue Management",
              BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015,

   [RFC7605]  Touch, J., "Recommendations on Using Assigned Transport
              Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
              August 2015, <>.

   [RFC7657]  Black, D., Ed. and P. Jones, "Differentiated Services
              (Diffserv) and Real-Time Communication", RFC 7657,
              DOI 10.17487/RFC7657, November 2015,

   [RFC7675]  Perumal, M., Wing, D., Ravindranath, R., Reddy, T., and M.
              Thomson, "Session Traversal Utilities for NAT (STUN) Usage
              for Consent Freshness", RFC 7675, DOI 10.17487/RFC7675,
              October 2015, <>.

   [RFC8083]  Perkins, C. and V. Singh, "Multimedia Congestion Control:
              Circuit Breakers for Unicast RTP Sessions", RFC 8083,
              DOI 10.17487/RFC8083, March 2017,

   [RFC8086]  Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
              in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
              March 2017, <>.

Top      Up      ToC       Page 52 
   [RFC8087]  Fairhurst, G. and M. Welzl, "The Benefits of Using
              Explicit Congestion Notification (ECN)", RFC 8087,
              DOI 10.17487/RFC8087, March 2017,

   [STEVENS]  Stevens, W., Fenner, B., and A. Rudoff, "UNIX Network
              Programming, The sockets Networking API", Addison-Wesley,

   [UPnP]     UPnP Forum, , "Internet Gateway Device (IGD) Standardized
              Device Control Protocol V 1.0", November 2001.

Top      Up      ToC       Page 53 
Appendix A.  Case Study of the Use of IPv6 UDP Zero-Checksum Mode

   This appendix provides a brief review of MPLS-in-UDP as an example of
   a UDP Tunnel Encapsulation that defines a UDP encapsulation.  The
   purpose of the appendix is to provide a concrete example of which
   mechanisms were required in order to safely use UDP zero-checksum
   mode for MPLS-in-UDP tunnels over IPv6.  By default, UDP requires a
   checksum for use with IPv6.  An option has been specified that
   permits a zero IPv6 UDP checksum when used in specific environments,
   specified in [RFC7510], and defines a set of operational constraints
   for use of this mode.  These are summarized below:

   A UDP tunnel or encapsulation using a zero-checksum mode with IPv6
   must only be deployed within a single network (with a single network
   operator) or networks of an adjacent set of cooperating network
   operators where traffic is managed to avoid congestion, rather than
   over the Internet where congestion control is required.  MPLS-in-UDP
   has been specified for networks under single administrative control
   (such as within a single operator's network) where it is known
   (perhaps through knowledge of equipment types and lower-layer checks)
   that packet corruption is exceptionally unlikely and where the
   operator is willing to take the risk of undetected packet corruption.

   The tunnel encapsulator SHOULD use different IPv6 addresses for each
   UDP tunnel that uses the UDP zero-checksum mode, regardless of the
   decapsulator, to strengthen the decapsulator's check of the IPv6
   source address (i.e., the same IPv6 source address SHOULD NOT be used
   with more than one IPv6 destination address, independent of whether
   that destination address is a unicast or multicast address).  Use of
   MPLS-in-UDP may be extended to networks within a set of closely
   cooperating network administrations (such as network operators who
   have agreed to work together to jointly provide specific services)

   The requirement for MPLS-in-UDP endpoints to check the source IPv6
   address in addition to the destination IPv6 address, plus the strong
   recommendation against reuse of source IPv6 addresses among MPLS-in-
   UDP tunnels collectively provide some mitigation for the absence of
   UDP checksum coverage of the IPv6 header.  In addition, the MPLS data
   plane only forwards packets with valid labels (i.e., labels that have
   been distributed by the tunnel egress Label Switched Router, LSR),
   providing some additional opportunity to detect MPLS-in-UDP packet
   misdelivery when the misdelivered packet contains a label that is not
   valid for forwarding at the receiving LSR.  The expected result for
   IPv6 UDP zero-checksum mode for MPLS-in-UDP is that corruption of the
   destination IPv6 address will usually cause packet discard, as
   offsetting corruptions to the source IPv6 and/or MPLS top label are

Top      Up      ToC       Page 54 
   Additional assurance is provided by the restrictions in the above
   exceptions that limit usage of IPv6 UDP zero-checksum mode to well-
   managed networks for which MPLS packet corruption has not been a
   problem in practice.  Hence, MPLS-in-UDP is suitable for transmission
   over lower layers in well-managed networks that are allowed by the
   exceptions stated above and the rate of corruption of the inner IP
   packet on such networks is not expected to increase by comparison to
   MPLS traffic that is not encapsulated in UDP.  For these reasons,
   MPLS-in-UDP does not provide an additional integrity check when UDP
   zero-checksum mode is used with IPv6, and this design is in
   accordance with requirements 2, 3, and 5 specified in Section 5 of

   The MPLS-in-UDP encapsulation does not provide a mechanism to safely
   fall back to using a checksum when a path change occurs that
   redirects a tunnel over a path that includes a middlebox that
   discards IPv6 datagrams with a zero UDP checksum.  In this case, the
   MPLS-in-UDP tunnel will be black-holed by that middlebox.
   Recommended changes to allow firewalls, NATs and other middleboxes to
   support use of an IPv6 zero UDP checksum are described in Section 5
   of [RFC6936].  MPLS does not accumulate incorrect state as a
   consequence of label-stack corruption.  A corrupt MPLS label results
   in either packet discard or forwarding (and forgetting) of the packet
   without accumulation of MPLS protocol state.  Active monitoring of
   MPLS-in-UDP traffic for errors is REQUIRED because the occurrence of
   errors will result in some accumulation of error information outside
   the MPLS protocol for operational and management purposes.  This
   design is in accordance with requirement 4 specified in Section 5 of
   [RFC6936].  In addition, IPv6 traffic with a zero UDP checksum MUST
   be actively monitored for errors by the network operator.

   Operators SHOULD also deploy packet filters to prevent IPv6 packets
   with a zero UDP checksum from escaping from the network due to
   misconfiguration or packet errors.  In addition, IPv6 traffic with a
   zero UDP checksum MUST be actively monitored for errors by the
   network operator.

Top      Up      ToC       Page 55 

   The middlebox traversal guidelines in Section 3.5 incorporate ideas
   from Section 5 of [BEHAVE-APP] by Bryan Ford, Pyda Srisuresh, and Dan
   Kegel.  The protocol timer guidelines in Section 3.1.1 were largely
   contributed by Mark Allman.

   G.  Fairhurst received funding from the European Union's Horizon 2020
   research and innovation program 2014-2018 under grant agreement No.
   644334 (NEAT).  Lars Eggert has received funding from the European
   Union's Horizon 2020 research and innovation program 2014-2018 under
   grant agreement No. 644866 (SSICLOPS).  This document reflects only
   the authors' views and the European Commission is not responsible for
   any use that may be made of the information it contains.

Authors' Addresses

   Lars Eggert
   Sonnenallee 1
   Kirchheim  85551

   Phone: +49 151 120 55791

   Godred Fairhurst
   University of Aberdeen
   Department of Engineering
   Fraser Noble Building
   Aberdeen  AB24 3UE


   Greg Shepherd
   Cisco Systems
   Tasman Drive
   San Jose
   United States of America