--- 1/draft-ietf-taps-transports-00.txt 2014-12-18 06:14:53.089145415 -0800 +++ 2/draft-ietf-taps-transports-01.txt 2014-12-18 06:14:53.117146098 -0800 @@ -1,20 +1,21 @@ Network Working Group G. Fairhurst, Ed. Internet-Draft University of Aberdeen Intended status: Informational B. Trammell, Ed. -Expires: June 18, 2015 ETH Zurich - December 15, 2014 +Expires: June 22, 2015 M. Kuehlewind, Ed. + ETH Zurich + December 19, 2014 Services provided by IETF transport protocols and congestion control mechanisms - draft-ietf-taps-transports-00 + draft-ietf-taps-transports-01 Abstract This document describes services provided by existing IETF protocols and congestion control mechanisms. It is designed to help application and network stack programmers and to inform the work of the IETF TAPS Working Group. Status of This Memo @@ -24,21 +25,21 @@ 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 http://datatracker.ietf.org/drafts/current/. 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 June 18, 2015. + This Internet-Draft will expire on June 22, 2015. Copyright Notice Copyright (c) 2014 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -46,168 +47,495 @@ to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 1. Introduction Most Internet applications make use of the Transport Services provided by TCP (a reliable, in-order stream protocol) or UDP (an unreliable datagram protocol). We use the term "Transport Service" - to mean an end-to-end facility provided by the transport layer. That - service can only be provided correctly if information is supplied - from the application. The application may determine the information - to be supplied at design time, compile time, or run time and may - include guidance on whether an aspect of the service is required, a - preference by the application, or something in between. Examples of - Transport service facilities are reliable delivery, ordered delivery, - content privacy to in-path devices, integrity protection, and minimal - latency. - - Transport protocols such as SCTP, DCCP, MPTCP, UDP and UDP-Lite have - been defined at the transport layer. + to mean the end-to-end service provided to an application by the + transport layer. That service can only be provided correctly if + information about the intended usage is supplied from the + application. The application may determine this information at + design time, compile time, or run time, and may include guidance on + whether a feature is required, a preference by the application, or + something in between. Examples of features of Transport Services are + reliable delivery, ordered delivery, content privacy to in-path + devices, integrity protection, and minimal latency. - In addition, a transport service may be built on top of these - transport protocols, using a fraemwork such as WebSockets, or RTP. - Service built on top of UDP or UDP-Lite typically also need to - specify a congestion control mechanism, such as TFRC or the LEDBAT - congestion control mechanism. This extends the set of available - Transport Services beyond those provided to applications by TCP and - UDP. + The IETF has defined a wide variety of transport protocols beyond TCP + and UDP, including TCP, SCTP, DCCP, MP-TCP, and UDP-Lite. Transport + services may be provided directly by these transport protocols, or + layered on top of them using protocols such as WebSockets (which runs + over TCP) or RTP (over TCP or UDP). Services built on top of UDP or + UDP-Lite typically also need to specify additional mechanisms, + including a congestion control mechanism (such as a windowed + congestion control, TFRC or LEDBAT congestion control mechanism). + This extends the set of available Transport Services beyond those + provided to applications by TCP and UDP. - Transport services can aslo be differentiated by the services they - provide: for instance, SCTP offers a message-based service that does - not suffer head-of-line blocking when used with multiple stream, - because it can accept blocks of data out of order, UDP-Lite provides - partial integrity protection when used over link-layer services that - can support this, and LEDBAT can provide low-priority "scavenger" - communication. + Transport protocols can also be differentiated by the features of the + services they provide: for instance, SCTP offers a message-based + service that does not suffer head-of-line blocking when used with + multiple stream, because it can accept blocks of data out of order, + UDP-Lite provides partial integrity protection, and LEDBAT can + provide low-priority "scavenger" communication. 2. Terminology The following terms are defined throughout this document, and in subsequent documents produced by TAPS describing the composition and decomposition of transport services. - The terminology below is that as was presented at the TAPS WG meeting - in Honolulu. While the factoring of the terminology seems - uncontroversial, thre may be some entities which still require names + [Editor Note: The terminology below was presented at the TAPS WG + meeting in Honolulu. While the factoring of the terminology seems + uncontroversial, there may be some entities which still require names (e.g. information about the interface between the transport and lower layers which could lead to the availablity or unavailibility of - certain transport protocol features) + certain transport protocol features). Comments are welcome via the + TAPS mailing list.] - Transport Service Feature: a specific feature a transport service - provides to its clients end-to-end. Examples include + Transport Service Feature: a specific end-to-end feature that a + transport service provides to its clients. Examples include confidentiality, reliable delivery, ordered delivery, message- versus-stream orientation, etc. Transport Service: a set of transport service features, without an association to any given framing protocol, which provides a complete service to an application. Transport Protocol: an implementation that provides one or more different transport services using a specific framing and header format on the wire. Transport Protocol Component: an implementation of a transport - service feature within a protocol + service feature within a protocol. Transport Service Instance: an arrangement of transport protocols with a selected set of features and configuration parameters that implements a single transport service, e.g. a protocol stack (RTP - over UDP) + over UDP). Application: an entity that uses the transport layer for end-to-end - delivery data across the network. + delivery data across the network (this may also be an upper layer + protocol or tunnel encpasulation). -3. Transport Protocols +3. Existing Transport Protocols This section provides a list of known IETF transport protocol and transport protocol frameworks. + [Editor Note: Contributions to the sections in the list below are + welcome] + 3.1. Transport Control Protocol (TCP) - TCP [RFC0793] provides a bidirectional byte-oriented stream over a - connection- oriented protocol. The protocol and API use the byte- - stream model. + TCP is an IETF standards track transport protocol. [RFC0793] + introduces TCP as follows: "The Transmission Control Protocol (TCP) + is intended for use as a highly reliable host-to-host protocol + between hosts in packet-switched computer communication networks, and + in interconnected systems of such networks." Since its introduction, + TCP has become the default connection-oriented, stream-based + transport protocol in the Internet. It is widely implemented by + endpoints and widely used by common applications. - [EDITOR'S NOTE: Mirja Kuehlewind signed up as contributor for this - section.] +3.1.1. Protocol Description -3.1.1. Multipath TCP (MPTCP) + TCP is a connection-oriented protocol, providing a three way + handshake to allow a client and server to set up a connection, and + mechanisms for orderly completion and immediate teardown of a + connection. TCP is defined by a family of RFCs [RFC4614]. -3.2. Stream Control Transmission Protocol (SCTP) + TCP provides multiplexing to multiple sockets on each host using port + numbers. An active TCP session is identified by its four-tuple of + local and remote IP addresses and local port and remote port numbers. - SCTP [RFC4960] provides a bidirectional set of logical unicast - streams over one a connection-oriented protocol. The protocol and - API use messages, rather than a byte-stream. Each stream of messages - is independently managed, therefore retransmission does not hold back + TCP partitions a continuous stream of bytes into segments, sized to + fit in IP packets, constrained by the maximum size of lower layer + frame. PathMTU discovery is supported. Each byte in the stream is + identified by a sequence number. The sequence number is used to + order segments on receipt, to identify segments in acknowledgments, + and to detect unacknowledged segments for retransmission. This is + the basis of TCP's reliable, ordered delivery of data in a stream. + TCP Selective Acknowledgment [RFC2018] extends this mechanism by + making it possible to identify missing segments more precisely, + reducing spurious retransmission. + + Receiver flow control is provided by a sliding window: limiting the + amount of unacknowledged data that can be outstanding at a given + time. The window scale option [RFC7323] allows a receiver to use + windows greater than 64KB. + + All TCP senders provide Congestion Control: This uses a separate + window, where each time congestion is detected, this congestion + window is reduced. A receiver detects congestion using one of three + mechanisms: A retransmission timer, loss (interpreted as a congestion + signal), and Explicit Congestion Notification (ECN) [RFC3168] to + provide early signaling (see [I-D.ietf-aqm-ecn-benefits]) + + A TCP protocol instance can be extended [RFC4614] and tuned. Some + features are sender-side only, requiring no negotiation with the + receiver; some are receiver-side only, some are explicitly negotiated + during connection setup. + + By default, TCP segment partitioning uses Nagle's algorithm [RFC0896] + to buffer data at the sender into large segments, potentially + incurring sender-side buffering delay; this algorithm can be disabled + by the sender to transmit more immediately, e.g. to enable smoother + interactive sessions. + + A TCP service is unicast. + +3.1.2. Interface description + + A TCP API is defined in [REF], but there is currently no API + specified in the RFC series. + + In API implementations derived from the BSD Sockets API, TCP sockets + are created using the "SOCK_STREAM" socket type. + + The features used by a protocol instance may be set and tuned via + this API. + + (more on the API goes here) + +3.1.3. Transport Protocol Components + + The transport protocol components provided by TCP are: + + o unicast + + o connection-oriented setup with feature negotiation + + o port multiplexing + + o reliable delivery + + o ordered delivery + + o segmented, stream-oriented delivery in a single stream + + o congestion control + + (discussion of how to map this to features and TAPS: what does the + higher layer need to decide? what can the transport layer decide + based on global settings? what must the transport layer decide based + on network characteristics?) + +3.2. Multipath TCP (MP-TCP) + + [Editor Note: a few sentences describing Multipath TCP [RFC6824] go + here. Note that this adds transport-layer multihoming to the + components TCP provides] + +3.3. Stream Control Transmission Protocol (SCTP) + + SCTP [RFC4960] is an IETF standards track transport protocol that + provides a bidirectional s set of logical unicast meessage streams + over a connection-oriented protocol. The protocol and API use + messages, rather than a byte-stream. Each stream of messages is + independently managed, therefore retransmission does not hold back data sent using other logical streams. + The SCTP Partial Reliability Extension (SCTP-PR) is defined in + [RFC3758]. + [EDITOR'S NOTE: Michael Tuexen and Karen Nielsen signed up as contributors for these sections.] -3.2.1. Partial Reliability for SCTP (PR-SCTP) +3.3.1. Protocol Description - PR-SCTP [RFC3758] is a variant of SCTP that provides partial - reliability. + An SCTP service is unicast. -3.3. User Datagram Protocol (UDP) +3.3.2. Interface Description - The User Datagram Protocol (UDP) [RFC0768] provides a unidirectional + The SCTP API is described in the specifications published in the RFC + series. + +3.3.3. Transport Protocol Components + + The transport protocol components provided by SCTP are: + + o unicast + + o connection-oriented setup with feature negotiation + + o port multiplexing + + o reliable or partially reliable delivery + + o ordered delivery within a stream + + o support for multiple prioritised streams + + o message-oriented delivery + + o congestion control + + [EDITOR'S NOTE: Please update list.] + +3.4. User Datagram Protocol (UDP) + + The User Datagram Protocol (UDP) [RFC0768] [RFC2460] is an IETF + standards track transport protocol. It provides a uni-directional minimal message-passing transport that has no inherent congestion - control mechanisms. The service may be multicast and/or unicast. + control mechanisms or other transport functions. IETF guidance on + the use of UDP is provided in [RFC5405]. UDP is widely implemented + by endpoints and widely used by common applications. - [EDITOR'S NOTE: Kevin Fall signed up as contributor for this + [EDITOR'S NOTE: Kevin Fall signed up as a contributor for this section.] -3.3.1. UDP-Lite +3.4.1. Protocol Description - A special class of applications can derive benefit from having - partially-damaged payloads delivered, rather than discarded, when - using paths that include error-prone links. Such applications can - tolerate payload corruption and may choose to use the Lightweight - User Datagram Protocol [RFC3828]. The service may be multicast and/ - or unicast. + UDP is a connection-less datagram protocol, with no connection setup + or feature negotiation. The protocol and API use messages, rather + than a byte-stream. Each stream of messages is independently + managed, therefore retransmission does not hold back data sent using + other logical streams. -3.4. Datagram Congestion Control Protocol (DCCP) + It provides multiplexing to multiple sockets on each host using port + numbers. An active UDP session is identified by its four-tuple of + local and remote IP addresses and local port and remote port numbers. - The Datagram Congestion Control Protocol (DCCP) [RFC4340] is a - bidirectional transport protocol that provides unicast connections of - congestion-controlled unreliable messages. DCCP is suitable for - applications that transfer fairly large amounts of data and that can - benefit from control over the tradeoff between timeliness and - reliability. + UDP fragments packets into IP packets, constrained by the maximum + size of lower layer frame. -3.5. Realtime Transport Protocol (RTP) + Mechanisms for receiver flow control, congestion control, PathMTU + discovery, support for ECN, etc need to be provided by upper layer + protocols [RFC5405]. + + For IPv4 the UDP checksum is optional, but recommended for use in the + general Internet [RFC5405]. [RFC2460] requires the use of this + checksum for IPv6, but [RFC6935] permits this to be relaxed for + specific types of application. The checksum support considerations + for omitting the checksum are defined in [RFC6936]. + + A UDP service may support IPv4 broadcast, multicast, anycast and + unicast. + +3.4.2. Interface Description + + There is no current API specified in the RFC Series, but guidance on + use of common APIs is provided in [RFC5405]. + +3.4.3. Transport Protocol Components + + The transport protocol components provided by UDP are: + + o unicast + + o IPv4 broadcast, multicast and anycast + + o non-reliable, non-ordered delivery + + o message-oriented delivery + o optional checksum protection. + +3.5. Lightweight User Datagram Protocol (UDP-Lite) + + The Lightweight User Datagram Protocol (UDP-Lite) [RFC3828] is an + IETF standards track transport protocol. UDP-Lite provides a + bidirectional set of logical unicast or multicast message streams + over a datagram protocol. IETF guidance on the use of UDP-Lite is + provided in [RFC5405]. + + [EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this + section.] + +3.5.1. Protocol Description + + UDP-Lite is a connection-less datagram protocol, with no connection + setup or feature negotiation. The protocol and API use messages, + rather than a byte-stream. Each stream of messages is independently + managed, therefore retransmission does not hold back data sent using + other logical streams. + + It provides multiplexing to multiple sockets on each host using port + numbers. An active UDP-Lite session is identified by its four-tuple + of local and remote IP addresses and local port and remote port + numbers. + + UDP-Lite fragments packets into IP packets, constrained by the + maximum size of lower layer frame. + + UDP-Lite changes the semantics of the UDP "payload length" field to + that of a "checksum coverage length" field. Otherwise, UDP-Lite is + semantically identical to UDP. Applications using UDP-Lite therefore + can not make assumptions regarding the correctness of the data + received in the insensitive part of the UDP-Lite payload. + + As for UDP, mechanisms for receiver flow control, congestion control, + PathMTU discovery, support for ECN, etc need to be provided by upper + layer protocols [RFC5405]. + + Examples of use include a class of applications that can derive + benefit from having partially-damaged payloads delivered, rather than + discarded. One use is to support are tolerate payload corruption and + over paths that include error-prone links, another application is + when header integrity checks are required but payload integrity is + provided by some other mechanism (e.g. [RFC6936]. + + A UDP-Lite service may support IPv4 broadcast, multicast, anycast and + unicast. + +3.5.2. Interface Description + + There is no current API specified in the RFC Series, but guidance on + use of common APIs is provided in [RFC5405]. + + The interface of UDP-Lite differs from that of UDP by the addition of + a single (socket) option that communicates a checksum coverage length + value: at the sender, this specifies the intended checksum coverage, + with the remaining unprotected part of the payload called the "error- + insensitive part". The checksum coverage may also be made visible to + the application via the UDP-Lite MIB module [RFC5097]. + +3.5.3. Transport Protocol Components + + The transport protocol components provided by UDP-Lite are: + + o unicast + + o IPv4 broadcast, multicast and anycast + + o non-reliable, non-ordered delivery + + o message-oriented delivery + + o partial integrity protection + +3.6. Datagram Congestion Control Protocol (DCCP) + + Datagram Congestion Control Protocol (DCCP) [RFC4340] is an IETF + standards track bidirectional transport protocol that provides + unicast connections of congestion-controlled unreliable messages. + DCCP is suitable for applications that transfer fairly large amounts + of data and that can benefit from control over the trade off between + timeliness and reliability [RFC4336]. + + [EDITOR'S NOTE: Gorry Fairhurst signed up as a contributor for this + section.] + +3.6.1. Protocol Description + + DCCP is a connection-oriented datagram protocol, providing a three + way handshake to allow a client and server to set up a connection, + and mechanisms for orderly completion and immediate teardown of a + connection. The protocol is defined by a family of RFCs. + + It provides multiplexing to multiple sockets on each host using port + numbers. An active DCCP session is identified by its four-tuple of + local and remote IP addresses and local port and remote port numbers. + + At connection setup, DCCP also exchanges the the service code + [RFC5595] mechanism to allow transport instantiations to indicate the + service treatment that is expected from the network. + + The protocol segments data into messages, sized to fit in IP packets, + constrained by the maximum size of lower layer frame. Each message + is identified by a sequence number. The sequence number is used to + identify segments in acknowledgments, to detect unacknowledged + segments, to measure RTT, etc. The protocol may support ordered or + unordered delivery of data, and does not itself provide + retransmission. + + Receiver flow control is supported: limiting the amount of + unacknowledged data that can be outstanding at a given time. + + A DCCP protocol instance can be extended [RFC4340] and tuned. Some + features are sender-side only, requiring no negotiation with the + receiver; some are receiver-side only, some are explicitly negotiated + during connection setup. + + DCCP supports negotiation of the congestion control profile, examples + of specified profiles include [RFC4341] [RFC4342] [RFC5662]. All + IETF-defined methods provide Congestion Control. + + Examples of suitable applications include interactive applications, + streaming media or on-line games [RFC4336]. + + A DCCP service is unicast. + +3.6.2. Interface Description + + There is no current API specified in the RFC Series. + +3.6.3. Transport Protocol Components + + The transport protocol components provided by DCCP are: + + o unicast + + o connection-oriented setup + + o feature negotiation + + o non-reliable, ordered delivery + + o message-oriented delivery + + o partial integrity protection + +3.7. Realtime Transport Protocol (RTP) RTP provides an end-to-end network transport service, suitable for applications transmitting real-time data, such as audio, video or data, over multicast or unicast network services, including TCP, UDP, UDP-Lite, DCCP. [EDITOR'S NOTE: Varun Singh signed up as contributor for this section.] -3.6. Hypertext Transport Protocol (HTTP) as a pseudotransport +3.8. Transport Layer Security (TLS) and Datagram TLS (DTLS) as a + + pseudotransport + + (A few words on TLS [RFC5246] and DTLS [RFC6347] here, and how they + get used by other protocols to meet security goals as an add-on + interlayer above transport.) + +3.8.1. Protocol Description + +3.8.2. Interface Description + +3.8.3. Transport Protocol Components + +3.9. Hypertext Transport Protocol (HTTP) as a pseudotransport [RFC3205] -3.6.1. WebSockets +3.9.1. Protocol Description + +3.9.2. Interface Description + +3.9.3. Transport Protocol Components + +3.10. WebSockets [RFC6455] +3.10.1. Protocol Description + +3.10.2. Interface Description + +3.10.3. Transport Protocol Components 4. Transport Service Features - Features as derived from the subsections above. + (drawn from the candidate features provided by protocol components in + the previous section - please discussion on list) - This section is blank for now. +4.1. Complete Protocol Feature Matrix + + (a comprehensive matrix table goes here; Volunteer: Dave Thaler) 5. IANA Considerations This document has no considerations for IANA. 6. Security Considerations This document surveys existing transport protocols and protocols providing transport-like services. Confidentiality, integrity, and authenticity are among the features provided by those services. This @@ -217,111 +545,168 @@ 7. Contributors Non-editor contributors of text will be listed here, as in the authors section. 8. Acknowledgments This work is partially supported by the European Commission under grant agreement FP7-ICT-318627 mPlane; support does not imply - endorsement. Special thanks to Mirja Kuehlewind for the terminology - section and for leading the terminology discussion in Honolulu. + endorsement. 9. References 9.1. Normative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. - [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 - (IPv6) Specification", RFC 2460, December 1998. - 9.2. Informative References [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [RFC0896] Nagle, J., "Congestion control in IP/TCP internetworks", RFC 896, January 1984. [RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC2018] Mathis, M., Mahdavi, J., Floyd, S., and A. Romanow, "TCP Selective Acknowledgment Options", RFC 2018, October 1996. + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, December 1998. + [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001. [RFC3205] Moore, K., "On the use of HTTP as a Substrate", BCP 56, RFC 3205, February 2002. [RFC3390] Allman, M., Floyd, S., and C. Partridge, "Increasing TCP's Initial Window", RFC 3390, October 2002. [RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P. Conrad, "Stream Control Transmission Protocol (SCTP) Partial Reliability Extension", RFC 3758, May 2004. [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., and G. Fairhurst, "The Lightweight User Datagram Protocol (UDP-Lite)", RFC 3828, July 2004. + [RFC4336] Floyd, S., Handley, M., and E. Kohler, "Problem Statement + for the Datagram Congestion Control Protocol (DCCP)", RFC + 4336, March 2006. + [RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram Congestion Control Protocol (DCCP)", RFC 4340, 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, March 2006. + + [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, + March 2006. + + [RFC4614] Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap + for Transmission Control Protocol (TCP) Specification + Documents", RFC 4614, September 2006. + [RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC 4960, September 2007. + [RFC5097] Renker, G. and G. Fairhurst, "MIB for the UDP-Lite + protocol", RFC 5097, January 2008. + + [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security + (TLS) Protocol Version 1.2", RFC 5246, August 2008. + [RFC5348] Floyd, S., Handley, M., Padhye, J., and J. Widmer, "TCP Friendly Rate Control (TFRC): Protocol Specification", RFC 5348, September 2008. [RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines for Application Designers", BCP 145, RFC 5405, November 2008. + [RFC5595] Fairhurst, G., "The Datagram Congestion Control Protocol + (DCCP) Service Codes", RFC 5595, September 2009. + + [RFC5662] Shepler, S., Eisler, M., and D. Noveck, "Network File + System (NFS) Version 4 Minor Version 1 External Data + Representation Standard (XDR) Description", RFC 5662, + January 2010. + [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, June 2010. [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion Control", RFC 5681, September 2009. [RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the TCP Urgent Mechanism", RFC 6093, January 2011. [RFC6298] Paxson, V., Allman, M., Chu, J., and M. Sargent, "Computing TCP's Retransmission Timer", RFC 6298, June 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. + [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 6455, December 2011. + [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer + Security Version 1.2", RFC 6347, January 2012. + [RFC6691] Borman, D., "TCP Options and Maximum Segment Size (MSS)", RFC 6691, July 2012. + [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, + "TCP Extensions for Multipath Operation with Multiple + Addresses", RFC 6824, January 2013. + [RFC7323] Borman, D., Braden, B., Jacobson, V., and R. Scheffenegger, "TCP Extensions for High Performance", RFC 7323, September 2014. + [I-D.ietf-aqm-ecn-benefits] + Welzl, M. and G. Fairhurst, "The Benefits and Pitfalls of + using Explicit Congestion Notification (ECN)", draft-ietf- + aqm-ecn-benefits-00 (work in progress), October 2014. + Authors' Addresses Godred Fairhurst (editor) University of Aberdeen School of Engineering, Fraser Noble Building Aberdeen AB24 3UE Email: gorry@erg.abdn.ac.uk Brian Trammell (editor) ETH Zurich Gloriastrasse 35 8092 Zurich Switzerland Email: ietf@trammell.ch + + Mirja Kuehlewind (editor) + ETH Zurich + Gloriastrasse 35 + 8092 Zurich + Switzerland + + Email: mirja.kuehlewind@tik.ee.ethz.ch