--- 1/draft-ietf-taps-transports-usage-04.txt 2017-05-24 06:13:33.118824884 -0700 +++ 2/draft-ietf-taps-transports-usage-05.txt 2017-05-24 06:13:33.218827248 -0700 @@ -1,93 +1,96 @@ TAPS M. Welzl Internet-Draft University of Oslo Intended status: Informational M. Tuexen -Expires: October 7, 2017 Muenster Univ. of Appl. Sciences +Expires: November 25, 2017 Muenster Univ. of Appl. Sciences N. Khademi University of Oslo - April 5, 2017 + May 24, 2017 On the Usage of Transport Features Provided by IETF Transport Protocols - draft-ietf-taps-transports-usage-04 + draft-ietf-taps-transports-usage-05 Abstract - This document describes how TCP, MPTCP, SCTP, UDP and UDP-Lite expose - services to applications and how an application can configure and use - the transport features that make up these services. It also - discusses the service provided by the LEDBAT congestion control - mechanism. + This document describes how the transport protocols Transmission + Control Protocol (TCP), MultiPath TCP (MPTCP), Stream Control + Transmission Protocol (SCTP), User Datagram Protocol (UDP) and + Lightweight User Datagram Protocol (UDP-Lite) expose services to + applications and how an application can configure and use the + features that make up these services. It also discusses the service + provided by the Low Extra Delay Background Transport (LEDBAT) + congestion control mechanism. -Status of this Memo +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 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 October 7, 2017. + This Internet-Draft will expire on November 25, 2017. Copyright Notice Copyright (c) 2017 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 carefully, as they describe your rights and restrictions with respect 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. Table of Contents - 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Pass 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3.1. Primitives Provided by TCP . . . . . . . . . . . . . . . . 5 - 3.1.1. Excluded Primitives or Parameters . . . . . . . . . . 8 - 3.2. Primitives Provided by MPTCP . . . . . . . . . . . . . . . 9 + 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 + 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3. Pass 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 + 3.1. Primitives Provided by TCP . . . . . . . . . . . . . . . 5 + 3.1.1. Excluded Primitives or Parameters . . . . . . . . . . 9 + 3.2. Primitives Provided by MPTCP . . . . . . . . . . . . . . 9 3.3. Primitives Provided by SCTP . . . . . . . . . . . . . . . 10 - 3.3.1. Excluded Primitives or Parameters . . . . . . . . . . 17 + 3.3.1. Excluded Primitives or Parameters . . . . . . . . . . 18 3.4. Primitives Provided by UDP and UDP-Lite . . . . . . . . . 18 - 3.5. The service of LEDBAT . . . . . . . . . . . . . . . . . . 18 - 4. Pass 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 4.1. CONNECTION Related Primitives . . . . . . . . . . . . . . 20 - 4.2. DATA Transfer Related Primitives . . . . . . . . . . . . . 31 - 5. Pass 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 - 5.1. CONNECTION Related Transport Features . . . . . . . . . . 34 - 5.2. DATA Transfer Related Transport Features . . . . . . . . . 40 - 5.2.1. Sending Data . . . . . . . . . . . . . . . . . . . . . 40 - 5.2.2. Receiving Data . . . . . . . . . . . . . . . . . . . . 41 - 5.2.3. Errors . . . . . . . . . . . . . . . . . . . . . . . . 41 - 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 42 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 42 - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42 - 9.1. Normative References . . . . . . . . . . . . . . . . . . . 42 - 9.2. Informative References . . . . . . . . . . . . . . . . . . 45 - Appendix A. Overview of RFCs used as input for pass 1 . . . . . . 46 - Appendix B. How this document was developed . . . . . . . . . . . 46 - Appendix C. Revision information . . . . . . . . . . . . . . . . 48 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 49 + 3.5. The service of LEDBAT . . . . . . . . . . . . . . . . . . 19 + 4. Pass 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 + 4.1. CONNECTION Related Primitives . . . . . . . . . . . . . . 21 + 4.2. DATA Transfer Related Primitives . . . . . . . . . . . . 36 + 5. Pass 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 + 5.1. CONNECTION Related Transport Features . . . . . . . . . . 39 + 5.2. DATA Transfer Related Transport Features . . . . . . . . 47 + 5.2.1. Sending Data . . . . . . . . . . . . . . . . . . . . 48 + 5.2.2. Receiving Data . . . . . . . . . . . . . . . . . . . 49 + 5.2.3. Errors . . . . . . . . . . . . . . . . . . . . . . . 50 + 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 50 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 51 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 51 + 9.1. Normative References . . . . . . . . . . . . . . . . . . 51 + 9.2. Informative References . . . . . . . . . . . . . . . . . 54 + Appendix A. Overview of RFCs used as input for pass 1 . . . . . 55 + Appendix B. How this document was developed . . . . . . . . . . 55 + Appendix C. Revision information . . . . . . . . . . . . . . . . 57 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 58 1. Terminology Transport Feature: a specific end-to-end feature that the transport layer provides to an application. Examples include confidentiality, reliable delivery, ordered delivery, message- versus-stream orientation, etc. Transport Service: a set of Transport Features, without an association to any given framing protocol, which provides a complete service to an application. @@ -101,177 +105,182 @@ implements a single transport service, e.g., a protocol stack (RTP over UDP). Application: an entity that uses the transport layer for end-to-end delivery of data across the network (this may also be an upper layer protocol or tunnel encapsulation). Endpoint: an entity that communicates with one or more other endpoints using a transport protocol. Connection: shared state of two or more endpoints that persists across messages that are transmitted between these endpoints. Primitive: a function call that is used to locally communicate - between an application and a transport endpoint and is related to - one or more Transport Features. + between an application and a transport endpoint. A primitive is + related to one or more Transport Features. + Event: a primitive that is invoked by a transport endpoint. Parameter: a value passed between an application and a transport protocol by a primitive. Socket: the combination of a destination IP address and a destination port number. Transport Address: the combination of an IP address, transport protocol and the port number used by the transport protocol. 2. Introduction - This document presents defined interactions between applications and - the transport protocols TCP, MPTCP, SCTP, UDP and UDP-Lite as well as - the LEDBAT congestion control mechanism in the form of primitives and - Transport Features. Primitives can be invoked by an application or a - transport protocol; the latter type is called an "event". The list - of primitives and Transport Features in this document is strictly - based on the parts of protocol specifications that describe what the - protocol provides to an application using it and how the application - interacts with it. Together with [RFC8095], it provides the basis - for the minimal set of transport services that end systems should - support; this minimal set is derived in + This document presents, in the form of primitives, events and + transport features, defined interactions between applications and the + following unicast transport protocols: Transmission Control Protocol + (TCP), MultiPath TCP (MPTCP), Stream Control Transmission Protocol + (SCTP), User Datagram Protocol (UDP), Lightweight User Datagram + Protocol (UDP-Lite). It also defines a primitive to enable/disable + and configure the Low Extra Delay Background Transport (LEDBAT) + unicast congestion control mechanism. Transport protocols provide + communication between processes that operate on network endpoints, + which means that they allow for multiplexing of communication between + the same IP addresses, and normally this multiplexing is achieved + using port numbers. Port multiplexing is therefore assumed to be + always provided and not discussed in this document. + + The list of primitives, events and transport features in this + document is strictly based on the parts of protocol specifications + that describe what the protocol provides to an application using it + and how the application interacts with it. Together with an overview + of the services provided by IETF transport protocols and congestion + control mechanisms [RFC8095] and an analysis of UDP and UDP-Lite + [FJ16], it provides the basis for the minimal set of transport + services that end systems should support [I-D.draft-gjessing-taps-minset]. Parts of a protocol that are explicitly stated as optional to implement are not covered. Interactions between the application and a transport protocol that are not directly related to the operation - of the protocol are also not covered. For example, [RFC6458] - explains how an application can use socket options to indicate its - interest in receiving certain notifications. However, for the - purpose of identifying primitives and Transport Services, the ability - to enable or disable the reception of notifications is irrelevant. - Similarly, one-to-many style sockets described in [RFC6458] just + of the protocol are also not covered. For example, there are various + ways for an application to use socket options to indicate its + interest in receiving certain notifications [RFC6458]. However, for + the purpose of identifying primitives, events and transport features, + the ability to enable or disable the reception of notifications is + irrelevant. Similarly, "one-to-many style sockets" [RFC6458] just affect the application programming style, not how the underlying protocol operates, and they are therefore not discussed here. The same is true for the ability to obtain the unchanged value of a - parameter that an application has previously set (this is the case - for the "get" in many get/set operations in [RFC6458]). + parameter that an application has previously set (e.g.,via "get" in + get/set operations [RFC6458]). The document presents a three-pass process to arrive at a list of - Transport Features. In the first pass, the relevant RFC text is + transport features. In the first pass, the relevant RFC text is discussed per protocol. In the second pass, this discussion is used - to derive a list of primitives that are uniformly categorized across - protocols. Here, an attempt is made to present or -- where text - describing primitives does not yet exist -- construct primitives in a - slightly generalized form to highlight similarities. This is, for - example, achieved by renaming primitives of protocols or by avoiding - a strict 1:1-mapping between the primitives in the protocol - specification and primitives in the list. Finally, the third pass - presents Transport Features based on pass 2, identifying which - protocols implement them. + to derive a list of primitives and events that are uniformly + categorized across protocols. Here, an attempt is made to present or + -- where text describing primitives or events does not yet exist -- + construct primitives or events in a slightly generalized form to + highlight similarities. This is, for example, achieved by renaming + primitives or events of protocols or by avoiding a strict 1:1-mapping + between the primitives or events in the protocol specification and + primitives or events in the list. Finally, the third pass presents + transport features based on pass 2, identifying which protocols + implement them. - In the list resulting from the second pass, some Transport Features + In the list resulting from the second pass, some transport features are missing because they are implicit in some protocols, and they - only become explicit when we consider the superset of all features - offered by all protocols. For example, TCP always carries out - congestion control; we have to consider it together with a protocol - like UDP (which does not have congestion control) before we can - consider congestion control as a Transport Feature. The complete - list of features across all protocols is therefore only available - after pass 3. - - This document discusses unicast transport protocols and a unicast - congestion control mechanism. Transport protocols provide - communication between processes that operate on network endpoints, - which means that they allow for multiplexing of communication between - the same IP addresses, and normally this multiplexing is achieved - using port numbers. Port multiplexing is therefore assumed to be - always provided and not discussed in this document. + only become explicit when we consider the superset of all transport + features offered by all protocols. For example, TCP always carries + out congestion control; we have to consider it together with a + protocol like UDP (which does not have congestion control) before we + can consider congestion control as a transport feature. The complete + list of transport features across all protocols is therefore only + available after pass 3. Some protocols are connection-oriented. Connection-oriented - protocols often use an initial call to a specific transport primitive - to open a connection before communication can progress, and require + protocols often use an initial call to a specific primitive to open a + connection before communication can progress, and require communication to be explicitly terminated by issuing another call to - a transport primitive (usually called "close"). A "connection" is - the common state that some transport primitives refer to, e.g., to - adjust general configuration settings. Connection establishment, + a primitive (usually called "close"). A "connection" is the common + state that some transport primitives refer to, e.g., to adjust + general configuration settings. Connection establishment, maintenance and termination are therefore used to categorize transport primitives of connection-oriented transport protocols in pass 2 and pass 3. For this purpose, UDP is assumed to be used with "connected" sockets, i.e. sockets that are bound to a specific pair of addresses and ports [FJ16]. 3. Pass 1 This first iteration summarizes the relevant text parts of the RFCs describing the protocols, focusing on what each transport protocol provides to the application and how it is used (abstract API descriptions, where they are available). 3.1. Primitives Provided by TCP - [RFC0793] states: "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". Section 3.8 in [RFC0793] - further specifies the interaction with the application by listing - several transport primitives. It is also assumed that an Operating - System provides a means for TCP to asynchronously signal the - application; the primitives representing such signals are called - 'events' in this section. This section describes the relevant - primitives. + The initial TCP specification [RFC0793] states: "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". Section 3.8 in this specification [RFC0793] further + specifies the interaction with the application by listing several + transport primitives. It is also assumed that an Operating System + provides a means for TCP to asynchronously signal the application; + the primitives representing such signals are called 'events' in this + section. This section describes the relevant primitives. open: this is either active or passive, to initiate a connection or listen for incoming connections. All other primitives are associated with a specific connection, which is assumed to first have been opened. An active open call contains a socket. A passive open call with a socket waits for a particular connection; alternatively, a passive open call can leave the socket unspecified to accept any incoming connection. A fully specified passive call can later be made active by calling 'send'. Optionally, a timeout can be specified, after which TCP will abort the connection if data has not been successfully delivered to the - destination (else a default timeout value is used). [RFC1122] - describes a procedure for aborting the connection that must be - used to avoid excessive retransmissions, and states that an - application must be able to control the threshold used to - determine the condition for aborting -- and that this threshold - may be measured in time units or as a count of retransmission. - This indicates that the timeout could also be specified as a count - of retransmission. + destination (else a default timeout value is used). A procedure + for aborting the connection is used to avoid excessive + retransmissions, and an application is able to control the + threshold used to determine the condition for aborting; this + threshold may be measured in time units or as a count of + retransmission [RFC1122]. This indicates that the timeout could + also be specified as a count of retransmission. Also optional, for multihomed hosts, the local IP address can be provided [RFC1122]. If it is not provided, a default choice will be made in case of active open calls. A passive open call will await incoming connection requests to all local addresses and then maintain usage of the local IP address where the incoming connection request has arrived. Finally, the 'options' parameter - is explained in [RFC1122] to allow the application to specify IP - options such as source route, record route, or timestamp. It is - not stated on which segments of a connection these options should - be applied, but probably all segments, as this is also stated in a - specification given for the usage of source route (section 4.2.3.8 - of [RFC1122]). Source route is the only non-optional IP option in + allows the application to specify IP options such as source route, + record route, or timestamp [RFC1122]. It is not stated on which + segments of a connection these options should be applied, but + probably all segments, as this is also stated in a specification + given for the usage of source route (section 4.2.3.8 of + [RFC1122]). Source route is the only non-optional IP option in this parameter, allowing an application to specify a source route when it actively opens a TCP connection. Master Key Tuples (MKTs) for authentication can optionally be - configured when calling open (section 7.1 of [RFC5925]). + configured when calling open (section 7.1 of [RFC5925]). When + authentication is in use, complete TCP segments are authenticated, + including the TCP IPv4 pseudoheader, TCP header, and TCP data. TCP Fast Open (TFO) [RFC7413] allows to immediately hand over a message from the active open to the passive open side of a TCP connection together with the first message establishment packet (the SYN). This can be useful for applications that are sensitive to TCP's connection setup delay. TCP implementations MUST NOT use TFO by default, but only use TFO if requested explicitly by the - application on a per-service-port basis. To benefit from TFO, the - first application data unit (e.g., an HTTP request) needs to be no - more than TCP's maximum segment size (minus options used in the - SYN). For the active open side, [RFC7413] recommends changing or - replacing the connect() call in order to support a user data - buffer argument. For the passive open side, the application needs - to enable the reception of Fast Open requests, e.g. via a new - TCP_FASTOPEN setsockopt() socket option before listen(). The - receiving application must be prepared to accept duplicates of the - TFO message, as the first data written to a socket can be - delivered more than once to the application on the remote host. + application on a per-service-port basis. more than TCP's maximum + segment size (minus options used in the SYN). For the active open + side, it is recommended to change or replace the connect() call in + order to support a user data buffer argument [RFC7413]. For the + passive open side, the application needs to enable the reception + of Fast Open requests, e.g. via a new TCP_FASTOPEN setsockopt() + socket option before listen(). The receiving application must be + prepared to accept duplicates of the TFO message, as the first + data written to a socket can be delivered more than once to the + application on the remote host. send: this is the primitive that an application uses to give the local TCP transport endpoint a number of bytes that TCP should reliably send to the other side of the connection. The URGENT flag, if set, states that the data handed over by this send call is urgent and this urgency should be indicated to the receiving process in case the receiving application has not yet consumed all non-urgent data preceding it. An optional timeout parameter can be provided that updates the connection's timeout (see 'open'). Additionally, optional parameters allow to indicate the preferred @@ -302,247 +311,251 @@ close event: TCP uses this primitive to inform an application that the application on the other side has called the 'close' primitive, so the local application can also issue a 'close' and terminate the connection gracefully. See [RFC0793], Section 3.5. abort event: When TCP aborts a connection upon receiving a "Reset" from the peer, it "advises the user and goes to the CLOSED state." See [RFC0793], Section 3.4. - USER TIMEOUT event: This event, described in Section 3.9 of - [RFC0793], is executed when the user timeout expires (see 'open'). - All queues are flushed and the application is informed that the - connection had to be aborted due to user timeout. + USER TIMEOUT event: This event is executed when the user timeout + expires (see 'open') (section 3.9 of [RFC0793]). All queues are + flushed and the application is informed that the connection had to + be aborted due to user timeout. - ERROR_REPORT event: This event, described in Section 4.2.4.1 of - [RFC1122], informs the application of "soft errors" that can be - safely ignored [RFC5461], including the arrival of an ICMP error - message or excessive retransmissions (reaching a threshold below - the threshold where the connection is aborted). + ERROR_REPORT event: This event informs the application of "soft + errors" that can be safely ignored [RFC5461], including the + arrival of an ICMP error message or excessive retransmissions + (reaching a threshold below the threshold where the connection is + aborted). See section 4.2.4.1 of [RFC1122]. - Type-of-Service: Section 4.2.4.2 of [RFC1122] states that the - application layer MUST be able to specify the Type-of-Service - (TOS) for segments that are sent on a connection. The application - should be able to change the TOS during the connection lifetime, - and the TOS value should be passed to the IP layer unchanged. - Since then the TOS field has been redefined. A part of the field - has been assigned to ECN [RFC3168] and the six most significant - bits have been assigned to carry the DiffServ CodePoint, DSField - [RFC3260]. Staying with the intention behind the application's - ability to specify the "Type of Service", this should probably be - interpreted to mean the value in the DSField, which is the - Differentiated Services Codepoint (DSCP). + Type-of-Service: Section 4.2.4.2 of the requirements for Internet + hosts [RFC1122] states that the application layer MUST be able to + specify the Type-of-Service (TOS) for segments that are sent on a + connection. The application should be able to change the TOS + during the connection lifetime, and the TOS value should be passed + to the IP layer unchanged. Since then the TOS field has been + redefined. The Differentiated Services (diffuser) model [RFC2475] + [RFC3260] replaces this field in the IP Header, assigning the six + most significant bits to carry the Differentiated Services Code + Point (DSCP) field [RFC2474]. - Nagle: The Nagle algorithm, described in Section 4.2.3.4 of - [RFC1122], delays sending data for some time to increase the - likelihood of sending a full-sized segment. An application can - disable the Nagle algorithm for an individual connection. + Nagle: The Nagle algorithm delays sending data for some time to + increase the likelihood of sending a full-sized segment (section + 4.2.3.4 of [RFC1122]). An application can disable the Nagle + algorithm for an individual connection. User Timeout Option: The User Timeout Option (UTO) [RFC5482] allows one end of a TCP connection to advertise its current user timeout value so that the other end of the TCP connection can adapt its own user timeout accordingly. In addition to the configurable - value of the User Timeout (see 'send'), [RFC5482] introduces three - per-connection state variables that an application can adjust to + value of the User Timeout (see 'send'), there are three per- + connection state variables that an application can adjust to control the operation of the User Timeout Option (UTO): ADV_UTO is the value of the UTO advertised to the remote TCP peer (default: system-wide default user timeout); ENABLED (default false) is a boolean-type flag that controls whether the UTO option is enabled for a connection. This applies to both sending and receiving. CHANGEABLE is a boolean-type flag (default true) that controls whether the user timeout may be changed based on a UTO option received from the other end of the connection. CHANGEABLE becomes false when an application explicitly sets the user timeout (see 'send'). -3.1.1. Excluded Primitives or Parameters + Set / Get Authentication Parameters: The preferred outgoing MKT + (current_key) and/or the preferred incoming MKT (rnext_key) of a + connection can be configured. Information about current_key and + rnext_key carried in a recently received segment can be retrieved + (section 7.1 of [RFC5925]). - The 'open' primitive specified in [RFC0793] can be handed optional - Precedence or security/compartment information according to - [RFC0793], but this was not included here because it is mostly - irrelevant today, as explained in [RFC7414]. +3.1.1. Excluded Primitives or Parameters - The 'status' primitive was not included because [RFC0793] describes - this primitive as "implementation dependent" and states that it - "could be excluded without adverse effect". Moreover, while a data - block containing specific information is described, it is also stated - that not all of this information may always be available. While + The 'open' primitive can be handed optional Precedence or security/ + compartment information [RFC0793], but this was not included here + because it is mostly irrelevant today [RFC7414]. - [RFC5925] states that 'status' SHOULD be augmented to allow the MKTs - of a current or pending connection to be read (for confirmation), the - same information is also available via 'receive', which MUST be - augmented with that functionality according to [RFC5925]. The 'send' - primitive described in [RFC0793] includes an optional PUSH flag - which, if set, requires data to be promptly transmitted to the - receiver without delay; the 'receive' primitive described in - [RFC0793] can (under some conditions) yield the status of the PUSH - flag. Because PUSH functionality is made optional to implement for - both the 'send' and 'receive' primitives in [RFC1122], this - functionality is not included here. [RFC1122] also introduces keep- - alives to TCP, but these are optional to implement and hence not - considered here. [RFC1122] describes that "some TCP implementations - have included a FLUSH call", indicating that this call is also - optional to implement. It is therefore not considered here. + The 'status' primitive was not included because the initial TCP + specification describes this primitive as "implementation dependent" + and states that it "could be excluded without adverse effect" + [RFC0793]. Moreover, while a data block containing specific + information is described, it is also stated that not all of this + information may always be available. While 'status' SHOULD be + augmented to allow the MKTs of a current or pending connection to be + read (for confirmation), the same information is also available via + 'receive', which MUST be augmented with that functionality [RFC5925]. + The 'send' primitive includes an optional PUSH flag which, if set, + requires data to be promptly transmitted to the receiver without + delay [RFC0793]; the 'receive' primitive described in can (under some + conditions) yield the status of the PUSH flag. Because PUSH + functionality is optional to implement for both the 'send' and + 'receive' primitives [RFC1122], this functionality is not included + here. The requirements for Internet hosts [RFC1122] also introduce + keep-alives to TCP, but these are optional to implement and hence not + considered here. The same document also describes that "some TCP + implementations have included a FLUSH call", indicating that this + call is also optional to implement. It is therefore not considered + here. 3.2. Primitives Provided by MPTCP Multipath TCP (MPTCP) is an extension to TCP that allows the use of multiple paths for a single data-stream. It achieves this by creating different so-called TCP subflows for each of the interfaces and scheduling the traffic across these TCP subflows. The service - provided by MPTCP is described in [RFC6182] "Multipath TCP MUST - follow the same service model as TCP [RFC0793]: in- order, reliable, - and byte-oriented delivery. Furthermore, a Multipath TCP connection - SHOULD provide the application with no worse throughput or resilience - than it would expect from running a single TCP connection over any - one of its available paths." + provided by MPTCP is described as follows [RFC6182]: "Multipath TCP + MUST follow the same service model as TCP [RFC0793]: in- order, + reliable, and byte-oriented delivery. Furthermore, a Multipath TCP + connection SHOULD provide the application with no worse throughput or + resilience than it would expect from running a single TCP connection + over any one of its available paths." - Further, [RFC6182] states constraints on the API exposed by MPTCP: "A - multipath-capable equivalent of TCP MUST retain some level of - backward compatibility with existing TCP APIs, so that existing - applications can use the newer merely by upgrading the operating - systems of the end hosts." As such, the primitives provided by MPTCP - are equivalent to the ones provided by TCP. Nevertheless, [RFC6824] - and [RFC6897] clarify some parts of TCP's primitives with respect to - MPTCP and add some extensions for better control on MPTCP's subflows. - Hereafter is a list of the clarifications and extensions the above - cited RFCs provide to TCP's primitives. + Further, there are some constraints on the API exposed by MPTCP + [RFC6182]: "A multipath-capable equivalent of TCP MUST retain some + level of backward compatibility with existing TCP APIs, so that + existing applications can use the newer merely by upgrading the + operating systems of the end hosts." As such, the primitives + provided by MPTCP are equivalent to the ones provided by TCP. + Nevertheless, the MPTCP RFCs [RFC6824] and [RFC6897] clarify some + parts of TCP's primitives with respect to MPTCP and add some + extensions for better control on MPTCP's subflows. Hereafter is a + list of the clarifications and extensions the above cited RFCs + provide to TCP's primitives. - open: [RFC6897] states "An application should be able to request to - turn on or turn off the usage of MPTCP.". The RFC states that - this functionality can be provided through a socket-option called - TCP_MULTIPATH_ENABLE. Further, [RFC6897] says that MPTCP must be - disabled in case the application is binding to a specific address. + open: "An application should be able to request to turn on or turn + off the usage of MPTCP" [RFC6897]. This functionality can be + provided through a socket-option called TCP_MULTIPATH_ENABLE. + Further, MPTCP must be disabled in case the application is binding + to a specific address [RFC6897]. - send/receive: [RFC6824] states that the sending and receiving of - data does not require any changes to the application when MPTCP is - being used. The MPTCP-layer will "take one input data stream from - an application, and split it into one or more subflows, with + send/receive: The sending and receiving of data does not require any + changes to the application when MPTCP is being used [RFC6824]. + The MPTCP-layer will "take one input data stream from an + application, and split it into one or more subflows, with sufficient control information to allow it to be reassembled and delivered reliably and in order to the recipient application." - The use of the Urgent-Pointer is special in MPTCP and [RFC6824] - says "a TCP subflow MUST NOT use the Urgent Pointer to interrupt - an existing mapping." + The use of the Urgent-Pointer is special in MPTCP [RFC6824]: "a + TCP subflow MUST NOT use the Urgent Pointer to interrupt an + existing mapping." address and subflow management: MPTCP uses different addresses and allows a host to announce these addresses as part of the protocol. - [RFC6897] says "An application should be able to restrict MPTCP to - binding to a given set of addresses." and thus allows applications - to limit the set of addresses that are being used by MPTCP. - Further, "An application should be able to obtain information on - the pairs of addresses used by the MPTCP subflows.". + The MPTCP API Considerations RFC [RFC6897] says "An application + should be able to restrict MPTCP to binding to a given set of + addresses" and thus allows applications to limit the set of + addresses that are being used by MPTCP. Further, "An application + should be able to obtain information on the pairs of addresses + used by the MPTCP subflows". 3.3. Primitives Provided by SCTP - Section 1.1 of [RFC4960] lists limitations of TCP that SCTP removes. - Three of the four mentioned limitations directly translate into - Transport Features that are visible to an application using SCTP: 1) - it allows for preservation of message delineations; 2) these - messages, while reliably transferred, do not require to be in order - unless the application wants it; 3) multi-homing is supported. In - SCTP, connections are called "associations" and they can be between - not only two (as in TCP) but multiple addresses at each endpoint. + TCP has a number of limitations that SCPT removes (section 1.1 of + [RFC4960]). The following three removed limitations directly + translate into transport features that are visible to an application + using SCTP: 1) it allows for preservation of message delineations; 2) + these messages, while reliably transferred, do not require to be in + order unless the application wants it; 3) multi-homing is supported. + In SCTP, connections are called "associations" and they can be + between not only two (as in TCP) but multiple addresses at each + endpoint. - Section 10 of [RFC4960] further specifies the interaction with the - application (which RFC [RFC4960] calls the "Upper Layer Protocol" - (ULP)). It is assumed that the Operating System provides a means for - SCTP to asynchronously signal the application; the primitives - representing such signals are called 'events' in this section. Here, - we describe the relevant primitives. In addition to the abstract API - described in Section 10 of [RFC4960], an extension to the socket API - is described in [RFC6458], covering the functionality of the base - protocol specified in [RFC4960] and its extensions specified in - [RFC3758], [RFC4895], and [RFC5061]. For the protocol extensions - specified in [RFC6525], [RFC6951], [RFC7053], [RFC7496], [RFC7829] - and [I-D.ietf-tsvwg-sctp-ndata], the corresponding extensions of the + Section 10 of the SCTP base protocol specification [RFC4960] + specifies the interaction with the application (which this RFC calls + the "Upper Layer Protocol" (ULP)). It is assumed that the Operating + System provides a means for SCTP to asynchronously signal the + application; the primitives representing such signals are called + 'events' in this section. Here, we describe the relevant primitives. + In addition to the abstract API described in the section 10 of the + SCTP base protocol specification [RFC4960], an extension to the + socket API is described in [RFC6458]. This covers the functionality + of the base protocol [RFC4960] and some of its extensions [RFC3758], + [RFC4895], [RFC5061]. For other protocol extensions [RFC6525], + [RFC6951], [RFC7053], [RFC7496], [RFC7829], + [I-D.ietf-tsvwg-sctp-ndata], the corresponding extensions of the socket API are specified in these protocol specifications. The - functionality exposed to the ULP through this socket API is - considered here in addition to the abstract API specified in Section - 10 of [RFC4960]. + functionality exposed to the ULP through the all these APIs is + considered here. - [RFC4960] contains a "SETPROTOCOLPARAMETERS" primitive that allows to - adjust elements of a parameter list; it is stated that SCTP - implementations "may allow ULP to customize some of these protocol - parameters", indicating that none of the elements of this parameter - list are mandatory to make ULP-configurable. Thus, we only consider - the parameters in [RFC4960] that are also covered in one of the other - RFCs listed above, which leads us to exclude the parameters - RTO.Alpha, RTO.Beta and HB.Max.Burst. For clarity, we also replace - "SETPROTOCOLPARAMETERS" itself with primitives that adjust parameters - or groups of parameters which fit together. + The abstract API contains a "SETPROTOCOLPARAMETERS" primitive that + allows to adjust elements of a parameter list [RFC4960]; it is stated + that SCTP implementations "may allow ULP to customize some of these + protocol parameters", indicating that none of the elements of this + parameter list are mandatory to make ULP-configurable. Thus, we only + consider the parameters in the abstract API that are also covered in + one of the other RFCs listed above, which leads us to exclude the + parameters RTO.Alpha, RTO.Beta and HB.Max.Burst. For clarity, we + also replace "SETPROTOCOLPARAMETERS" itself with primitives that + adjust parameters or groups of parameters which fit together. - Initialize: Initialize, described in [RFC4960], creates a local SCTP - instance that it binds to a set of local addresses (and, if - provided, port number). Initialize needs to be called only once - per set of local addresses. [RFC6458] also describes a number of - per-association initialization parameters that can be used when an - association is created, but before it is connected (via the - primitive 'Associate' below): the maximum number of inbound - streams the application is prepared to support, the maximum number - of attempts to be made when sending the INIT (the first message of - association establishment), and the maximum retransmission timeout - (RTO) value to use when attempting an INIT. At this point, before + Initialize: Initialize creates a local SCTP instance that it binds + to a set of local addresses (and, if provided, a local port + number) [RFC4960]. Initialize needs to be called only once per + set of local addresses. A number of per-association + initialization parameters can be used when an association is + created, but before it is connected (via the primitive 'Associate' + below): the maximum number of inbound streams the application is + prepared to support, the maximum number of attempts to be made + when sending the INIT (the first message of association + establishment), and the maximum retransmission timeout (RTO) value + to use when attempting an INIT [RFC6458]. At this point, before connecting, an application can also enable UDP encapsulation by configuring the remote UDP encapsulation port number [RFC6951]. Associate: This creates an association (the SCTP equivalent of a connection) that connects the local SCTP instance and a remote SCTP instance. To identify the remote endpoint, it can be given - one or multiple (using connectx as described in section 9.9 of - [RFC6458]) sockets. Most primitives are associated with a - specific association, which is assumed to first have been created. + one or multiple (using "connectx") sockets (section 9.9 of + [RFC6458]). Most primitives are associated with a specific + association, which is assumed to first have been created. Associate can return a list of destination transport addresses so that multiple paths can later be used. One of the returned sockets will be selected by the local endpoint as default primary path for sending SCTP packets to this peer, but this choice can be changed by the application using the list of destination addresses. Associate is also given the number of outgoing streams to request and optionally returns the number of negotiated outgoing streams. An optional parameter of 32 bits, the - adaptation layer indication, can be provided, as specified in - [RFC5061]. If the extension specified in [RFC4895] is used, the - chunk types required to be sent authenticated by the peer can be - provided. [RFC6458] describes a 'SCTP_CANT_STR_ASSOC' - notification that is used to inform the application of a failure - to create an association. [RFC6458] describes how an application - could use sendto() or sendmsg() to implicitly setup an + adaptation layer indication, can be provided [RFC5061]. If + authenticated chunks are used, the chunk types required to be sent + authenticated by the peer can be provided [RFC4895]. A + 'SCTP_CANT_STR_ASSOC' notification is used to inform the + application of a failure to create an association [RFC6458]. An + application could use sendto() or sendmsg() to implicitly setup an association, thereby handing over a message that SCTP might send - during the association setup phase. Note that this mechanism is - different from TCP's TFO mechanism: the message would arrive only - once, after at least one RTT, as it is sent together with the - third message exchanged during association setup, the COOKIE-ECHO - chunk). + during the association setup phase [RFC6458]. Note that this + mechanism is different from TCP's TFO mechanism: the message would + arrive only once, after at least one RTT, as it is sent together + with the third message exchanged during association setup, the + COOKIE-ECHO chunk). Send: This sends a message of a certain length in bytes over an association. A number can be provided to later refer to the correct message when reporting an error, and a stream id is provided to specify the stream to be used inside an association (we consider this as a mandatory parameter here for simplicity: if not provided, the stream id defaults to 0). A condition to abandon the message can be specified (for example limiting the number of retransmissions or the lifetime of the user message). - This allows to control the partial reliability extension specified - in [RFC3758] and [RFC7496]. An optional maximum life time can - specify the time after which the message should be discarded - rather than sent. A choice (advisory, i.e. not guaranteed) of the - preferred path can be made by providing a socket, and the message - can be delivered out-of-order if the unordered flag is set. An - advisory flag indicates that the peer should not delay the - acknowledgement of the user message provided by making use of the - I-bit specified in [RFC7053]. Another advisory flag indicates - whether the application prefers to avoid bundling user data with - other outbound DATA chunks (i.e., in the same packet). A payload - protocol-id can be provided to pass a value that indicates the - type of payload protocol data to the peer. If the extension - specified in [RFC4895] is used, the key identifier used for - authenticating the DATA chunks can be provided. + This allows to control the partial reliability extension + [RFC3758], [RFC7496]. An optional maximum life time can specify + the time after which the message should be discarded rather than + sent. A choice (advisory, i.e. not guaranteed) of the preferred + path can be made by providing a socket, and the message can be + delivered out-of-order if the unordered flag is set. An advisory + flag indicates that the peer should not delay the acknowledgement + of the user message provided [RFC7053]. Another advisory flag + indicates whether the application prefers to avoid bundling user + data with other outbound DATA chunks (i.e., in the same packet). + A payload protocol-id can be provided to pass a value that + indicates the type of payload protocol data to the peer. If + authenticated chunks are used, the key identifier for + authenticating DATA chunks can be provided [RFC4895]. Receive: Messages are received from an association, and optionally a stream within the association, with their size returned. The application is notified of the availability of data via a DATA ARRIVE notification. If the sender has included a payload protocol-id, this value is also returned. If the received message is only a partial delivery of a whole message, a partial flag will indicate so, in which case the stream id and a stream sequence number are provided to the application. A delivery number lets the application detect reordering. @@ -558,83 +571,81 @@ was aborted. Optionally, an abort reason to be passed to the peer may be provided by the application. A return code informs about success or failure of this procedure. Change Heartbeat / Request Heartbeat: This allows the application to enable/disable heartbeats and optionally specify a heartbeat frequency as well as requesting a single heartbeat to be carried out upon a function call, with a notification about success or failure of transmitting the HEARTBEAT chunk to the destination. - Configure Max. Retransmissions of an Association: The parameter - Association.Max.Retrans in [RFC4960], called sasoc_maxrxt in - [RFC6458], allows to configure the number of unsuccessful - retransmissions after which an entire association is considered as - failed (which should invoke a COMMUNICATION LOST notification). + Configure Max. Retransmissions of an Association: The parameter Asso + ciation.Max.Retrans [RFC4960] (called "sasoc_maxrxt" in the SCTP + socket API extensions [RFC6458]), allows to configure the number + of unsuccessful retransmissions after which an entire association + is considered as failed; this should invoke a COMMUNICATION LOST + notification. Set Primary: This allows to set a new primary default path for an association by providing a socket. Optionally, a default source address to be used in IP datagrams can be provided. Change Local Address / Set Peer Primary: This allows an endpoint to add/remove local addresses to/from an association. In addition, the peer can be given a hint which address to use as the primary - address. This is provided by the protocol extension defined in - [RFC5061]. + address [RFC5061]. - Configure Path Switchover: [RFC4960] contains a primitive called SET - FAILURE THRESHOLD. This configures the parameter - "Path.Max.Retrans", which determines after how many + Configure Path Switchover: The abstract API contains a primitive + called SET FAILURE THRESHOLD [RFC4960]. This configures the + parameter "Path.Max.Retrans", which determines after how many retransmissions a particular transport address is considered as unreachable. If there are more transport addresses available in an association, reaching this limit will invoke a path switchover. - [RFC7829] extends this method with a concept of "Potentially - Failed" (PF) paths. When a path is in PF state, SCTP will not - entirely give up sending on that path, but it will preferably send - data on other active paths if such paths are available. Entering - the PF state is done upon exceeding a configured maximum number of - retransmissions. Thus, for all paths where this mechanism is - used, there are two configurable error thresholds: one to decide - that a path is in PF state, and one to decide that the transport - address is unreachable. + An extension called "SCTP-PF" adds a concept of "Potentially + Failed" (PF) paths to this method [RFC7829]. When a path is in PF + state, SCTP will not entirely give up sending on that path, but it + will preferably send data on other active paths if such paths are + available. Entering the PF state is done upon exceeding a + configured maximum number of retransmissions. Thus, for all paths + where this mechanism is used, there are two configurable error + thresholds: one to decide that a path is in PF state, and one to + decide that the transport address is unreachable. Set / Get Authentication Parameters: This allows an endpoint to add/ remove key material to/from an association. In addition, the - chunk types being authenticated can be queried. This is provided - by the protocol extension defined in [RFC4895]. + chunk types being authenticated can be queried [RFC4895]. Add / Reset Streams, Reset Association: This allows an endpoint to add streams to an existing association or or to reset them - individually. Additionally, the association can be reset. This - is provided by the protocol extension defined in [RFC6525]. + individually. Additionally, the association can be reset + [RFC6525]. Status: The 'Status' primitive returns a data block with information about a specified association, containing: association connection state; destination transport address list; destination transport address reachability states; current local and peer receiver window sizes; current local congestion window sizes; number of unacknowledged DATA chunks; number of DATA chunks pending receipt; primary path; most recent SRTT on primary path; RTO on primary path; SRTT and RTO on other destination addresses [RFC4960] and MTU per path [RFC6458]. Enable / Disable Interleaving: This allows to enable or disable the negotiation of user message interleaving support for future associations. For existing associations it is possible to query whether user message interleaving support was negotiated or not on a particular association [I-D.ietf-tsvwg-sctp-ndata]. Set Stream Scheduler: This allows to select a stream scheduler per association, with a choice of: First Come First Serve, Round Robin, Round Robin per Packet, Priority Based, Fair Bandwidth, - Weighted Fair Queuing. How these schedulers operate is described - in detail in [I-D.ietf-tsvwg-sctp-ndata]. + Weighted Fair Queuing [I-D.ietf-tsvwg-sctp-ndata]. Configure Stream Scheduler: This allows to change a parameter per stream for the schedulers: a priority value for the Priority Based scheduler and a weight for the Weighted Fair Queuing scheduler. Enable/disable NODELAY: This turns on/off any Nagle-like algorithm for an association [RFC6458]. Configure send buffer size: This controls the amount of data SCTP may have waiting in internal buffers to be sent or retransmitted @@ -644,53 +655,53 @@ octets, thereby controlling the receiver window for an association [RFC6458]. Configure message fragmentation: If a user message causes an SCTP packet to exceed the maximum fragmentation size (which can be provided by the application, and is otherwise the PMTU size), then the message will be fragmented by SCTP. Disabling message fragmentation will produce an error instead of fragmenting the message [RFC6458]. - Configure Path MTU Discovery: Section 8.1.12 of [RFC6458] explains - how Path MTU Discovery can be enabled or disabled per peer address - of an association. When it is enabled, the current Path MTU value - can be obtained. When it is disabled, the Path MTU to be used can - be controlled by the application. + Configure Path MTU Discovery: Path MTU Discovery can be enabled or + disabled per peer address of an association (section 8.1.12 of + [RFC6458]). When it is enabled, the current Path MTU value can be + obtained. When it is disabled, the Path MTU to be used can be + controlled by the application. Configure delayed SACK timer: The time before sending a SACK can be adjusted; delaying SACKs can be disabled; the number of packets that must be received before a SACK is sent without waiting for the delay timer to expire can be configured [RFC6458]. - Set Cookie life value: The Cookie life value can be adjusted as - explained in Section 8.1.2 of [RFC6458]. "Valid.Cookie.Life" is - also one of the parameters listed as potentially adjustable with - SETPROTOCOLPARAMETERS in [RFC4960]. + Set Cookie life value: The Cookie life value can be adjusted + (section 8.1.2 of [RFC6458]). "Valid.Cookie.Life" is also one of + the parameters that is potentially adjustable with + SETPROTOCOLPARAMETERS [RFC4960]. Set maximum burst: The maximum burst of packets that can be emitted by a particular association (default 4, and values above 4 are - optional to implement) can be adjusted as explained in Section - 8.1.2 of [RFC6458]. "Max.Burst" is also one of the parameters - listed as potentially adjustable with SETPROTOCOLPARAMETERS in - [RFC4960]. + optional to implement) can be adjusted (section 8.1.2 of + [RFC6458]). "Max.Burst" is also one of the parameters that is + potentially adjustable with SETPROTOCOLPARAMETERS [RFC4960]. - Configure RTO calculation: [RFC4960] lists the following adjustable - parameters: RTO.Initial; RTO.Min; RTO.Max; RTO.Alpha; RTO.Beta. - Only the initial, minimum and maximum RTO are also described as - configurable [RFC6458]. + Configure RTO calculation: The abstract API contains the following + adjustable parameters: RTO.Initial; RTO.Min; RTO.Max; RTO.Alpha; + RTO.Beta. Only the initial, minimum and maximum RTO are also + described as configurable in the SCTP sockets API extensions + [RFC6458]. - Set DSCP value: Section 8.1.12 of [RFC6458] explains how to set the - DSCP value per peer address of an association. + Set DSCP value: The DSCP value can be set per peer address of an + association (section 8.1.12 of [RFC6458]). - Set IPv6 flow label: Section 8.1.12 of [RFC6458] explains how to set - the flow label field per peer address of an association. + Set IPv6 flow label: The flow label field can be set per peer + address of an association (section 8.1.12 of [RFC6458]). Set Partial Delivery Point: This allows to specify the size of a message where partial delivery will be invoked. Setting this to a lower value will cause partial deliveries to happen more often [RFC6458]. COMMUNICATION UP notification: When a lost communication to an endpoint is restored or when SCTP becomes ready to send or receive user messages, this notification informs the application process about the affected association, the type of event that has @@ -702,63 +713,61 @@ RESTART notification: When SCTP has detected that the peer has restarted, this notification is passed to the upper layer [RFC6458]. DATA ARRIVE notification: When a message is ready to be retrieved via the Receive primitive, the application is informed by this notification. SEND FAILURE notification / Receive Unsent Message / Receive - Unacknowledged Message: When a message cannot be delivered via an - association, the sender can be informed about it and learn whether - the message has just not been acknowledged or (e.g. in case of - lifetime expiry) if it has not even been sent. This can also - inform the sender that a part of the message has been successfully - delivered. + Unacknowledged Message: + When a message cannot be delivered via an association, the sender + can be informed about it and learn whether the message has just + not been acknowledged or (e.g. in case of lifetime expiry) if it + has not even been sent. This can also inform the sender that a + part of the message has been successfully delivered. NETWORK STATUS CHANGE notification: The NETWORK STATUS CHANGE notification informs the application about a socket becoming active/inactive [RFC4960] or "Potentially Failed" [RFC7829]. COMMUNICATION LOST notification: When SCTP loses communication to an endpoint (e.g. via Heartbeats or excessive retransmission) or detects an abort, this notification informs the application process of the affected association and the type of event (failure OR termination in response to a shutdown or abort request). SHUTDOWN COMPLETE notification: When SCTP completes the shutdown procedures, this notification is passed to the upper layer, informing it about the affected assocation. AUTHENTICATION notification: When SCTP wants to notify the upper - layer regarding the key management related to the extension - defined in [RFC4895], this notification is passed to the upper - layer. + layer regarding the key management related to authenticated chunks + [RFC4895], this notification is passed to the upper layer. ADAPTATION LAYER INDICATION notification: When SCTP completes the association setup and the peer provided an adaptation layer - indication, this is passed to the upper layer. This extension is - defined in [RFC5061] and [RFC6458]. + indication, this is passed to the upper layer [RFC5061], + [RFC6458]. STREAM RESET notification: When SCTP completes the procedure for - resetting streams as specified in [RFC6525], this notification is - passed to the upper layer, informing it about the result. + resetting streams [RFC6525], this notification is passed to the + upper layer, informing it about the result. ASSOCIATION RESET notification: When SCTP completes the association - reset procedure as specified in [RFC6525], this notification is - passed to the upper layer, informing it about the result. + reset procedure [RFC6525], this notification is passed to the + upper layer, informing it about the result. STREAM CHANGE notification: When SCTP completes the procedure used - to increase the number of streams as specified in [RFC6525], this - notification is passed to the upper layer, informing it about the - result. + to increase the number of streams [RFC6525], this notification is + passed to the upper layer, informing it about the result. SENDER DRY notification: When SCTP has no more user data to send or retransmit on a particular association, this notification is passed to the upper layer [RFC6458]. PARTIAL DELIVERY ABORTED notification: When a receiver has begun to receive parts of a user message but the delivery of this message is then aborted, this notification is passed to the upper layer (section 6.1.7 of [RFC6458]). @@ -770,74 +779,100 @@ optionally be passed to the application (e.g., identification to retrieve unsent and unacknowledged data). SCTP "can invoke" a COMMUNICATION ERROR notification and "may send" a RESTART notification, making these two notifications optional to implement. The list provided under 'Status' includes "etc", indicating that more information could be provided. The primitive 'Get SRTT Report' returns information that is included in the information that 'Status' provides and is therefore not discussed. The 'Destroy SCTP Instance' API function was excluded: it erases the SCTP instance that was created by 'Initialize', but is not a Primitive as defined in this - document because it does not relate to a Transport Feature. The - SHUTDOWN EVENT described in Section 6.1 of [RFC6458] informs an - application that the peer has sent a SHUTDOWN, and hence no further - data should be sent on this socket. However, if an application would - try to send data on the socket, it would get an error message anyway; - thus, this event is classified as "just affecting the application + document because it does not relate to a transport feature. The + SHUTDOWN EVENT informs an application that the peer has sent a + SHUTDOWN, and hence no further data should be sent on this socket + (section 6.1 of [RFC6458]). However, if an application would try to + send data on the socket, it would get an error message anyway; thus, + this event is classified as "just affecting the application programming style, not how the underlying protocol operates" and not included here. 3.4. Primitives Provided by UDP and UDP-Lite - The primitives provided by UDP and UDP-Lite are described in [FJ16]. + The initial UDP specification [RFC0768] states: "This User Datagram + Protocol (UDP) is defined to make available a datagram mode of + packet-switched computer communication in the environment of an + interconnected set of computer networks." It "provides a procedure + for application programs to send messages to other programs with a + minimum of protocol mechanism (..)". + + The User Interface section of RFC768 states that the user interface + to an application should be able to create receive, source and + destination ports and addresses, and provide operations to receive + data based on ports with an indication of source port and address. + Operations should be provided that allow datagrams be sent specifying + the source and destination ports and addresses to be sent. + + UDP offers only a basic transport interface. UDP datagrams may be + directly sent and received, without exchanging messages between the + endpoints to setup a connection (i.e., no handshake is performed by + the transport protocol prior to communication). Neither UDP nor UDP- + Lite provide congestion control, retransmission, nor do they have + support to optimise fragmentation and other transport functions. + This means that applications using UDP need to provide additional + functions on top of the UDP transport API [RFC8085]. Guidance on the + use of the services provided by UDP is provided in the UDP Guidelines + [RFC8085]. + + The set of pass 1 primitives for UDP and UDP-Lite is documented in + [FJ16]. 3.5. The service of LEDBAT The service of the Low Extra Delay Background Transport (LEDBAT) - congestion control mechanism is described in the abstract of - [RFC6817] as follows: "LEDBAT is designed for use by background bulk- - transfer applications to be no more aggressive than standard TCP - congestion control (as specified in RFC 5681) and to yield in the - presence of competing flows, thus limiting interference with the - network performance of competing flows." + congestion control mechanism is described as follows: "LEDBAT is + designed for use by background bulk-transfer applications to be no + more aggressive than standard TCP congestion control (as specified in + RFC 5681) and to yield in the presence of competing flows, thus + limiting interference with the network performance of competing + flows" [RFC6817]. LEDBAT does not have any primitives, as LEDBAT is not a transport - protocol. [RFC6817] states: "LEDBAT can be used as part of a - transport protocol or as part of an application, as long as the data - transmission mechanisms are capable of carrying timestamps and - acknowledging data frequently. LEDBAT can be used with TCP, Stream - Control Transmission Protocol (SCTP), and Datagram Congestion Control - Protocol (DCCP), with appropriate extensions where necessary; and it - can be used with proprietary application protocols, such as those - built on top of UDP for peer-to- peer (P2P) applications." At the - time of writing, the appropriate extensions for TCP, SCTP or DCCP do - not exist. + protocol. According to its specification [RFC6817], "LEDBAT can be + used as part of a transport protocol or as part of an application, as + long as the data transmission mechanisms are capable of carrying + timestamps and acknowledging data frequently. LEDBAT can be used + with TCP, Stream Control Transmission Protocol (SCTP), and Datagram + Congestion Control Protocol (DCCP), with appropriate extensions where + necessary; and it can be used with proprietary application protocols, + such as those built on top of UDP for peer-to- peer (P2P) + applications." At the time of writing, the appropriate extensions + for TCP, SCTP or DCCP do not exist. A numer of configurable parameters exist in the LEDBAT specification: TARGET, which is the queuing delay target at which LEDBAT tries to operate, must be set to 100ms or less. ALLOWED_INCREASE (should be 1, must be greater than 0) limits the speed at which LEDBAT increases its rate. GAIN, which MUST be set to 1 or less to avoid a faster ramp-up than TCP Reno, determines how quickly the sender responds to changes in queueing delay. Implementations may divide GAIN into two parameters, one for increase and a possibly larger one for decrease. We call these parameters GAIN_INC and GAIN_DEC here. BASE_HISTORY is the size of the list of measured base delays, and SHOULD be 10. This list can be filtered using a FILTER() function which is not - prescribed in [RFC6817], yielding a list of size CURRENT_FILTER. The + prescribed [RFC6817], yielding a list of size CURRENT_FILTER. The initial and minimum congestion windows, INIT_CWND and MIN_CWND, should both be 2. Regarding which of these parameters should be under control of an application, the possible range goes from exposing nothing on the one - hand, to considering everything that is not fully prescribed with a - MUST in [RFC6817] as a parameter on the other hand. Function + hand, to considering everything that is not prescribed with a MUST in + the specification as a parameter on the other hand. Function implementations are not provided as a parameter to any of the transport protocols discussed here, and hence we do not regard the FILTER() function as a parameter. However, to avoid unnecessarily limiting future implementations, we consider all other parameters above as tunable parameters that should be exposed. 4. Pass 2 This pass categorizes the primitives from pass 1 based on whether they relate to a connection or to data transmission. Primitives are @@ -852,50 +887,50 @@ concept and use it to refer to, e.g., TCP connections (identifiable by a unique pair of IP addresses and TCP port numbers), SCTP associations (identifiable by multiple IP address and port number pairs), as well UDP and UDP-Lite connections (identifiable by a unique socket pair). Some minor details are omitted for the sake of generalization -- e.g., SCTP's 'close' [RFC4960] returns success or failure, and lets the application control whether further receive or send operations or both are disabled [RFC6458]. This is not described in the same way - for TCP in [RFC0793], but these details play no significant role for - the primitives provided by either TCP or SCTP (for the sake of being + for TCP [RFC0793], but these details play no significant role for the + primitives provided by either TCP or SCTP (for the sake of being generic, it could be assumed that both receive and send operations are disabled in both cases). The TCP 'send' and 'receive' primitives include usage of an "URGENT" mechanism. This mechanism is required to implement the "synch signal" used by telnet [RFC0854], but SHOULD NOT be used by new applications [RFC6093]. Because pass 2 is meant as a basis for the creation of future systems, the "URGENT" mechanism is excluded. This also concerns the notification "Urgent pointer advance" in the - ERROR_REPORT described in Section 4.2.4.1 of [RFC1122]. + ERROR_REPORT (section 4.2.4.1 of [RFC1122]). Since LEDBAT is a congestion control mechanism and not a protocol, it is not currently defined when to enable / disable or configure the mechanism. For instance, it could be a one-time choice upon connection establishment or when listening for incoming connections, in which case it should be categorized under CONNECTION.ESTABLISHMENT or CONNECTION.AVAILABILITY, respectively. To avoid unnecessarily limiting future implementations, it was decided to place it under - CONNECTION.MAINTENANCE, with all parameters that are described in - [RFC6817] made configurable. + CONNECTION.MAINTENANCE, with all parameters that are described in the + specification [RFC6817] made configurable. 4.1. CONNECTION Related Primitives ESTABLISHMENT: Active creation of a connection from one transport endpoint to one or more transport endpoints. Interfaces to UDP and UDP-Lite allow both connection-oriented and - connection-less usage of the API . [RFC8085] + connection-less usage of the API [RFC8085]. o CONNECT.TCP: Pass 1 primitive / event: 'open' (active) or 'open' (passive) with socket, followed by 'send' Parameters: 1 local IP address (optional); 1 destination transport address (for active open; else the socket and the local IP address of the succeeding incoming connection request will be maintained); timeout (optional); options (optional); MKT configuration (optional); user message (optional) Comments: If the local IP address is not provided, a default @@ -1126,23 +1163,21 @@ o STATUS.MPTCP: Pass 1 primitive / event: not specified Returns: list of pairs of tuples of IP address and TCP port number of each subflow. The first of the pair is the local IP and port number, while the second is the remote IP and port number. o SET_DSCP.TCP: Pass 1 primitive / event: not specified Parameters: DSCP value Comments: this allows an application to change the DSCP value for - outgoing segments. For TCP this was originally specified for the - TOS field [RFC1122], which is here interpreted to refer to the - DSField [RFC3260]. + outgoing segments. o SET_DSCP.SCTP: Pass 1 primitive / event: 'Set DSCP value' Parameters: DSCP value Comments: this allows an application to change the DSCP value for outgoing packets on a path. o SET_DSCP.UDP(-Lite): Pass 1 primitive / event: 'SET_DSCP' Parameter: DSCP value @@ -1153,39 +1188,39 @@ o ERROR.TCP: Pass 1 primitive / event: 'ERROR_REPORT' Returns: reason (encoding not specified); subreason (encoding not specified) Comments: soft errors that can be ignored without harm by many applications; an application should be able to disable these notifications. The reported conditions include at least: ICMP error message arrived; Excessive Retransmissions. o ERROR.UDP(-Lite): - Pass 1 primitive / event: 'ERROR_REPORT'. + Pass 1 primitive / event: 'ERROR_REPORT' Returns: Error report Comments: This returns soft errors that may be ignored without harm by many applications; An application must connect to be able receive these notifications. o SET_AUTH.TCP: - Pass 1 primitive / event: 'send' + Pass 1 primitive / event: not specified Parameters: current_key, rnext_key Comments: current_key and rnext_key are the preferred outgoing MKT and the preferred incoming MKT, respectively, for a segment that - is sent on an active option. + is sent on the connection. o SET_AUTH.SCTP: Pass 1 primitive / event: 'Set / Get Authentication Parameters' Parameters: key_id, key, hmac_id o GET_AUTH.TCP: - Pass 1 primitive / event: 'receive' + Pass 1 primitive / event: not specified Parameters: current_key, rnext_key Comments: current_key and rnext_key are the preferred outgoing MKT and the preferred incoming MKT, respectively, that were carried on a recently received segment. o GET_AUTH.SCTP: Pass 1 primitive / event: 'Set / Get Authentication Parameters' Parameters: key_id, chunk_list o RESET_STREAM.SCTP: @@ -1193,21 +1228,21 @@ Parameters: sid, direction o RESET_STREAM-EVENT.SCTP: Pass 1 primitive / event: 'STREAM RESET notification' Parameters: information about the result of RESET_STREAM.SCTP. Comments: This is issued when the procedure for resetting streams has completed. o RESET_ASSOC.SCTP: Pass 1 primitive / event: 'Add / Reset Streams, Reset Association' - Parameters: information related to the extension defined in + Parameters: information related to the extension, defined in [RFC3260]. o RESET_ASSOC-EVENT.SCTP: Pass 1 primitive / event: 'ASSOCIATION RESET notification' Parameters: information about the result of RESET_ASSOC.SCTP. Comments: This is issued when the procedure for resetting an association has completed. o ADD_STREAM.SCTP: Pass 1 primitive / event: 'Add / Reset Streams, Reset Association' @@ -1296,59 +1331,72 @@ Parameters: max burst value Comments: not all implementations allow values above the default of 4. o SET_PARTIAL_DELIVERY_POINT.SCTP: Pass 1 primitive / event: 'Set Partial Delivery Point' Parameters: partial delivery point (integer) Comments: this parameter must be smaller or equal to the socket receive buffer size. - o CHECKSUM.UDP: - Pass 1 primitive / event: 'DISABLE_CHECKSUM'. - Parameters: 0 when no checksum is used at sender, 1 for checksum + o SET_CHECKSUM_ENABLED.UDP: + Pass 1 primitive / event: 'CHECKSUM_ENABLED'. + Parameters: 0 when zero checksum is used at sender, 1 for checksum at sender (default) - o CHECKSUM_REQUIRED.UDP: + o SET_CHECKSUM_REQUIRED.UDP: Pass 1 primitive / event: 'REQUIRE_CHECKSUM'. - Parameter: 0 when checksum is required at receiver, 1 to allow - zero checksum at receiver (default) + Parameter: 0 to allow zero checksum, 1 when a non-zero checksum is + required (default) at receiver o SET_CHECKSUM_COVERAGE.UDP-Lite: Pass 1 primitive / event: 'SET_CHECKSUM_COVERAGE' Parameters: Coverage length at sender (default maximum coverage) o SET_MIN_CHECKSUM_COVERAGE.UDP-Lite: Pass 1 primitive / event: 'SET_MIN_COVERAGE'. Parameter: Coverage length at receiver (default minimum coverage) o SET_DF.UDP(-Lite): Pass 1 primitive event: 'SET_DF'. - Parameter: 0 when DF is not set (default), 1 when DF is set + Parameter: 0 when DF is not set (default) in the IPv4 header, 1 + when DF is set + + o GET_MMS_S.UDP(-Lite): + Pass 1 primitive event: 'GET_MMS_S'. + Comments: this retrieves the maximum transport-message size that + may be sent using a non-fragmented IP packet from the configured + interface. + + o GET_MMS_R.UDP(-Lite): + Pass 1 primitive event: 'GET_MMS_R'. + Comments: this retrieves the maximum transport-message size that + may be received from the configured interface. o SET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS): Pass 1 primitive / event: 'SET_TTL' and 'SET_IPV6_UNICAST_HOPS' Parameters: IPv4 TTL value or IPv6 Hop Count value Comments: This allows an application to change the IPv4 TTL of IPv6 Hop count value for outgoing UDP(-Lite) datagrams. o GET_TTL.UDP(-Lite) (IPV6_UNICAST_HOPS): Pass 1 primitive / event: 'GET_TTL' and 'GET_IPV6_UNICAST_HOPS' Returns: IPv4 TTL value or IPv6 Hop Count value Comments: This allows an application to read the the IPv4 TTL of IPv6 Hop count value from a received UDP(-Lite) datagram. o SET_ECN.UDP(-Lite): Pass 1 primitive / event: 'SET_ECN' Parameters: ECN value Comments: This allows a UDP(-Lite) application to set the ECN - codepoint field for outgoing UDP(-Lite) datagrams. + codepoint field for outgoing UDP(-Lite) datagrams. Defaults to + sending '00'. o GET_ECN.UDP(-Lite): Pass 1 primitive / event: 'GET_ECN' Parameters: ECN value Comments: This allows a UDP(-Lite) application to read the ECN codepoint field from a received UDP(-Lite) datagram. o SET_IP_OPTIONS.UDP(-Lite): Pass 1 primitive / event: 'SET_IP_OPTIONS' Parameters: options @@ -1391,34 +1439,34 @@ o ABORT.SCTP: Pass 1 primitive / event: 'abort' Parameters: abort reason to be given to the peer (optional) Comments: this terminates a connection without delivering remaining data and sends an error message to the other side. o ABORT.UDP(-Lite): Pass 1 primitive event: 'CLOSE' Comments: this terminates a connection without delivering remaining data. No further UDP(-Lite) datagrams are sent/received - on this connection. + for this transport service instance. o TIMEOUT.TCP: Pass 1 primitive / event: 'USER TIMEOUT' event Comments: the application is informed that the connection is aborted. This event is executed on expiration of the timeout set in CONNECTION.ESTABLISHMENT.CONNECT.TCP (possibly adjusted in CONNECTION.MAINTENANCE.CHANGE_TIMEOUT.TCP). o TIMEOUT.SCTP: Pass 1 primitive / event: 'COMMUNICATION LOST' event Comments: the application is informed that the connection is aborted. this event is executed on expiration of the timeout that - should be enabled by default (see beginning of section 8.3 in + should be enabled by default (see the beginning of section 8.3 in [RFC4960]) and was possibly adjusted in CONNECTION.MAINTENANCE.CHANGE_TIMEOOUT.SCTP. o ABORT-EVENT.TCP: Pass 1 primitive / event: not specified. o ABORT-EVENT.SCTP: Pass 1 primitive / event: 'COMMUNICATION LOST' event Returns: abort reason from the peer (if available) Comments: the application is informed that the other side has @@ -1538,41 +1587,41 @@ Comments: This informs the application that the stack has no more user data to send. o PARTIAL_DELIVERY_ABORTED-EVENT.SCTP: Pass 1 primitive / event: 'PARTIAL DELIVERY ABORTED' notification Comments: This informs the receiver of a partial message that the further delivery of the message has been aborted. 5. Pass 3 - This section presents the superset of all Transport Features in all + This section presents the superset of all transport features in all protocols that were discussed in the preceding sections, based on the list of primitives in pass 2 but also on text in pass 1 to include - features that can be configured in one protocol and are static - properties in another (congestion control, for example). Again, some - minor details are omitted for the sake of generalization -- e.g., TCP - may provide various different IP options, but only source route is - mandatory to implement, and this detail is not visible in the Pass 3 - feature "Specify IP Options". + transport features that can be configured in one protocol and are + static properties in another (congestion control, for example). + Again, some minor details are omitted for the sake of generalization + -- e.g., TCP may provide various different IP options, but only + source route is mandatory to implement, and this detail is not + visible in the Pass 3 transport feature "Specify IP Options". 5.1. CONNECTION Related Transport Features ESTABLISHMENT: Active creation of a connection from one transport endpoint to one or more transport endpoints. o Connect Protocols: TCP, SCTP, UDP(-Lite) o Specify which IP Options must always be used - Protocols: TCP + Protocols: TCP, UDP(-Lite) o Request multiple streams Protocols: SCTP o Limit the number of inbound streams Protocols: SCTP o Specify number of attempts and/or timeout for the first establishment message Protocols: TCP, SCTP @@ -1606,33 +1655,33 @@ o Enable UDP encapsulation with a specified remote UDP port number Protocols: SCTP AVAILABILITY: Preparing to receive incoming connection requests. o Listen, 1 specified local interface Protocols: TCP, SCTP, UDP(-Lite) o Listen, N specified local interfaces - Protocols: SCTP, UDP(-Lite) + Protocols: SCTP o Listen, all local interfaces Protocols: TCP, SCTP, UDP(-Lite) o Obtain requested number of streams Protocols: SCTP o Limit the number of inbound streams Protocols: SCTP o Specify which IP Options must always be used - Protocols: TCP + Protocols: TCP, UDP(-Lite) o Disable MPTCP Protocols: MPTCP o Configure authentication Protocols: TCP, SCTP Comments: With TCP, this allows to configure Master Key Tuples (MKTs). In SCTP, this allows to specify which chunk types must always be authenticated. DATA, ACK etc. are different 'chunks' in SCTP; one or more chunks may be included in a single packet. @@ -1765,20 +1814,28 @@ o Specify checksum coverage used by the sender Protocols: UDP-Lite o Specify minimum checksum coverage required by receiver Protocols: UDP-Lite o Specify DF field Protocols: UDP(-Lite) + o Get max. transport-message size that may be sent using a non- + fragmented IP packet from the configured interface + Protocols: UDP(-Lite) + + o Get max. transport-message size that may be received from the + configured interface + Protocols: UDP(-Lite) + o Specify TTL/Hop count field Protocols: UDP(-Lite) o Obtain TTL/Hop count field Protocols: UDP(-Lite) o Specify ECN field Protocols: UDP(-Lite) o Obtain ECN field @@ -1816,34 +1873,34 @@ Protocols: UDP(-Lite) o Timeout event when data could not be delivered for too long Protocols: TCP, SCTP Comments: the timeout is configured with CONNECTION.MAINTENANCE "Change timeout for aborting connection (using retransmit limit or time value)". 5.2. DATA Transfer Related Transport Features - All features in this section refer to an existing connection, i.e. a - connection that was either established or made available for - receiving data. Note that TCP allows to transfer data (a single - optional user message, possibly arriving multiple times) before the - connection is fully established. Reliable data transfer entails - delay -- e.g. for the sender to wait until it can transmit data, or - due to retransmission in case of packet loss. + All transport features in this section refer to an existing + connection, i.e. a connection that was either established or made + available for receiving data. Note that TCP allows to transfer data + (a single optional user message, possibly arriving multiple times) + before the connection is fully established. Reliable data transfer + entails delay -- e.g. for the sender to wait until it can transmit + data, or due to retransmission in case of packet loss. 5.2.1. Sending Data - All features in this section are provided by DATA.SEND from pass 2. - DATA.SEND is given a data block from the application, which we here - call a "message" if the beginning and end of the data block can be - identified at the receiver, and "data" otherwise. + All transport features in this section are provided by DATA.SEND from + pass 2. DATA.SEND is given a data block from the application, which + we here call a "message" if the beginning and end of the data block + can be identified at the receiver, and "data" otherwise. o Reliably transfer data, with congestion control Protocols: TCP o Reliably transfer a message, with congestion control Protocols: SCTP o Unreliably transfer a message, with congestion control Protocols: SCTP @@ -1871,24 +1928,25 @@ Protocols: SCTP o Specifying a key id to be used to authenticate a message Protocols: SCTP o Request not to delay the acknowledgement (SACK) of a message Protocols: SCTP 5.2.2. Receiving Data - All features in this section are provided by DATA.RECEIVE from pass - 2. DATA.RECEIVE fills a buffer provided by the application, with - what we here call a "message" if the beginning and end of the data - block can be identified at the receiver, and "data" otherwise. + All transport features in this section are provided by DATA.RECEIVE + from pass 2. DATA.RECEIVE fills a buffer provided by the + application, with what we here call a "message" if the beginning and + end of the data block can be identified at the receiver, and "data" + otherwise. o Receive data (with no message delineation) Protocols: TCP o Receive a message Protocols: SCTP, UDP(-Lite) o Choice of stream to receive from Protocols: SCTP @@ -1921,106 +1979,113 @@ been aborted Protocols: SCTP 6. Acknowledgements The authors would like to thank (in alphabetical order) Bob Briscoe, David Hayes, Karen Nielsen, Joe Touch and Brian Trammell for providing valuable feedback on this document. We especially thank Christoph Paasch for providing input related to Multipath TCP, and Gorry Fairhurst and Tom Jones for providing input related to UDP(- - Lite), via [FJ16]. This work has received funding from the European - Union's Horizon 2020 research and innovation programme under grant - agreement No. 644334 (NEAT). The views expressed are solely those of - the author(s). + Lite). This work has received funding from the European Union's + Horizon 2020 research and innovation programme under grant agreement + No. 644334 (NEAT). The views expressed are solely those of the + author(s). 7. IANA Considerations XX RFC ED - PLEASE REMOVE THIS SECTION XXX This memo includes no request to IANA. 8. Security Considerations Authentication, confidentiality protection, and integrity protection - are identified as Transport Features by [RFC8095]. As currently - deployed in the Internet, these features are generally provided by a - protocol or layer on top of the transport protocol; no current full- - featured standards-track transport protocol provides these features - on its own. Therefore, these features are not considered in this - document, with the exception of native authentication capabilities of - TCP and SCTP for which the security considerations in [RFC5925] and - [RFC4895] apply. + are identified as transport features [RFC8095]. As currently + deployed in the Internet, these transport features are generally + provided by a protocol or layer on top of the transport protocol; no + current full-featured standards-track transport protocol provides + these transport features on its own. Therefore, these transport + features are not considered in this document, with the exception of + native authentication capabilities of TCP and SCTP for which the + security considerations in [RFC5925] and [RFC4895] apply. + + Security considerations for the use of UDP and UDP-Lite are provided + in the referenced RFCs. Security guidance for application usage is + provided in the UDP-Guidelines [RFC8085]. 9. References 9.1. Normative References [FJ16] Fairhurst, G. and T. Jones, "Features of the User Datagram Protocol (UDP) and Lightweight UDP (UDP-Lite) Transport - Protocols", draft-ietf-taps-transports-usage-udp-00 (work - in progress), November 2016. + Protocols", Internet-draft draft-ietf-taps-transports- + usage-udp-02, May 2017. [I-D.ietf-tsvwg-sctp-ndata] Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "Stream Schedulers and User Message Interleaving for the - Stream Control Transmission Protocol", - draft-ietf-tsvwg-sctp-ndata-08 (work in progress), - October 2016. + Stream Control Transmission Protocol", draft-ietf-tsvwg- + sctp-ndata-08 (work in progress), October 2016. + + [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, + DOI 10.17487/RFC0768, August 1980, + . [RFC0793] 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, + Communication Layers", STD 3, RFC 1122, + DOI 10.17487/RFC1122, October 1989, . [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, + Partial Reliability Extension", RFC 3758, + DOI 10.17487/RFC3758, May 2004, . [RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla, "Authenticated Chunks for the Stream Control Transmission - Protocol (SCTP)", RFC 4895, DOI 10.17487/RFC4895, - August 2007, . + Protocol (SCTP)", RFC 4895, DOI 10.17487/RFC4895, August + 2007, . [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", RFC 4960, DOI 10.17487/RFC4960, September 2007, . [RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M. Kozuka, "Stream Control Transmission Protocol (SCTP) - Dynamic Address Reconfiguration", RFC 5061, DOI 10.17487/ - RFC5061, September 2007, + Dynamic Address Reconfiguration", RFC 5061, + DOI 10.17487/RFC5061, September 2007, . [RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option", RFC 5482, DOI 10.17487/RFC5482, March 2009, . [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, DOI 10.17487/RFC5925, June 2010, . [RFC6182] Ford, A., Raiciu, C., Handley, M., Barre, S., and J. Iyengar, "Architectural Guidelines for Multipath TCP Development", RFC 6182, DOI 10.17487/RFC6182, March 2011, . [RFC6458] Stewart, R., Tuexen, M., Poon, K., Lei, P., and V. Yasevich, "Sockets API Extensions for the Stream Control - Transmission Protocol (SCTP)", RFC 6458, DOI 10.17487/ - RFC6458, December 2011, + Transmission Protocol (SCTP)", RFC 6458, + DOI 10.17487/RFC6458, December 2011, . [RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control Transmission Protocol (SCTP) Stream Reconfiguration", RFC 6525, DOI 10.17487/RFC6525, February 2012, . [RFC6817] Shalunov, S., Hazel, G., Iyengar, J., and M. Kuehlewind, "Low Extra Delay Background Transport (LEDBAT)", RFC 6817, DOI 10.17487/RFC6817, December 2012, @@ -2030,22 +2095,22 @@ "TCP Extensions for Multipath Operation with Multiple Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013, . [RFC6897] Scharf, M. and A. Ford, "Multipath TCP (MPTCP) Application Interface Considerations", RFC 6897, DOI 10.17487/RFC6897, March 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, + to End-Host Communication", RFC 6951, + DOI 10.17487/RFC6951, May 2013, . [RFC7053] Tuexen, M., Ruengeler, I., and R. Stewart, "SACK- IMMEDIATELY Extension for the Stream Control Transmission Protocol", RFC 7053, DOI 10.17487/RFC7053, November 2013, . [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, . @@ -2063,90 +2128,96 @@ . [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, March 2017, . 9.2. Informative References [I-D.draft-gjessing-taps-minset] Gjessing, S. and M. Welzl, "A Minimal Set of Transport - Services for TAPS Systems", draft-gjessing-taps-minset-04 - (work in progress), March 2017. + Services for TAPS Systems", Internet-draft draft-gjessing- + taps-minset-04, March 2017. [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol - Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, - May 1983, . + Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May + 1983, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ - RFC2119, March 1997, + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, . - [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, - . + [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, + . + + [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, + . [RFC3260] Grossman, D., "New Terminology and Clarifications for Diffserv", RFC 3260, DOI 10.17487/RFC3260, April 2002, . [RFC5461] Gont, F., "TCP's Reaction to Soft Errors", RFC 5461, DOI 10.17487/RFC5461, February 2009, . [RFC6093] Gont, F. and A. Yourtchenko, "On the Implementation of the TCP Urgent Mechanism", RFC 6093, DOI 10.17487/RFC6093, January 2011, . [RFC7414] Duke, M., Braden, R., Eddy, W., Blanton, E., and A. Zimmermann, "A Roadmap for Transmission Control Protocol - (TCP) Specification Documents", RFC 7414, DOI 10.17487/ - RFC7414, February 2015, + (TCP) Specification Documents", RFC 7414, + DOI 10.17487/RFC7414, February 2015, . [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services (Diffserv) and Real-Time Communication", RFC 7657, DOI 10.17487/RFC7657, November 2015, . [RFC8095] Fairhurst, G., Ed., Trammell, B., Ed., and M. Kuehlewind, Ed., "Services Provided by IETF Transport Protocols and - Congestion Control Mechanisms", RFC 8095, DOI 10.17487/ - RFC8095, March 2017, + Congestion Control Mechanisms", RFC 8095, + DOI 10.17487/RFC8095, March 2017, . Appendix A. Overview of RFCs used as input for pass 1 TCP: [RFC0793], [RFC1122], [RFC5482], [RFC5925], [RFC7413] MPTCP: [RFC6182], [RFC6824], [RFC6897] SCTP: RFCs without a socket API specification: [RFC3758], [RFC4895], [RFC4960], [RFC5061]. RFCs that include a socket API specification: [RFC6458], [RFC6525], [RFC6951], [RFC7053], [RFC7496] [RFC7829]. UDP(-Lite): See [FJ16] LEDBAT: [RFC6817]. Appendix B. How this document was developed This section gives an overview of the method that was used to develop this document. It was given to contributors for guidance, and it can be helpful for future updates or extensions. - This document is only concerned with Transport Features that are + This document is only concerned with transport features that are explicitly exposed to applications via primitives. It also strictly - follows RFC text: if a feature is truly relevant for an application, - the RFCs should say so, and they should describe how to use and - configure it. Thus, the approach followed for developing this - document was to identify the right RFCs, then analyze and process - their text. + follows RFC text: if a transport feature is truly relevant for an + application, the RFCs should say so, and they should describe how to + use and configure it. Thus, the approach followed for developing + this document was to identify the right RFCs, then analyze and + process their text. Primitives that MAY be implemented by a transport protocol were excluded. To be included, the minimum requirement level for a primitive to be implemented by a protocol was SHOULD. Where [RFC2119]-style requirements levels are not used, primitives were excluded when they are described in conjunction with statements like, e.g.: "some implementations also provide" or "an implementation may also". Excluded primitives or parameters were briefly described in a dedicated subsection. @@ -2191,26 +2262,26 @@ Parameters: Returns: Comments: The entries "Parameters", "Returns" and "Comments" were skipped when a primitive had no parameters, no described return value or no comments seemed necessary, respectively. Optional parameters are followed by "(optional)". When a default value is known, this was also provided. - Pass 3: the main point of this pass is to identify transport protocol - features that are the result of static properties of protocols, for - which all protocols have to be listed together; this is then the - final list of all available Transport Features. This list was - primarily based on text from pass 2, with additional input from pass - 1 (but no external sources). + Pass 3: the main point of this pass is to identify transport features + that are the result of static properties of protocols, for which all + protocols have to be listed together; this is then the final list of + all available transport features. This list was primarily based on + text from pass 2, with additional input from pass 1 (but no external + sources). Appendix C. Revision information XXX RFC-Ed please remove this section prior to publication. -00 (from draft-welzl-taps-transports): this now covers TCP based on all TCP RFCs (this means: if you know of something in any TCP RFC that you think should be addressed, please speak up!) as well as SCTP, exclusively based on [RFC4960]. We decided to also incorporate [RFC6458] for SCTP, but this hasn't happened yet. Terminology made @@ -2223,54 +2294,59 @@ -02: included UDP, UDP-Lite, and all extensions of SCTPs. This includes fixing the [RFC6458] omission from -00. -03: wrote security considerations. The "how to contribute" section was updated to reflect how the document WAS created, not how it SHOULD BE created; it also no longer wrongly says that Experimental RFCs are excluded. Included LEDBAT. Changed abstract and intro to reflect which protocols/mechanisms are covered (TCP, MPTCP, SCTP, UDP, UDP-Lite, LEDBAT) instead of talking about "transport - protocols". Interleaving and stream scheduling added - (draft-ietf-tsvwg-sctp-ndata). TFO added. "Set protocol parameters" - in SCTP replaced with per-parameter (or parameter group) primitives. - More primitives added, mostly previously overlooked ones from - [RFC6458]. Updated terminology (s/transport service feature/ - transport feature) in line with an update of [RFC8095]. Made - sequence of transport features / primitives more logical. Combined - MPTCP's add/rem subflow with SCTP's add/remove local address. + protocols". Interleaving and stream scheduling added (draft-ietf- + tsvwg-sctp-ndata). TFO added. "Set protocol parameters" in SCTP + replaced with per-parameter (or parameter group) primitives. More + primitives added, mostly previously overlooked ones from [RFC6458]. + Updated terminology (s/transport service feature/transport feature) + in line with an update of [RFC8095]. Made sequence of transport + features / primitives more logical. Combined MPTCP's add/rem subflow + with SCTP's add/remove local address. -04: changed UDP's close into an ABORT (to better fit with the primitives of TCP and SCTP), and incorporated the corresponding transport feature in step 3 (this addresses a comment from Gorry Fairhurst). Added TCP Authentication (RFC 5925, section 7.1). Changed TFO from looking like a primitive in pass 1 to be a part of 'open'. Changed description of SCTP authentication in pass 3 to encompass both TCP and SCTP. Added citations of [RFC8095] and minset + [I-D.draft-gjessing-taps-minset] to the intro, to give the context of this document. + -05: minor fix to TCP authentication (comment from Joe Touch), + several fixes from Gorry Fairhurst and Tom Jones. Language fixes; + updated to align with latest taps-transport-usage-udp ID. + Authors' Addresses Michael Welzl University of Oslo PO Box 1080 Blindern - Oslo, N-0316 + Oslo N-0316 Norway Email: michawe@ifi.uio.no Michael Tuexen Muenster University of Applied Sciences Stegerwaldstrasse 39 Steinfurt 48565 Germany Email: tuexen@fh-muenster.de Naeem Khademi University of Oslo PO Box 1080 Blindern - Oslo, N-0316 + Oslo N-0316 Norway Email: naeemk@ifi.uio.no