TAPS S. Gjessing
Internet-Draft M. Welzl
Intended status: Informational University of Oslo
Expires: December 24, 2015 June 22, 2015
A Minimal Set of Transport Services for TAPS Systems
draft-gjessing-taps-minset-00
Abstract
This draft will eventually recommend a minimal set of IETF Transport
Services offered by end systems supporting TAPS, and give guidance on
choosing among the available mechanisms and protocols. As a starting
point for discussion, it currently only gives an overview of some
ways to categorize the set of transport services in the first TAPS
document (version 4: draft-ietf-taps-transports-04), assuming that
the eventual minimal set of transport services will be based on a
similar form of categorization.
Status of this Memo
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This Internet-Draft will expire on December 24, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology (as defined by draft-ietf-taps-transports-04) . . 4
3. A list of all features in the considered IETF Transport
Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Grouping of the features . . . . . . . . . . . . . . . . . . . 6
4.1. Functional vs. non-functional . . . . . . . . . . . . . . 7
4.1.1. Functional features . . . . . . . . . . . . . . . . . 7
4.1.2. Non-functional features . . . . . . . . . . . . . . . 7
4.2. Components from draft-ietf-taps-transports-04 that are
not specified or seen by the applications . . . . . . . . 9
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
An application has an intended usage and demands for transport
services, and the task of any system that implements TAPS is to offer
these services to its applications, i.e. the applications running on
top of TAPS, without binding an application to a particular transport
protocol.
The present draft is based on [TAPS1] and follows the same
terminology (also listed below). We include an "inversion" (in the
database sense) of [TAPS1], in that, based on the lists of protocol
components in [TAPS1] we list all protocol features, and for each
feature, we list the Transport Protocols that support this feature
(as a component). The resulting list is very long. If the list of
Transport Services that a TAPS system offers to applications was a
simple copy of this list, the resulting system would be very hard to
use. It is therefore necessary to minimize the number of services
that are offered. We begin this by grouping these transport
features.
The groups of features offered to applications are divided as
follows:
1. functional vs. non-functional
2. static vs. initialization vs. dynamic
3. single-sided vs. both-sided
Because QoS is out of scope of TAPS, this document assumes a "best
effort" service model [RFC5290, RFC7305]. Applications using a TAPS
system can therefore not make any assumptions about e.g. the time it
will take to send a message. There are however certain requirements
that are strictly kept by transport protocols today, and a TAPS
system.
Functional features use components that cannot be used without the
application knowing about them, or else they violate assumptions that
might cause the application to break. Components implementing non-
functional features may be used without involving the application.
For example, unordered message delivery is a functional feature: it
cannot be used without the application knowing about it because the
application's assumption could be that messages arrive in-order, and
in this case unordered delivery could cause the application to break.
Multihoming and data bundling (Nagle in TCP) are non-functional
features: if a TAPS system autonomously decides to enable or disable
them, an application will not break (but a TAPS system may be able to
communicate more efficiently if the application is in control of this
feature).
If a transport protocol offers a feature that can not be changed or
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opted out, this feature is called static in this protocol. An
application uses a static feature either because it has requested it
(and TAPS decide to fulfill this request by a protocol that has a
component that implements this feature as static), or the static
feature is offered to the application implicitly because TAPS chooses
a protocol that implements it. For example, if an application
chooses byte-stream-oriented delivery, it automatically also gets
reliable delivery.
Initialization features can be chosen when communication begins but
not adjusted later; this assumes that a TAPS system does not change
protocols during a communication session. Examples of initialization
features are flow control and congestion control.
Dynamic features are changeable during runtime. An example of a
dynamic feature is data bundling (Nagle in TCP).
Single-sided features can be provided via components that are
implemented only on the side where they applications requests the
Transport Service. An example of a single-sided feature is data
bundling (Nagle in TCP). Both-sided features can only be provided
via components that are implemented on both sides. An example is
error detection (checksum). Possibly certain features could benefit
from, but do not need to be, implemented on both sides. Since the
point of categorization is to determine the minimal set of Transport
Services that a TAPS system must provide, the essential property of
such features is that they *can* be implemented on only one side.
2. Terminology (as defined by draft-ietf-taps-transports-04)
The following terms are defined throughout this document, and in
subsequent documents produced by TAPS describing the composition and
decomposition of transport services.
Transport Service Feature: a specific end-to-end feature that a
transport service provides to its clients. Examples include
confidentiality, reliable delivery, ordered delivery, message-
versus-stream orientation, etc.
Transport Service: a set of transport service features, without an
association to any given framing protocol, which provides a
complete service to an application.
Transport Protocol: an implementation that provides one or more
different transport services using a specific framing and header
format on the wire.
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Transport Protocol Component: an implementation of a transport
service feature within a protocol.
Transport Service Instance: an arrangement of transport protocols
with a selected set of features and configuration parameters that
implements a single transport service, e.g. a protocol stack (RTP
over UDP).
Application: an entity that uses the transport layer for end-to-end
delivery data across the network (this may also be an upper layer
protocol or tunnel encapsulation).
3. A list of all features in the considered IETF Transport Protocols
[TAPS1] provides a list of known IETF transport protocols and
transport protocols frameworks. Here all features from [TAPS1] are
listed:
o unicast: TCP SCTP UDP-Lite DCCP NORM
o IPv6 multicast and anycast: UDP
o IPv4 broadcast, multicast and anycast: UDP UDP-Lite
o multicast: NORM
o unidirectional: UDP
o bidirectional: TCP
o message-oriented delivery: SCTP UDP UDP-Lite DCCP
o byte-stream-oriented delivery: TCP
o user message fragmentation and reassembly: SCTP
o IPv6 jumbograms: UDP
o connection setup with feature negotiation and application-to-port
mapping: TCP SCTP DCCP
o port multiplexing: TCP SCTP UDP UDP-Lite DCCP
o port multiplexing (UDP ports): NORM
o 2-tuple endpoints: UDP
o transport layer multihoming for resilience: SCTP
o transport layer mobility: SCTP
o non-reliable delivery: UDP-Lite DCCP
o reliable delivery: TCP NORM
o reliable or partially reliable delivery: SCTP
o drop notification: DCCP
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o ordered delivery: DCCP
o ordered delivery for each byte stream: TCP
o ordered delivery for each byte or message stream: NORM
o ordered and unordered delivery within a stream (of messages): SCTP
o unordered delivery: UDP-Lite UDP
o unordered delivery of in-memory data or file bulk content objects:
NORM
o object-oriented delivery of discrete data or file items: NORM
o partial integrity protection: UDP-Lite DCCP
o checksum optional: UDP
o error detection (checksum): TCP UDP
o error detection (UDP checksum): NORM
o strong error detection (CRC32C): SCTP
o packet erasure coding (both proactively and as part of ARQ): NORM
o flow control: TCP SCTP
o flow control (slow receiver function): DCCP
o flow control (timer-based and/or ack-based): NORM
o segmentation: TCP NORM
o stream-oriented delivery in a single stream: TCP NORM
o support for multiple concurrent streams: SCTP
o support for stream scheduling prioritization: SCTP
o data bundling (Nagle's algorithm): TCP NORM
o user message bundling: SCTP
o congestion control: TCP SCTP NORM
o no congestion control: UDP
o timestamps: DCCP
4. Grouping of the features
This section presents a grouping of the features from [TAPS1]
according to the three categories: functional vs. non-functional;
static vs. initialization vs. dynamic; one-sided vs. two-sided.
The current version only includes the functional vs. non-functional
categorization. The other categories will be included in future
versions.
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4.1. Functional vs. non-functional
4.1.1. Functional features
What is delivered (delivery type):
o message-oriented delivery: SCTP UDP UDP-Lite DCCP
o byte-stream-oriented delivery: TCP
o object-oriented delivery of discrete data or file items: NORM
Reliability of delivery:
o non-reliable delivery: UDP UDP-Lite DCCP
o reliable delivery: TCP NORM
o reliable or partially reliable delivery: SCTP
o drop notification: DCCP
Direction of communication:
o unidirectional: UDP
o bidirectional: TCP
Ordered or unordered delivery:
o ordered delivery: DCCP
o ordered delivery for each byte stream: TCP
o ordered delivery for each byte or message stream: NORM
o ordered and unordered delivery within a stream (of messages): SCTP
o unordered delivery: UDP-Lite UDP
o unordered delivery of in-memory data or file bulk content objects:
NORM
Unicast, anycast, multicast or broadcast:
o unicast: TCP SCTP UDP UDP-Lite DCCP NORM
o IPv6 multicast and anycast: UDP
o IPv4 broadcast, multicast and anycast: UDP UDP-Lite
o multicast: NORM
4.1.2. Non-functional features
These are features that the application can optionally specify. If a
feature is not specified by the application it is undefined, i.e. the
TAPS system may choose an implementation of any of the features
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listed.
Congestion control:
o congestion control: TCP SCTP NORM
o no congestion control: UDP
Resilience:
o multihoming: SCTP
o no resilience: UDP UDP-lite TCP
Connection oriented (or not):
o connection oriented: TCP DCCP SCTP
o not connection oriented: UDP UDP-Lite
Message sizes and fragmentation:
o user message fragmentation and reassembly: SCTP
o IPv6 jumbograms: UDP
Setup negotiation:
o connection setup with feature negotiation and application-to-port
mapping: TCP SCTP DCCP
Flow control:
o flow control: TCP SCTP
o flow control (slow receiver function): DCCP
o flow control (timer-based and/or ack-based): NORM
o no flow control: UDP
Multiplexing:
o multistreaming: SCTP
o port multiplexing: TCP SCTP UDP UDP-Lite DCCP
o port multiplexing (UDP ports): NORM
o 2-tuple endpoints: UDP
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Transport layer mobility:
o transport layer mobility: SCTP
Error detection, protection, FEC and integrity (divided into more
groups?):
o partial integrity protection: UDP-Lite DCCP
o checksum optional: UDP
o error detection (checksum): TCP UDP
o error detection (UDP checksum): NORM
o strong error detection (CRC32C): SCTP
o packet erasure coding (both proactively and as part of ARQ): NORM
o content privacy to in-path devices: ? (intro of [TAPS1])
Streams:
o stream-oriented delivery in a single stream: TCP NORM
o support for multiple concurrent streams: SCTP
o support for stream scheduling prioritization: SCTP
Bundling:
o data bundling (Nagle's algorithm): TCP NORM
o user message bundling: SCTP
4.2. Components from draft-ietf-taps-transports-04 that are not
specified or seen by the applications
Segmentation:
o segmentation: TCP NORM
Timestamps:
o timestamps: DCCP
o Service Codes: DCCP
5. Acknowledgements
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).
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6. IANA Considerations
XX RFC ED - PLEASE REMOVE THIS SECTION XXX
This memo includes no request to IANA.
7. Security Considerations
Security will be considered in future versions of this document.
8. Normative References
[TAPS1] Fairhurst, G., Trammell, B., and M. Kuehlewind, "Services
provided by IETF transport protocols and congestion control
mechanisms", draft-ietf-taps-transports-04 (work in
progress), May 2015.
Authors' Addresses
Stein Gjessing
University of Oslo
PO Box 1080 Blindern
Oslo, N-0316
Norway
Phone: +47 22 85 24 44
Email: steing@ifi.uio.no
Michael Welzl
University of Oslo
PO Box 1080 Blindern
Oslo, N-0316
Norway
Phone: +47 22 85 24 20
Email: michawe@ifi.uio.no
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