ISO/IEC 14476-4:2010
(Main)Information technology — Enhanced communications transport protocol: Specification of QoS management for duplex multicast transport — Part 4:
Information technology — Enhanced communications transport protocol: Specification of QoS management for duplex multicast transport — Part 4:
ISO/IEC 14476-4:2010 provides a specification of QoS management for accomplishing desirable QoS for a duplex multicast transport connection. For this purpose, it describes the QoS management operations in duplex multicast transport connection such as QoS negotiation, QoS monitoring and QoS maintenance. ISO/IEC 14476-4:2010 is an integral part of ECTP-3 (ITU-T Rec. X.607 | ISO/IEC 14476-3). All of the protocol components, including packet formats and protocol procedures specified in ITU-T Rec. X.607 | ISO/IEC 14476-3 are also valid in ISO/IEC 14476-4:2010.
Technologies de l'information — Protocole de transport de communications amélioré: Spécification de la gestion de QoS pour le transport duplex en multidiffusion — Partie 4:
General Information
Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 14476-4
First edition
2010-05-01
Information technology — Enhanced
communications transport protocol:
Specification of QoS management for
duplex multicast transport
Technologies de l'information — Protocole de transport de
communications amélioré: Spécification de la gestion de QoS pour le
transport duplex en multidiffusion
Reference number
ISO/IEC 14476-4:2010(E)
©
ISO/IEC 2010
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ISO/IEC 14476-4:2010(E)
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ISO/IEC 14476-4:2010(E)
CONTENTS
Page
1 Scope. 1
2 Normative references . 1
3 Definitions . 1
3.1 Terms defined in Rec. ITU-T X.605 | ISO/IEC 13252 . 1
3.2 Terms defined in Rec. ITU-T X.606 | ISO/IEC 14476-1. 1
3.3 Terms defined in Rec. ITU-T X.606.1 | ISO/IEC 14476-2. 2
3.4 Terms defined in Rec. ITU-T X.607 | ISO/IEC 14476-3. 2
4 Abbreviations . 2
4.1 Packet types. 2
4.2 Miscellaneous . 3
5 Overview. 3
6 Components for QoS management. 5
6.1 Base header. 5
6.2 QoS parameters . 6
6.3 QoS extension element. 7
6.4 Acknowledgement element . 7
6.5 Packets used for QoS management . 8
7 QoS negotiation for duplex multicast connection . 8
7.1 Negotiation procedures. 9
7.2 QoS negotiation in the tree hierarchy . 10
7.3 Resource reservation. 10
8 QoS monitoring and maintenance for the forward channel . 10
8.1 QoS monitoring for the forward multicast channel. 11
8.2 QoS maintenance for the forward multicast channel. 13
9 QoS monitoring and maintenance for the backward channel. 15
9.1 QoS monitoring for the backward unicast channel . 15
9.2 QoS maintenance for the backward unicast channel . 16
Annex A – Implementation considerations. 18
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ISO/IEC 14476-4:2010(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 14476-4 was prepared by ITU-T (as ITU-T Rec. X.607.1) and was adopted, under a special
“fast-track procedure”, by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel with
its approval by the national bodies of ISO and IEC. The identical text is published as ITU-T
Rec. X.607.1 (11/2008).
ISO/IEC 14476 consists of the following parts, under the general title Information technology — Enhanced
communications transport protocol:
⎯ Part 1: Specification of simplex multicast transport
⎯ Part 2: Specification of QoS management for simplex multicast transport
⎯ Part 3: Specification of duplex multicast transport
⎯ Part 4: Specification of QoS management for duplex multicast transport
⎯ Part 5: Specification of N-plex multicast transport
⎯ Part 6: Specification of QoS management for N-plex multicast transport
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ISO/IEC 14476-4:2010(E)
Introduction
This Recommendation | International Standard specifies the Enhanced Communications Transport Protocol (ECTP),
which is a transport protocol designed to support Internet multicast applications running over multicast-capable
networks. ECTP operates over IPv4/IPv6 networks that have the IP multicast forwarding capability with the help of
IGMP and IP multicast routing protocols, as shown in Figure 1. ECTP could possibly be provisioned over UDP.
Figure 1 – ECTP Model
ECTP is designed to support tightly controlled multicast connections in simplex, duplex and N-plex applications.
ECTP part 4 QoS management (this Recommendation | International Standard) specifies the quality of service (QoS)
management functionality for stable management in the duplex multicast connection. The QoS management
functionality consists of QoS negotiation, QoS monitoring and QoS maintenance operations. The procedures of
reliability control in duplex connection have been defined in ECTP part 3 (Recommendation ITU-T X.607 |
ISO/IEC 14476-3).
In ECTP-3 duplex multicast connection, the participants are classified into one Transport Connection Owner
(TC-Owner) and many Transport Services users (TS-users). TC-Owner will be designated among the TS-users before
the connection begins. In the duplex multicast connection, the two types of data transports are supported: multicast data
transport from TC-Owner to all the other TS-users and unicast data transport from TS-users to TC-Owner. After the
connection is created, TC-Owner can transmit multicast data to the group, whereas each TS-user is allowed to send
unicast data to TC-Owner just after it gets a token from the TC-Owner.
For QoS management in the duplex multicast connection, the TC-Owner triggers the connection creation process. Some
or all of the enrolled TS-users will participate in the connection and become the designated "active TS-users". The
TS-users who are active at this stage are able to participate in negotiating the desired QoS level for the session. In the
duplex multicast connection, TS-users can send the data to TC-Owner, which each TS-user negotiates with TC-Owner
for a QoS parameter for backward unicast data channel. TC-Owner proposes the target value of QoS parameter for
forward multicast data channel and backward unicast data channel. If QoS negotiation is enabled, each TS-user can
propose modified values of QoS parameters for forward multicast data channel and backward unicast data channel.
TC-Owner arbitrates these modified values of QoS parameters for two types of data transport. These arbitrated values
are delivered to TS-users via subsequent Heartbeat (HB) or Join Confirm (JC) packets, and will be used for QoS
monitoring and maintenance. Any enrolled TS-user that is not active at this stage may participate in the connection as a
late-joiner, but will have to accept the established QoS level.
After the connection is created, TC-Owner begins to transmit multicast data and some of TS-users who get a token from
TC-Owner can send unicast data to TC-Owner. While the connection is active, TC-Owner monitors the status of the
session via feedback control packets from the active TS-users.
TC-Owner may take a range of actions if network problems (such as severe congestion) are indicated by the feedback
received from active TS-users. These actions include adjusting the data transmission rate, suspending multicast data
transmission temporarily, or in the last resort, terminating the connection.
ECTP part 4 QoS management Specification can be used by the multicast applications that require supporting various
QoS requirements and the corresponding billing/charging models.
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ISO/IEC 14476-4:2010 (E)
INTERNATIONAL STANDARD
RECOMMENDATION ITU-T
Information technology – Enhanced communications transport
protocol: Specification of QoS management
for duplex multicast transport
1 Scope
This Recommendation | International Standard provides a specification of QoS management for accomplishing
desirable QoS for a duplex multicast transport connection. For this purpose, this Specification describes the QoS
management operations in duplex multicast transport connection such as QoS negotiation, QoS monitoring and QoS
maintenance. This Recommendation | International Standard is an integral part of ECTP-3 (Rec. ITU-T X.607 |
ISO/IEC 14476-3). All of the protocol components, including packet formats and protocol procedures specified in
Rec. ITU-T X.607 | ISO/IEC 14476-3, are also valid in this Recommendation | International Standard.
2 Normative references
The following Recommendations and International Standards contain provisions which, through reference in this text,
constitute provisions of this Recommendation | International Standard. At the time of publication, the editions indicated
were valid. All Recommendations and Standards are subject to revision, and parties to agreements based on this
Recommendation | International Standard are encouraged to investigate the possibility of applying the most recent
edition of the Recommendations and Standards listed below. Members of IEC and ISO maintain registers of currently
valid International Standards. The Telecommunication Standardization Bureau of the ITU maintains a list of currently
valid ITU-T Recommendations.
– Recommendation ITU-T X.601 (2000), Multi-peer communications framework.
– Recommendation ITU-T X.602 (2004) | ISO/IEC 16513:2005, Information technology – Group
management protocol.
– Recommendation ITU-T X.605 (1998) | ISO/IEC 13252:1999, Information technology – Enhanced
Communications Transport Service Definition.
– Recommendation ITU-T X.606 (2001) | ISO/IEC 14476-1:2002, Information technology – Enhanced
Communications Transport Protocol: Specification of simplex multicast transport.
– Recommendation ITU-T X.606.1 (2003) | ISO/IEC 14476-2:2003, Information technology – Enhanced
Communications Transport Protocol: Specification of QoS management for simplex multicast transport.
– Recommendation ITU-T X.607 (2007) | ISO/IEC 14476-3:2008, Information technology – Enhanced
communications transport protocol: Specification of duplex multicast transport.
– Recommendation ITU-T X.608 (2007) | ISO/IEC 14476-5:2008, Information technology – Enhanced
communications transport protocol: Specification of N-plex multicast transport.
3 Definitions
3.1 Terms defined in Rec. ITU-T X.605 | ISO/IEC 13252
This Recommendation | International Standard is based on the concepts developed in Enhanced Communications
Transport Service (Rec. ITU-T X.605 | ISO/IEC 13252):
a) QoS parameters;
b) QoS negotiation;
c) QoS arbitration.
3.2 Terms defined in Rec. ITU-T X.606 | ISO/IEC 14476-1
This Recommendation | International Standard is described based on the concepts and terms developed in the
specification of simplex multicast transport on ECTP-1:
a) application;
b) packet;
Rec. ITU-T X.607.1 (11/2008) 1
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ISO/IEC 14476-4:2010 (E)
c) sender;
d) receiver;
e) tree;
f) parent;
g) child.
3.3 Terms defined in Rec. ITU-T X.606.1 | ISO/IEC 14476-2
This Recommendation | International Standard is described based on the concepts and terms developed in the
specification of simplex multicast transport on ECTP-2:
a) QoS monitoring;
b) QoS maintenance.
3.4 Terms defined in Rec. ITU-T X.607 | ISO/IEC 14476-3
This Recommendation | International Standard is described based on the concepts and terms developed in the
specification of duplex multicast transport on ECTP-3:
a) SU (Sending TS-User)
Some of the ECTP-3 TS-users can send unicast data to the TC-Owner. A sending TS-user (SU) is a
TS-user who gets a token from TC-Owner. Only the SU is allowed to send unicast data to TC-Owner. In
other words, before sending unicast data, each user must request a token to TC-Owner.
b) Token
It represents the rights for a TS-user to transmit data. The TS-user who has a token is called a Sending
TS-User (SU). The tokens are managed by TC-Owner.
c) Forward data channel
It represents the multicast data channel from TC-Owner to the group members. TC-Owner sends
multicast data to all the other group members over IP multicast address.
d) Backward data channel
It represents the unicast data channel, in which the data packet flows from an SU to TC-Owner. An SU
can send unicast data to TC-Owner over IP unicast address.
4 Abbreviations
For the purposes of this Recommendation | International Standard, the following abbreviations apply:
4.1 Packet types
ACK Acknowledgment
CC Connection Creation Confirm
CR Connection Creation Request
CT Connection Termination Request
DT Data
HB Heartbeat
HBACK Heartbeat Acknowledgment
JC Late Join Confirm
ND Null Data
TC Tree Join Confirm
TGC Token Get Confirm
TGR Token Get Request
TRC Token Return Confirm
TRR Token Return Request
2 Rec. ITU-T X.607.1 (11/2008)
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ISO/IEC 14476-4:2010 (E)
4.2 Miscellaneous
ADN Active Descendant Number
API Application Programming Interface
CHQ Controlled Highest Quality
Diffserv Differentiated Services
ECTP Enhanced Communications Transport Protocol
ECTP-5 Enhanced Communications Transport Protocol, part 5
ECTS Enhanced Communications Transport Services
IP Internet Protocol
LO Local Owner
LQA Lowest Quality Allowed
MSS Maximum Segment Size
OT Operating Target
QoS Quality of Service
RSVP Resource Reservation Protocol
5 Overview
This Recommendation | International Standard provides a specification of QoS management for duplex multicast
transport connections. This Specification describes the following QoS management operations:
a) QoS negotiation, including reservation of network resources;
b) QoS monitoring;
c) QoS maintenance.
In the connection creation phase, TC-Owner informs TS-users whether QoS management is enabled. If QoS
management is enabled, TC-Owner must also specify whether or not QoS negotiation will be performed in the
connection. QoS monitoring and maintenance operations are performed only if QoS management is enabled.
Figure 2 illustrates these QoS management operations for the duplex multicast connection. In the figure, the protocol
operations marked as dotted lines are specified in Rec. ITU-T X.607 | ISO/IEC 14476-3 (ECTP-3).
Rec. ITU-T X.607.1 (11/2008) 3
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ISO/IEC 14476-4:2010 (E)
Figure 2 – QoS management in the duplex connection
In this figure, it is noted that the basic control operations of the duplex multicast connection are described in ECTP-3,
such as the control tree creation, tree-based reliability control, control tree maintenance for forward multicast channel,
and the token control for backward channels in the duplex multicast connection. The QoS monitoring and maintenance
operations for forward multicast channel are specified in ECTP-2. In this Specification, the QoS negotiation for the
duplex multicast connection and the QoS monitoring and maintenance operations for 'backward unicast channel' will be
introduced.
From the requirements of the applications, TC-Owner will determine the target values for each QoS parameter. The
procedures of mapping the application's requirements to those target parameter values are outside the scope of this
Specification. Application programs could be used to carry out such mappings.
QoS negotiation is performed in the connection creation phase. TC-Owner proposes the desired target values for each
QoS parameter for forward multicast data channel and backward unicast data channel to all TS-users by multicast via
the CR message. For the throughput parameter, three target values are specified: controlled highest quality (CHQ),
operating target (OT) and lowest quality allowed (LQA). For the other parameters, such as transit delay, transit delay
jitter, and data loss rate, only two target values are specified: OT and LQA.
If QoS negotiation is enabled, each TS-user can propose modifications to the TC-Owner's proposed parameter values.
These modified values will be determined by considering the system capacity at TS-user side and network
environments. The following restrictions are imposed for modification of parameter's values by TS-users:
1) OT values must not be modified by TS-users;
2) the values modified by TS-users must be within LQA and CHQ values proposed by TC-Owner.
The parameter values modified by TS-users are delivered to TC-Owner via CC messages. TC-Owner arbitrates different
parameter values for various TS-users by taking a default range of values.
Figure 3 shows an abstract sketch of QoS negotiation that can occur in ECTP-4. From the application's requirements, a
set of target QoS parameter values for forward multicast data channel and backward unicast data channel will be
configured at TC-Owner. TC-Owner informs TS-users about the target values for forward multicast data channel and
backward unicast data channel (step 1). Based on those target values, each TS-user begins to make resource reservations
with the help of RSVP or Diffserv (step 2). If QoS negotiation is enabled in the connection, each TS-user may propose
modified values for QoS parameters for forward multicast data channel and backward unicast data channel (step 3).
From these modified parameter values, TC-Owner determines the arbitrated values (step 4). These arbitrated values are
delivered to TS-users via subsequent HB or JC packets, and will be used for QoS monitoring and maintenance.
4 Rec. ITU-T X.607.1 (11/2008)
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ISO/IEC 14476-4:2010 (E)
Figure 3 – QoS negotiation in the ECTP duplex connection
After an ECTP connection is created, and consequently if QoS management is enabled, the QoS monitoring and
maintenance operations are performed for forward multicast data channel and backward unicast data channel. For QoS
monitoring, each TS-user is required to measure the parameter values experienced for forward multicast data channel
and TC-Owner is required to measure the parameter values experienced for backward unicast data channel. Based on
the measured values and the negotiated values, a TS-user determines a parameter status value for each parameter as an
integer: normal (0), reasonable (1), possibly abnormal (2) or abnormal (3). These status values will be delivered to
TC-Owner via ACK packets. TC-Owner aggregates the parameter status values reported from TS-users. If a control tree
is employed, each parent Local Owner (LO) node aggregates the measured values reported from its children, and
forwards the aggregated value(s) to its own parent using ACK packets. In backward unicast data channel, these status
values will be delivered to sending TS-user from TC-Owner via HBACK used for retransmission request.
TC-Owner takes QoS maintenance actions necessary to maintain the connection status at a desired QoS level, based on
the monitored status values. Specific rules are pre-configured to trigger QoS maintenance actions such as data
transmission rate adjustment, connection pause, and resume, troublemaker ejection and connection termination. Those
actions will be taken by observing how many TS-users are in the abnormal or possibly abnormal state. In backward
unicast data channel, each sending TS-user will take the associated QoS maintenance actions based on the status values
contained in the HBACK packets delivered to the sending TS-user from TC-Owner.
6 Components for QoS management
This clause describes the ECTP-3 protocol components required for QoS management operations. All of the
components are extended from those already defined in Rec. ITU-T X.607 | ISO/IEC 14476-3.
6.1 Base header
Figure 4 shows the base header specified in Rec. ITU-T X.607 | ISO/IEC 14476-3 (in case of ECTP-3 over IP).
0 1 2
3
01 23 45 6 7 0 1 2 3 456 70 123 4 5 6 70 12 34 5 6 7
CT Packet type
Next element Version Checksum
Source port Destination port
Packet sequence number (PSN)
Payload length QN
F Reserved Token ID
X.607.1(08)_F04
Figure 4 – Base Header in ECTP-3
Rec. ITU-T X.607.1 (11/2008) 5
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ISO/IEC 14476-4:2010 (E)
For QoS management, TC-Owner additionally specifies the following two fields in the 'QoS' and 'N' bits:
0 1 2 3 4 5 6 7
F Reserved N Qos
a) QoS is a flag bit to indicate whether QoS management is enabled (1) or not (0) in the connection. If this
bit is set to '1', all the procedures for QoS management are invoked. The default value is '0';
b) N (Negotiation) is a flag bit to indicate whether QoS negotiation is enabled (1) or not (0) in the
connection. If this bit is set to '1', each TS-user is allowed to propose its own parameter values for
forward multicast data channel and backward unicast data channel. The default value is '0'.
The QoS bit must be set to "1" (QoS enabled) before the N bit is valid. There are three possible cases.
a) QoS bit set to "1" and N bit set to "0" indicates that QoS is to be used in the connection, and QoS values
will be imposed by TC-Owner. TS-users cannot negotiate it.
b) Both bits set to "1" indicates that QoS is to be used in the connection, and QoS parameter values may be
negotiated between TS-users and TC-Owner.
c) QoS bit set to "0" indicates that QoS is not to be used in the connection. The N bit is not used in this
case.
6.2 QoS parameters
As specified in ECTP-2, the following four QoS parameters are defined for duplex connection:
1) throughput (bytes per second);
2) transit delay (milliseconds);
3) transit delay jitter (milliseconds);
4) data loss rate (percent).
The throughput parameter represents an amount of application data output over a specific time period. Target
throughput means a throughput value required for desirable display of application data. In forward multicast data
transport, applications generate multicast data and TC-Owner will transmit them, based on the target throughput
value(s). If TS-user gets a token from TC-Owner to send unicast data, the applications at a sending TS-user side
generate unicast data for backward unicast data transport and the sending TS-user will transmit them to TC-Owner,
based on the target throughput value(s) from TC-Owner. Actual data reception rate at TS-user's side will depend on data
transmission rate, network conditions and end system capacity, etc.
For throughput, TC-Owner shall configure the following target values:
1) CHQ throughput;
2) OT throughput;
3) LQA throughput.
Among them, the following inequalities must be enforced: LQA throughput ≤ OT throughput ≤ CHQ throughput.
Transit delay represents end-to-end transmission time from a sender to a receiver. For desirable display of forward
multicast data and backward unicast data, TC-Owner may configure the following target values:
1) OT transit delay;
2) LQA transit delay.
Between them, the following inequalities must be enforced: OT transit delay ≤ LQA transit delay.
Transit delay jitter represents variations of transit delay values. For desirable display of forward multicast data and
backward unicast data, TC-Owner may configure the following target values:
1) OT transit delay jitter;
2) LQA transit delay jitter.
Between them, the following inequalities must be enforced: OT transit delay jitter ≤ LQA transit delay jitter.
6 Rec. ITU-T X.607.1 (11/2008)
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ISO/IEC 14476-4:2010 (E)
Data loss rate is defined as a ratio of the amount of lost data over the amount of totally transmitted data. For a desirable
display of forward multicast data and backward unicast data, TC-Owner may configure the following target values:
1) OT loss rate;
2) LQA loss rate.
Between them, the following inequalities must be enforced: OT loss rate ≤ LQA loss rate.
6.3 QoS extension element
QoS extension is a newly defined element for QoS management in this Specification. All the extension elements used in
ECTP-4 are listed below.
Table 1 – Extension elements of ECTP-4
Encoding value in next Length of extension
Extension element
element (4 bits) element (bytes)
No element 0000 0
Connection 0001 4
Acknowledgment 0010 Varied
Membership 0011 4
Timestamp 0100 12
QoS 0101 28
Address 0110 8 or 20
The QoS extension element specifies the maximum segment size (MSS) and the target values for ECTP-2 QoS
parameters, which is described in ECTP-2. For a more detailed structure of the QoS extension element, refer
to ECTP-2.
The QoS element is used for the TC-Owner to inform the TS-users about the target values for QoS parameters for
forward multicast data transport and backward unicast data transport by sending a CR packet in the connection creation
phase. In QoS negotiation, the QoS element is also used when a TS-user proposes its own modified values to
TC-Owner. The negotiated QoS values will be announced to late-joiners via the JC packet and to existing TS-users via
HB packets.
These QoS values are also referred to by TS-users in the QoS monitoring and maintenance operations.
6.4 Acknowledgement element
For QoS monitoring, each TS-user is required to measure the parameter values that have been experienced. A measured
parameter value is mapped to a parameter status value. A status value is an integer such as 0, 1, 2 or 3. A larger status
value indicates a worse status for the connection.
For forward multicast data transport the status values are delivered to TC-Owner via ACK pac
...
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