Transcript 16Lanting

Multimedia Services using IP
over Bearer Networks:
Quality of Service Aspects
based on ACTS Guidelines SII G05 and SII G10
presented by
Cees J.M. Lanting
Datsa Belgium sprl, Belgium
ACTS projects EURORIM and PRIME
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Overview
• Assuming a 3 layer model
– applications and information services
– an overlay IP based application networks
– underlying telecom bearer network(s)
• Different origins IP and Telecom networks
• Expressing QoS requirements
• Meeting known QoS requirements in an IP based
overlay network
• Conclusions
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Different origins
• Telecom networks have been developed to support
and meet the requirements of sets of services:
– each service has precisely defined requirements for
the underlying services
• internet originates from the datacommunications and
dataprocessing environment:
– applications designed to work with what is available
– application requirements flexible and tolerant
– best effort therefore often acceptable
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Precise QoS requirements
• often assumed precise QoS requirements are
known, implicitly or explicitly
• however, QoS requirements may not actually be
known, or be known accurately
• useful to make a classification of application
services on the basis of their ability to accurately
express QoS requirements, either implicitly or
explicitly
• the ability to express QoS requirements is not the
same for different communication modes
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Expressing QoS requirements
• Type I
Connection-Less (CL) mode services,
characterised by undefined flow related QoS
requirements
• Type II
Connection (CO) mode services with
weakly defined flow related QoS requirements:
‘weak flow CO mode’
• Type III
Connection (CO) mode services with
well defined flow related QoS requirements:
‘strong flow CO mode’
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Expressing QoS requirements
• Type I
CL mode; for example,
– e-mail
– DNS
• Type II
weak flow CO mode; for example,
– file transfer
• Type III
strong flow CO mode; for example,
– videoconferencing
– speech
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Example: web access
The nature of web access incurs unknown QoS
requirements:
• low to medium requirements for navigation
• QoS requirements imposed on the fly by application
server - terminal, such as:
– medium to high bandwidth, non real-time (e.g. ftp)
– low to medium bandwidth real-time (voice, audio)
– high bandwidth real-time (video)
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Example (telecom): fixed-mobile
call
• Also in telecom QoS may not always be known
accurately
• for example, when a call is made originating from
a fixed network, with as destination, directly or
after deflection, a mobile network subscriber:
fixed network versus mobile network QoS
requirements
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Meeting known QoS requirements
in an IP based overlay network
• current generation IP suite differs significantly in its
nature from typical telecommunications protocols and
services; it does not provide for a defined flow
related QoS
• Extension protocols have been defined or proposed
to add support for different QoS classes, and different
QoS strategies have been proposed
• The next generation IP also provides mechanisms for
management and control of network resources
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Meeting QoS requirements in current
generation IP based overlay network
• basic IPv4 suite of protocols does not provide for the
– management and
– control of network resources
necessary to achieve a defined flow related QoS
• different QoS strategies have been proposed, for example
– controlled load,
– guaranteed service
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Meeting QoS requirements in next
generation IP based overlay
network
• Extension protocols have been defined or proposed
to add support for different QoS; mechanisms
proposed include resource reservation (RSVP)
• Next generation IP suite, IPv6, also provides
mechanisms for management and control of network
resources, through labelling and priority indication of
flows; these mechanisms can be used also in
combination with extension protocols
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
A comparison, from a network capabilities point of view
Aspect
orientation
control
at
network
level
congestion
control
typical telecom
network
basic IPv4 suite
extended IP suite
(RSVP, tag, IPv6)
CO
CL
CL, extended to CO/CL




 distributed
 loose
 distributed
 loose
 islands of strong cooperation
distributed, using
distributed, using
 TE congestion
measures
 TE congestion
measures
 QoS mechanisms
 “overrun”
co-ordinated
strong
imposed and enforced
transferable between
networks
co-ordinated, transferable
between networks, using
 policing & enforcement
 QoS mechanisms
 “overrun”
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
 “overrun”
A comparison, from a network capabilities point of view (cont.)
Aspect
typical telecom
network
QoS
management
co-ordinated, transferable
between networks, using
 network management
- errors
- statistics
 three party parameter
exchange
 priority indication
 policing, flow control
 preservation of
commitments and
obligations
QoS strategy
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
basic IPv4 suite
extended IP suite
(RSVP, tag, IPv6)
distributed, using
distributed, using
 network management
- errors
- statistics
 network management
- errors
- statistics
 three party parameter
exchange
 priority indication
 best effort
 controlled load
 guaranteed service
 best effort
 controlled load
 guaranteed service
Conclusions
• applications and multimedia services cover a wide
range of QoS requirements; they also differ in their
abilities to communicate their QoS requirements
• switched telecom networks are capable of providing
a guaranteed, or a near-guaranteed flow related QoS
• an IP application network overlaying telecom
networks used as bearer networks, the IP network
hides the underlying network(s) from the application;
bearer networks can only indirectly contribute to the
QoS provisioning in the IP application network
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Conclusions (cont.)
• In an IPv4 only based application network, the
QoS management will be limited, restricted to
strategies as best effort, controlled load and
guaranteed service
• In an extended or IPv6 based application network,
additional facilities are available to QoS
management; the application network may use
facilities in the bearer networks other than in an
averaged way
• difficult to provide in an open environment the
same levels of QoS possible in telecom networks
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
Relation with network
organisation
• Horizontal network organisation has an impact on
the possible co-ordination or ‘transferability’ of
control across network domains: for example,
‘priority’
• Also more generally, networks may have
limitations with respect to the horizontal
organisation: for example, lack of ‘visibility’
AIMS’99 Workshop
Heidelberg, 11-12 May 1999
High QoS versus other
approaches
As an alternative to providing a guaranteed high
level of QoS, other ways may be explored:
• provide users required QoS in relation with
charging; a possible mechanism would be based
on a link between the QoS and charging
AIMS’99 Workshop
Heidelberg, 11-12 May 1999