IP NETWORK SERVICE QUALITY MANAGEMENT BY DISTRIBUTED
ADMISSION CONTROL BASED ON A SIGNALING PROTOCOL
The invention relates to a procedure and a device making it
possible to manage service quality hop-by-hop within a communications
network comprising several arteries linked together by a routing device for
example.
The invention applies in respect of multimedia stream transport on
a meshed network based on the IP protocol (Internet Protocol).
In certain telecommunication networks, the management of
service quality at a global level, differentiated or Diffserv services, is not
sufficient. It turns out also to be necessary to dynamically manage
connection-oriented streams each having specific quality of service (QoS)
parameters such as precedence, latency time, jitter, loss sensitivity,
bandwidth.
For each of these streams, it is necessary to manage:
o The admission control for connections with a signaling protocol,
o The routing of the streams in a meshed network according to the
availability of the resources in the network,
o The control of the sending of the user data in accordance with the
reservations previously performed.
Stream-based management of quality of service is based mainly
on the mechanisms for reserving resources which take account of the quality
of service or QoS parameters. The reservation of the resources is based on
signaling protocols (H.323 or SIP).
DiffServ offers three classes of service:
o The service class corresponding to the maximum priority which makes
it possible to minimize the delay and its variation for real-time traffic or
Expedited Forwarding (EF) is assumed to be used for multimedia and
video services requiring real-time capabilities (latency time, jitter).
o The service class which allows the transmission of the data without
taking account of the latencies or of the variations in delay or Assured
Forwarding (AF) is assumed to be used for the data services which
demand bandwidth guarantees (bandwidth, low losses).
o The low priority or Best Effort (BE) service class which is used for the
services not having any bandwidth, latency time or jitter constraint.
The DiffServ model has not standardized any signaling protocol, to
avoid the storage of contexts in the routers. This model has been developed
by the IETF to solve the switchover to Internet scale. The DiffServ model has
been specified for telecommunications network operators. This model
requires a scheduling of the network corresponding to the level of service
required by the users connected to the network. This model operates
correctly if the core of the network has sufficient resources and if these
resources are correctly scheduled. Generally, the network resources are
explicitly reserved by the operator for the network established for its client. In
the case of applications having global mobility constraints and/or constraints
of resources present in the core of the network that are below the global
requirements, the scheduling of resources is no longer possible.
For these cases, it turns out useful:
o to reserve resources forming part of a Service class for the time of a
communication. This reservation is performed with a signaling
protocol.
o to supply these resources to the system when the communication is
terminated, typical case is speech communication.
The procedure according to the invention relies notably on the
following principles:
o the reservation of resources is managed by a connections admission
control mechanism, which controls the establishment of the streams
according to: the type of communication, the resources available and
also the precedence of the communication.
o because of the frequent changes of topology of the network, the
connections admission control (CAC) is present in each node of the
network and therefore is distributed over the network. The CAC
function, as in a connection-oriented network, reserves the resources
gradually during the establishment of the connection. These resources
are reserved on the communication support arteries.
o a specific routing protocol can be developed to take account of the
evolution of the reservation of resources on the arteries of the network
core (QoS routing, flooding route search, etc.).
o once the communication has been established the procedure ensures
that all the packets of one and the same connection follow the route
on which the resources have been reserved for this communication.
The invention relates to a procedure for managing the quality of
service hop-by-hop in a packet-based communications network comprising
several arteries linked together by a router, the network supporting a
signaling protocol, characterized in that it comprises at least at each router a
step of reserving the resources on the arteries hop-by-hop and a step
ensuring once the communication has been established that the packets of
one and the same connection follow the path between the sending source
and the destination on which the resources have been reserved.
The resource reservations are for example performed during the
propagation of the network core signaling.
The procedure can comprise the following steps:
• Establish and release, dynamically, circuits required either by the
application package level; or by a user,
• Reserve the resources on the arteries for each established circuit; with
each reservation is associated the bandwidth, the precedence of the
reservation, and the service class which encompasses this resource,
• Ensure the preemption of a communication, if there are not sufficient
resources available for a new communication having a higher priority
level.
The routing is for example based:
o either on the trunking table present in the routers
o or on an application package level routing protocol.
The procedure for example uses an IP network.
The invention also relates to a device for managing the quality of
service hop-by-hop in a communications network comprising several arteries
linked together by means of a router, and a signaling protocol, characterized
in that each router or node of the network comprises a means suitable for
reserving the resources gradually and a means suitable for guaranteeing that
4
Preliminary Amendment
the packets of one and the same communication follow the same route on
which the signaling protocol has previously reserved the resources for the
communication.
The device for example comprises means suitable for:
• establishing and releasing in a dynamic manner the circuits required
either by the application package level, or by a user,
• routing the communications according to trunking tables (present in
the router or formulated by a routing protocol taking account of the
reservations performed),
• reserving the resources on the arteries for each established circuit;
and associating with each reservation the bandwidth, the precedence
of the reservation, and the service class which encompasses this
resource,
• managing the preemption of a communication if there are not sufficient
resources available for a new communication having a higher priority
level.
The network is for example a meshed network based on the IP
protocol.
The invention also relates to a component for managing the quality
of service within a communications network comprising several arteries,
comprising at least the following elements:
• an interface for configuring the system,
• an interface for managing the arteries,
• a resources manager,
• a stack of signaling protocols,
• an interface with the user signaling,
• an interface with the network signaling,
• an integrated routing protocol,
• a module for controlling the resources manager.
The invention has in particular the following advantages:
It makes it possible in particular to control the state of the resource
reservations of an artery on a telecommunications network before
propagating the call which is the subject of a multimedia communication, for
example. The control being carried out at each hop at the level of each artery
of a meshed network, the quality of service of the multimedia communication
can, in this way, be guaranteed end-to-end.
The type of organization according to the invention offers the
advantage of operating when the bandwidth available on the arteries of the
network is low, since it allows the implementation of connections admission
control mechanisms on the arteries of the communications network.
The organization also makes it possible to ensure that the packets
of one and the same communication all follow the same route on which the
signaling protocol has previously reserved the resources for the
communication, while the IP routing can designate other optimal routes.
The system which is the subject of the present invention also
allows the reservation of network resources for the OODA (or Observe Orient
Decide and Act) loops of NCW (Network Centric Warfare) applications.
Other characteristics and advantages of the invention will be more
clearly apparent on reading the description which follows of an example
given by way of wholly non limiting illustration accompanied by the figures
which represent:
o Figure 1 a functional chart of the procedure according to the invention,
o Figure 2 a general chart presenting the various issues dealt with by
the procedure according to the invention,
o Figure 3 an exemplary architecture of a communications network
using the procedure.
In order to better elucidate'the invention, the description which
follows given by way of wholly nonlimiting illustration relates to a
telecommunications network using the Diffserv model combined with a
signaling protocol making it possible to control the network resources.
Hop-by-hop routing can be likened to the creation of a circuit network in
parallel or overlay on a datagram network core. The overlay circuit operates
on a set of private links installed in a shared operator infrastructure, for
example.
The circuits are established dynamically with a signaling protocol,
such as H.323 or SIP developed by international bodies. The circuit
establishment request is made by the user who requires an application
package circuit for a given stream (example: speech stream,
videoconferencing, etc.). The establishment of the circuit is managed by a
local server LCC (Local Call Control, H.323 Gatekeeper, SIP server).
The network core signaling is also based on the ITU or IETF standards
(H.323, SIP). This signaling propagates in the network core the requirement
of the user or of the application. The resource reservations are performed
gradually during this propagation.
Figure 1 shows diagrammatically a functional chart of a
component for managing the quality of service according to the invention.
It comprises for example:
o An interface for configuring the system or ACS 1;
o An interface for managing the arteries 2;
o An interface for controlling the router 3;
o A resources manager or CAC having in particular as functions: the
connection, the admission, the allocation of the resources with the
passage of time, and the management of the preemptions of the
communications 4;
o A stack of signaling protocols 5;
o An interface with the user signaling (LCC) 6;
o An interface with the network signaling (QSM) 7;
o An integrated routing protocol 8;
o A general control module for the QSM resources manager 9.
The general control module 9 is in particular charged with the
distribution of the artery level information (state, topology, bandwidth, etc.) to
the internal QSM modules (routing, CAC management). This module is also
charged with the reconfiguration of the queues of the router, if the bandwidth
available on the link changes.
The CAC module 4 stores the resources reservation performed
during the establishment of the circuits. For each reservation, this module
stores the bandwidth reservation, the precedence and also the service class
(EF, AF1, AF2). These parameters are used to perform the admission control
for the new connections.
The CAC module formulates a calculation of average latency for
the communication. If this latency exceeds an admissible maximum for the
communication, the admission control rejects the communication (for
example, in the case where there are more than 2 satellite hops for a
telephone call). The latency of the communication is the sum of all the
latencies of the communication (compression, latencies of the arteries,
buffering).
The routing and discovery module 8 might not be present
according to the protocols used. In this case, the QSM module reads the
routing table to obtain the route or routes to the destination server (LCC) and
propagates the connection request on this route.
The signaling stack 5 takes into account the access protocol
managed by the LCC and manages the signaling protocols propagated on
the network. These protocols comply with the standards established by the
ITU and the IETF. Complementary information, necessary for the
establishment of the communication, is transported in a user to user
information element (UUIE), for example, the destination server address, the
precedence of the communication, the average latency on the route, etc.
Functionally, the procedure according to the invention operates in
the following manner. The procedure ensures:
• Dynamically the establishment and the releasing of the circuits
required either by the application package level, or by a user
(telephony, for example);
• The reservation of resources on the arteries for each established
circuit; with each reservation is associated the bandwidth, the
precedence of the reservation, and the service class which
encompasses this resource,
• The preemption of a communication, if there are not sufficient
resources available for a new communication having a higher priority
level,
• The routes making it possible to reach the destination LCC server in
charge of the communication; the routing can be based:
o Either on the trunking table present in the routers, in this case,
the establishment is dispatched to the destination server (LCC)
according to the optimal route formulated by the router's routing
protocol, in the event of equivalent routes, it is possible to
explore alternative routes,
o Or on an application package level routing protocol (QoS
routing, flooding route search, etc.)
• The successive packets of one and the same stream are trunked on
the same arteries, even when the topology of the network changes.
Figure 2 shows diagrammatically a chart comprising in its upper
part, the actions managed conventionally by a router according to the prior
art and in its lower part the various issues dealt with by the procedure
according to the invention designated QSM.
Figure 3 represents an exemplary implementation of the procedure
within a network comprising several QSM routers according to the invention.
The routers are linked by arteries. A router is connected to an LCC
destination server.

CLAIMS
1 - A method for managing the quality of service hop-by-hop in a packetbased
communications network comprising several arteries linked together
by a router, the network supporting a signaling protocol, characterized in that
it comprises at least at each router the following steps:
• Dynamically the establishment and the releasing of the circuits
required either by the application package level, or by a user,
• The reservation of resources on the arteries for each established
circuit; with each reservation is associated the bandwidth, the
precedence of the reservation, and the service class which
encompasses this resource,
• The preemption of a communication, if there are not sufficient
resources available for a new communication having a higher priority
level.
2 - The method as claimed in claim 1, characterized in that the resource
reservations are performed during the propagation of the network core
signaling.
3 - The method as claimed in claim 2, characterized in that the routing is
based:
o either on the trunking table present in the routers
o or on an application package level routing protocol.
4 - The method as claimed in one of claims 1 to 3, characterized in that it
uses an IP network.
5 - A device for managing the quality of service hop-by-hop in a
communications network comprising several arteries linked together by
means of a router, and a signaling protocol, characterized in that each router
or node of the network comprises a means suitable for:
• establishing and releasing in a dynamic manner the circuits required
either by the application package level, or by a user;
• routing the communications according to trunking tables,
• reserving the resources on the arteries for each established circuit;
and associating with each reservation the bandwidth, the precedence
of the reservation, and the service class which encompasses this
resource,
• managing the preemption of a communication if there are not sufficient
resources available for a new communication having a higher priority
level.
6 - The device as claimed in claim 5, characterized in that the network is a
meshed network based on the IP protocol.
7 - A component for managing the quality of service within a communications
network comprising several arteries according to a method of one of claims 1
to 4, comprising at least the following elements:
• an interface for configuring the system,
• an interface for managing the arteries,
• a resources manager,
• a stack of signaling protocols, :
• an interface with the user signaling,
• an interface with the network signaling,
• an integrated routing protocol,
• a module for controlling the resources manager.