TITRE Adaptive Packet Video Streaming Over IP Networks - LaBRI

3.2.5 IP Signaling Protocols for Packet Video Applications
Signaling protocols over IP networks such as the Internet offer intelligent network services to
the applications in particular packet video applications. Two core signaling protocols are discussed
in these subsections. The first category is related to QoS signaling protocol such as RSVP,
RTP/RTCP, and COPS. The second category concerns session signaling protocol such as H.323,
SIP, and MPEG-4 DMIF.
3.2.5.1 QoS Control Signaling Protocols
QoS Control signaling protocols are defined in order to provide Quality of Service support
between network nodes and the applications. The signaling protocol defines a set of algorithms,
messages, and parameters used by the network to assure Quality of Service to user traffic. In
particular, QoS signaling helps to provide differentiated delivery services for individual flows or
aggregates, network provisioning, admission control, service guarantee, control load service, etc.
Dynamic QoS management could be provided using QoS signaling protocols.
We present in the following subsections two QoS signaling mechanisms which were developed
to implement Integrated Services Framework and Differentiated Services Framework. These
protocols are RSVP (Resource Reservation Protocol) and COPS (Common Open Policy Service).
3.2.5.1.1 RSVP
RSVP (Resource Reservation Protocol) [136] is a signaling protocol for resource reservation in
IP networks. Communally it is used for Intserv architecture (controlled load and guarantee service).
RSVP is an object-based message protocol which provides mechanisms to the application to
request a specific QoS from the network. RSVP carries the request through the network, visiting
each network element and attempts to make a resource reservation for the stream. To make a
resource reservation, the RSVP communicates with two local decision modules, admission control and
policy control. Admission control determines whether the network element has sufficient available
resources to supply the requested QoS. Policy control determines whether the user has
administrative permission to make the reservation. RSVP supports both multicast and unicast
traffic, for IPV4 and IPV6 clients.
3.2.5.1.2 COPS Protocol
The COPS (Common Open Policy Service) [137] Protocol is a QoS signaling protocols
supporting policy control over a simple client/server model. The protocol describes a simple query
and response protocol that can be used to exchange policy information between a policy server
(Policy Decision Point or PDP) and its clients (Policy Enforcement Points or PEPs). One
example of a policy client is an RSVP router that must exercise policy-based admission control over
RSVP usage (COPS-RSVP) [138] or a Diffserv client that receives configuration information about
Diffserv elements like meter, classifier, scheduler, shaper, etc. (COPS-PR) [139].
3.2.5.2 Session Control Signaling Protocol
Packet video application has grown rapidly in the last few years. This rapid expansion and
potential is essentially due to standardization bodies that enable protocols and services. Actually, it
appears likely that both IETF SIP (Session Initiation Protocol) [140] with SDP (Session
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