Electrical computers and digital processing systems: multicomput – Computer-to-computer session/connection establishing – Network resources access controlling
Reexamination Certificate
1999-06-07
2003-07-08
Vu, Viet D. (Department: 2154)
Electrical computers and digital processing systems: multicomput
Computer-to-computer session/connection establishing
Network resources access controlling
C709S249000, C709S241000, C370S401000
Reexamination Certificate
active
06591301
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to methods and systems for controlling a network gatekeeper. More particularly, the present invention relates to methods and systems for controlling message processing by an H.323 gatekeeper.
RELATED ART
H.323 is a set of recommendations from the International Telecommunications Union (ITU) for multi-media communications over local area networks (LANs) that do not provide guaranteed quality of service (QoS). These networks are commonly used in corporate and educational institutions. Exemplary packet-switched networks that do not guarantee quality of service include TCP/IP, UDP/IP, and IPX over Ethernet, Fast Ethernet and Token Ring. H.323 provides recommendations for communication between voice-only handsets, video conferencing stations, and other devices capable of transmitting voice, video, and data packets over such networks.
H.323 defines four major components for a network-based communication system: terminals, gateways, gatekeepers, and multi-point control units. Terminals are client endpoints connected to a LAN that provide real-time, two-way communications. A terminal may include a telephone capable of transmitting voice packets over a network, a video conferencing station capable of transmitting voice and video over a network, or a computer capable of transmitting voice, video, and data over a network. A gateway is an optional element of an H.323 network that provides translation between transmission formats and between communications procedures. For example, a gateway may establish links between H.323 terminals and analog public switched telephone network (PSTN) terminals. Thus, gateways function as translators between H.323 compliant devices and non-H.323 compliant devices.
A gatekeeper is the most important part of an H.323 enabled network. An H.323 gatekeeper functions as the central point for all calls within its zone and provides call control services to the registered endpoints.
FIG. 1
illustrates a conventional H.323 gatekeeper and an H.323 zone. In
FIG. 1
, an H.323 gatekeeper
100
manages message traffic in an H.323 zone
101
. An H.323 zone is defined by the collection of terminals, gateways, and multi-point control units managed by a single gatekeeper.
In the illustrated example, the H.323 zone
101
spans multiple networks
102
and
103
connected by routers
104
and
105
. The H.323 zone
101
includes terminals
106
-
110
that transmit packets containing multi-media data to each other in accordance with H.323 recommendations. A gateway
111
translates between transmission formats and communications procedures. A multi-point control unit (MCU)
112
supports conferences between three or more endpoints.
Gatekeepers perform two important call control functions. The first function is address translation from LAN aliases for terminals and gateways to IP or IPX addresses, as defined in the Registration, Admission, Status (RAS) specifications included in ITU Recommendation H.225. The second function is bandwidth management, which is also described in ITU Recommendation H.225. For example, a network manager may have a specific threshold for the number of simultaneous conferences on a local area network (LAN). The gatekeeper can refuse to make connections once the threshold is reached. The effect of refusing to make connections is to limit the total conferencing bandwidth to some fraction of the total available network bandwidth. The remaining bandwidth may be used for e-mail, file transfers, and other LAN protocols.
An optional, but valuable, feature of a gatekeeper is the ability to route H.323 calls. By routing a call through a gatekeeper, the call can be controlled more effectively. Service providers need this ability in order to bill for calls placed through their networks. This service can also be used to re-route a call to another endpoint if a called endpoint is unavailable. In addition, a gatekeeper capable of routing H.323 calls can assist in making decisions involving balancing among multiple gateways. For instance, if a call is re-routed through a gatekeeper, that gatekeeper can then re-route the call to one of the many gateways based on a balancing algorithm. While a gatekeeper is logically separate from H.323 endpoints, vendors may incorporate gatekeeper functionality into physical implementation of gateways and MCUs.
A gatekeeper is not required in an H.323 system. However, if a gatekeeper is present, terminals must make use of the services offered by the gatekeepers. RAS, as described in ITU Recommendation H.225, defines these services as address translation, admissions control, bandwidth control, and zone management.
Gatekeepers can also play a role in multi-point communications. To support multi-point conferences, users may employ a gatekeeper to receive control channels from two terminals in a point-to-point conference, as described in ITU Recommendation H.245. When the conference switches to multi-point, the gatekeeper can direct the H.245 control channel to a multi-point controller, or MC. The gatekeeper need not process the H.245 signaling; it only needs to pass the H.245 signals between the terminals or between the terminals and the MC.
LANs containing gateways can also contain a gatekeeper to translate incoming E.164 addresses to transport addresses. Because a zone is defined by its gatekeeper, H.323 entities that contain an internal gatekeeper require a mechanism to disable the internal function so that if there are multiple H.323 entities that contain a gatekeeper on a LAN, the entities can be configured into the same zone. Tables 1 and 2 shown below illustrate required and optional gatekeeper functions, respectively.
TABLE 1
Required Gatekeeper Functions
Address Translation
Translation of an alias address to a
transport address using a table that
is updated with registration messages.
Other methods of updating the
translation table are also allowed.
Admissions Control
Authorization of LAN access using
Admissions Request, Confirm and Reject
(ARQ/ARC/ARJ) messages. LAN access
can be based on call authorization,
bandwidth, or some other criteria.
Admissions Control can also be a null
function that admits all requests.
Bandwidth Control
Support for Bandwidth Request, Confirm
and Reject (BRQ/BCF/BRJ) messages.
This can be based on bandwidth
management. Bandwidth Control can
also be a null function which accepts
all requests for bandwidth changes.
Zone Management
The gatekeeper provides the above
functions for terminals, MCUs, and
gateways which have registered within
its zone of control.
TABLE 2
Optional Gatekeeper Functions
Call Control Signaling
In a point-to-point conference, the
gatekeeper can process Q.931 call
control signals. Alternatively, the
gatekeeper can send the endpoints'
G.931 signals directly to each other.
Call Authorization
The gatekeeper can reject a call from
a terminal based on the Q.931
specification. The reasons for
rejection can include, but are not
limited to, restricted access to/from
particular terminals or gateways,
restricted access during certain
periods of time. The criteria for
determining if authorization passes or
fails is outside the scope of H.323.
Bandwidth Management
The gatekeeper can reject calls from a
terminal if it determines that
sufficient bandwidth is not available.
This function also operates during an
active call if a terminal requests
additional bandwidth. The criteria
for determining if bandwidth is
available is outside the scope of
H.323.
Call Management
The gatekeeper can maintain a list of
ongoing H.323 calls in order to
indicate that a called terminal is
busy or to provide information for the
Bandwidth Management function.
Because gatekeepers execute on one or more physical machines, the processing ability of a gatekeeper is limited. In light of all of the important functions performed by a gatekeeper, it is preferable to define methods for controlling gatekeeper message processing and for preventing the gatekeeper from crashing during overload conditions. As used herein, the phrases “overload conditions” and “overload
Christie, IV Samuel H.
Li Xuewen
Nortel Networks Limited
Vu Viet D.
Withrow & Terranova , PLLC
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