GB2330035A

GB2330035A - A method and apparatus for managing sessions and resources in a video-on-demand system

Info

Publication number: GB2330035A
Application number: GB9814954A
Authority: GB
Inventors: Tae-Beom Lim
Original assignee: Daewoo Electronics Co Ltd
Current assignee: WiniaDaewoo Co Ltd
Priority date: 1997-09-30
Filing date: 1998-07-09
Publication date: 1999-04-07
Also published as: GB9814954D0

Abstract

The system comprises a plurality of users or clients 210 connected to a server 200 by an Asynchronous Transfer Mode (ATM) network. A user-to-user interface is provided for transmitting data between the user and a server, and a user-to-network interface is provided for transmitting and receiving data between the user or server and the network. The network includes a Session and Resource Manager (SRM) 230 whose function is to set up connections between the users and the server. Messages are received by the session manager and are inspected to determine whether they are valid. Valid messages are decoded and session information is sent to a state machine 2322 to setup a transaction. The state machine defines and event for the decoded message which may include setting up a session, assigning video channels and releasing the session. Events are only established when no other transaction is under way. The state machine updates the current state information and transmits this to the server or user via the ATM network. The system operates in accordance with the Digital Storage Media Command and Control (DSM-CC) protocol for transmitting MPEG data.

Description

METHOD AND APPARATUS FOR MANAGING SESSIONS AND RESOURCES IN A VIDEO-ON-DEMAND SYSTEM The present invention relates to a method and apparatus for managing sessions and resources at a network in a videoon-demand(VOD) system; and, more particularly, to a method and apparatus for managing the sessions and resources so that a multiplicity of users can access to the system in accordance with the Digital Storage Media Command and Control(DSM-CC) protocol.

A video-on-demand system serves to provide video information to a plurality of clients through various communication channels; and operates in conjunction with an information server for storing the video information and transmitting same to the clients and a communications network to transmit the information between the information server and the clients.

The DSM-CC protocol is a set of protocols which provides basic control functions and operations specific to managing MPEG data, e.g., video information, stored on various digital storage media at a local or a remote site. As shown in Fig.

1, such DSM-CC protocol may consist of two functional categories: user-to-user(UU) interface for transmitting and receiving data directly between a client user (client) and a server user(server); and user-to-network(UN) interface for transmitting and receiving data between the client or the server and the network. The UN interface has three subsystems: client, server and network, while the UU interface has only two subsystems: client and server, wherein the network is often referred to as a session and resource manager (SRM) because the SRM represents the DSM-CC functionality within the network.

The UN interface is in charge of a session setup event, a session release event and a resource request event, while the W interface is in charge of an intermediate process from an active state of the session to the generation of the resource request event and a transmission process for transmitting the MPEG data through the channel generated by the resource request. The session setup event for activating a session begins with the receipt of a Session Set Up Request from a user, i.e., a client or a server, and ends with the transmission of a Session Set Up Confirm to the user, wherein the Session~Set~Up~Request represents a message sent from the user to the network to set up the session, and the Session Set Up~Confirm represents a message sent from the network to the user in response to the Session~Set~Up~Request.

The session release event for releasing a session begins with the receipt of a Session Release Request from the user and ends with the transmission of a Session~Release~Confirm to the user1 wherein the Session Release~Request represents a message sent from a user to the network to release the session, and the Session~Release~Confirm represents a message sent from the network to the user in response to the Session~Release~Request. The resource request event for requiring an additional resource, e.g., to transmit the MPEG data, begins with the receipt of an Add~Resource~Request from the user and ends with the transmission of an Add~Resource~Confirm to the user, wherein the Add Resource Request represents a message sent from a user to the network asking for the additional resource, e.g., to transmit the MPEG data, and the Add~Resource~Confirm represents a message sent from the network to the user in response to the Add~Resource~Request.

In the video-on-demand system operated in the UU and the UN environments, the SRM of the UN environment is not designed to set up a new session by another user during the progress of a session. That is to say, since a request to set up another session by another user is not accepted during an activation interval, i.e., from the setup to the release, of a session, it is difficult for the conventional video-ondemand system to support a multiplicity of clients and a plurality of servers simultaneously.

It is, therefore, an object of the invention to provide a method and apparatus for managing sessions and resources in order that a multiplicity of users may access effectively to a video-on-demand system operated in accordance with a Digital Storage Media Command and Control(DSM-CC) protocol.

It is another object of the invention to provide a method and apparatus for managing session and resources in order that another user may access during an idle interval between two transactions of a user to the video-on-demand system.

According to the present invention there is provided an apparatus for managing sessions and resources in a video-on-demand system, which has at least a server of the UN interface("UN server") and at least a client of the UN interface("UN client") for communicating in an asynchronous transfer mode(ATM), the apparatus comprising: a session manager for managing the sessions; and a resource manager for assigning or releasing the resources by the state machine, wherein the session manager includes: a message decoder for decoding messages to produce decoded messages; a session information storage for storing current state information for each session; a state machine for establishing an event for the decoded message, only if no transaction is under way, based on the current state information, for performing a transaction for the event and for updating the current state information; and a message encoder for encoding the updated current state information and for transmitting the encoded message to a UN server or a UN client through an ATM network.

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: Fig. 1 illustrates a conventional video-on-demand system operated under the Digital Storage Media Command and Control (DSM-CC) protocol; Fig. 2 provides a block diagram of a video-on-demand system having a session and resource manager in a user-tonetwork environment in accordance with the present Invent Ion; Figs. 3A to 3C depict a flow chart for setting up a session, requiring a resource and releasing the session, respectively; and Figs. 4A and 4B show a flow chart for managing a session and resource in accordance with the present invention Referring to Fig. 2, there is shown a block diagram of a video-on-demand system on user-to-network environment, wherein the video-on-demand system for each session comprises a UN server 200 at a server, a UN client 210 at a client, a session and resource manager(SRM) 230 at a network and an ATM switch 220, wherein the SRM 230 is for setting up a session, assigning a resource and releasing a session between the UN client 210 and the UN server 200 and the ATM switch 220 is for connecting the UN server 200 and/or the UN client 210 to the SRM 230 for the data communication therebetween.

Any of the UN server 200 and the UN client 210 has a user session manager, a user configuration manager and a user resource manager in order to carry out the function of the server or the client in the UN environment.

The SRM 230 includes an ATM network card 231, a session manager 232 and a resource manager 233, wherein the ATM network card 231 is for interfacing the SRM 230 with the ATM switch 220 in order to receive and transmit data, the session manager 232 is for controlling the whole function of the SRM 230 and the resource manager 233 controlled by the session manager 232 is for transmitting to the ATM network card 231 information to assign and to release the resources.

Specifically, the ATM network card 231 receives data from the UN server 200 or the UN client 210 through the ATM switch 220 and transmits information from the SRM 230 through the ATM switch 220 to a corresponding UN server 200 or UN client 210.

The session manager 232 has a message decoder 2321, a state machine 2322, a session information storage 2323 and a message encoder 2324 and controls the whole functions of the SRM 230.

First, the message decoder 2321 determines whether a message transmitted from the ATM network card 231 is valid by inspecting a header thereof and, only if the message is valid, decodes the message according to a predetermined protocol to provide decoded massage to the state machine 2322.

That is to say, the message decoder 2321 inspects a Protocol~Discriminator and a dsmccType in the header of the message so as to determine whether or not the message accords with the UN environment, wherein the Protocol Discriminator indicates whether or not the message corresponds to a DSM-CC message which conforms to the DSM-CC protocol and the dsmcc~Type indicates whether the message is used in either a DSM-CC UU environment or a DSM-CC UN environment. The DSM-CC UU environment represents a communication between a client of the UU interf ace ( " UU client") and a server of the UU interface("W server") and the DSM-CC UN environment represents a communication either between a UN client and a UN SRM entity or between a UN server and a UN SRM entity. If the message conforms to the DSM-CC UN protocol, the message decoder 2321 determines whether the message is transmitted from either the UN server or the UN client by analyzing a message identifier(message~Id) of the header of the message and decodes the message based on the determination results.

The decoded message is coupled with the state machine 2322.

The state machine 2322 defines an event for the decoded message fed from the message decoder 2321 based on session information, i.e., state information of a session, stored in the session information storage 2323 and, then, carries out a transaction for the event, wherein the transaction includes an event for setting up a session, an event of assigning an MPEG channel to transmit MPEG data on the session and an event for releasing the session. After the transaction, the result will be stored in the session information storage 2323 as session information for a next event.

Referring to Figs. 3A to 3C, there are illustrated exemplary processes for managing a session in the state machine 2322 based on the message from one of the users, i.e., a UN client, wherein Figs. 3A to 3C correspond to transactions for setting up a session, establishing a motion picture export group(MPEG) channel for the session and releasing the session, respectively.

If a message of Client~Session Set Up Request is provided from the UN client 210, the state machine 2322 establishes an event for setting up a session based on the state information from the session information storage 2323. That is, based on a server identifier(server Id) fed with the message of Client~Session~Set Up~Request, the state machine 2322 makes the message encoder 2324 encode a message of Server~Session~Set~Up~Indication to be transmitted to the UN server 200.

As shown in Fig. 3B, if a message of Server~Add Resource Request for the session is transmitted through the message decoder 2321 from the UN server 200 based on the message of Sewer~Session~Set Up Indication, the state machine 2322 of the network makes the message encoder encode a message of Server Add Resource~Confirm to be transmitted to the server 200 and, then, controls the resource manager 233 to assign the resources required to the UN server 200.

Referring back to Fig. 3A, if a message of Server~Session~Set~Up~Response is transmitted through the message decoder 2321 from the UN server 200 to which the resources are assigned, the state machine 2322 makes the message encoder 2324 encode a message of Client Session Set Up Confirm to be transmitted to the UN client 210. The state machine 2322 makes the session information storage 2323 store a session information indicating the session is in an active state.

A flag of the session information at the session information storage 2323 maintains an active state from the setup of the session till the release thereof, because any client-server pair can communicate with each other on a session-by-session basis. Since the session information is updated for each transaction, the session information is updated as soon as a session setup event for setting up the session as shown in Fig. 3A, a channel setup event for establishing the MPEG channel as shown in Fig. 3B, or a session release event for releasing the session as shown in Fig. 3C is completed.

The session information for each session includes Current~State, session~Id, Client address, Server~address and flag. The Current State is a state value of the current session updated for each transaction. Since each message is always transmitted with a corresponding session Id, the session Id is unique to each session so that the state machine 2322 can detect the session information in the session information storage 2323 based on the session~Id. The Client~address and the Server~address are addresses of the client and the server connected to the session, respectively.

The flag '1' or '0' indicates whether the session is in use or not, 'I' and '0' representing in use and out of use, respectively, so that the flag '1' is established from the setup of the session to the release thereof. As a result, the session information storage 2323 stores the session information on a session-by-session basis for all sessions within the SRM 230.

The message encoder 2324 encodes the message fed from the state machine 2322 and provides the encoded message to the ATM network card 231.

The resource manager 233 is controlled by the state machine 2322 and transmits a signal to assign the resources required for the session to the UN client 210 or another signal to release the assigned resources in accordance with the session release event. As shown in Fig. 3B, if the message of Server~Add~Resource~Request is transmitted from the UN server 200 to the network, the state machine 2322 controls the resource manager 233 to transmit resource information for the session to the ATM network card 231 so that, upon the receipt of the message of Client~Add~Resource~Indication, the resources are assigned to the UN server 200. As shown in Fig.

3C, if a message of Session~Release~Request is transmitted from the client UN, a release information for the resource which must be released is transmitted to the ATM network card 231 in order that the resource assigned by the state machine 2322 will be controlled to be released.

Referring to Figs. 4A and 4B, there is shown a flow chart illustrating an aspect of the present invention regarding the process of managing the session and the resource. First of all, at step S401, a message is received from the ATM network card 231 and, at step S402, the message decoder 2321 determines the validity of the message by checking whether or not the message conforms to the DSM-CC protocol by inspecting a Protocol~Discriminator of the header thereof, wherein the Protocol~Discriminator indicates whether the message conforms to the DSM-CC protocol or not.

If the Protocol~Discriminator is not valid, i.e., the message does not conform to the DSM-CC protocol, at step S403, the message is considered to be in error and returning to step S401, wherein another message is received. If the Protocol~Discriminator is valid, at step S404, the SRM determines whether or not a dsmcc~Type in the header of the message is valid, i.e., the message corresponds to the UN environment, wherein the dsmcc~Type indicates whether the message corresponds to the UN or the UU environment.

If the dsmcc~Type is not valid, at step S403, the message is determined to be in error and returning to step S401; and if otherwise, at step S405, it is checked if the message corresponds to a new session by inspecting a message identifier(message within the header of the message. If the message~Id, e.g., '0x4010' or '0x8010', for requesting a session is transmitted from the client UN or the server UN, it is decided that the message corresponds to a new session.

If the message corresponds to the new session, i.e., the message Id is either '0x4010' or '0x8010', at step S405-1, a new process for the new session is forked and, if otherwise, at step S405-2, the message is transferred to a corresponding process.

Thereafter, at steps S406 and S407, it is determined whether the message is transmitted from either the UN client 210 or the UN server 200 by inspecting the message~Id in the header of the message.

If the message is transmitted from neither the UN client 210 nor the UN server 200, at step S403, the message is considered to be in error and return to step S401; and if the message is transmitted from either the UN client 210 or the UN server 200, at step S408, the state machine 2322 checks whether a transaction is under way. If the transaction is under way, at step S409, the state machine 2322 will be on standby so as not to receive the decoded message from the message decoder 2321 until the transaction is finished.

If the transaction is finished so that no transaction at the state machine 2322 proceeds, at step S410, the state machine 2322 receives the decoded message and, at step S412, sets up an event based on the -Current~State of the session stored in the session information storage 2323. If the decoded message corresponds to the Session~Set~Up~Request as shown in Fig. 3A, the Current~State will maintain 'don't care' and the flag will be '0' so that, at step S412, the state machine 2322 will establish an event for setting up a session.

If the decoded message is the Add~Resource~Request as shown in Fig. 3B, the Current~State represents the active state of the session so that the state machine 2322 will establish another event for further assigning resources for the session.

After setting up the event, at step 413, the state machine 2322 performs a transaction for each event until a last message of the transaction is received, wherein each last message has the suffix 'Response' . It is impossible for another user to have an access to the state machine 2322 during the transaction. At step S414, if the last message of the transaction has been received, at state S415, the session information stored in the session information storage 2333 is updated and, at step 416, a message is encoded by the message encoder 2324 to be transmitted and the encoded message is provided to the ATM network card 231. If it is determined at step S414 that the last message of the transaction is not received, then it returns to step S413.

At step S417, it is checked if the corresponding session is released. If the client UN and the server UN transmit a message of Release~Request for the corresponding session and the state machine 2322 of the SRM 232 provides a message of Release~Confirm, the session is determined to be released.

If the session is not released, at step S401, the SRM maintains on standby so that the messages for performing the next transaction of the session, setting up another new session, or performing another transaction of the new session will be received and, if otherwise, at step S418, the session is released.

As described above, information on a session is updated on a transaction-by-transaction basis so that, even if no transaction of the session is under way, another transaction of a new or another session can be performed.

While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

Claims

Claims 1. An apparatus for managing sessions and resources in a video-on-demand system, which has at least a server of the UN interface("UN server") and at least a client of the UN interface(??UN client??) for communicating in an asynchronous transfer mode(ATM), the apparatus comprising: a session manager for managing the sessions; and a resource manager for assigning or releasing the resources by the state machine, wherein the session manager includes: a message decoder for decoding messages to produce decoded messages; a session information storage for storing current state information for each session; a state machine for establishing an event for the decoded message, only if no transaction is under way, based on the current state information, for performing a transaction for the event and for updating the current state information; and a message encoder for encoding the updated current state information and for transmitting the encoded message to a UN server or a UN client through an ATM network.
2. The apparatus as recited in claim 1, wherein the session information storage stores Current~State information to indicate a current state for said each session, session~ID information for identifying said each session, client~address, server~address and flag information for indicating whether said each session is in use or not.
3. A method for managing sessions and resources in a videoon-demand system, which has at least a server of the UN interface("UN server") and at least a client of the UN interface("UN client") for communicating in an asynchronous transfer mode(ATM), the method comprising the steps of: (a) receiving a message from either a UN server or a UN client; (b) inspecting a header of the message to thereby determine whether or not the message is valid; (c) only if the message is valid, decoding the message to generate a session information; (d) checking whether or not there is a transaction under way; (e) only if no transaction is under way, establishing an event based on the session information; (f) performing a transaction based on the event until a last message of the transaction has been received; and (g) if the last message of the transaction has been received, updating the session information based on the last message.
4. A method according to claim 3, wherein the session information includes Current~State information for indicating a current state for said each session, session~ID information for identifying said each session and flag information for indicating whether said each session is in use or not.
5. A method according to claim 4, wherein the step (b) includes the steps of: (bl) determining whether the message conforms to a DSM-CC protocol based on a Protocol~Discriminator signal within the header thereof; and (b2) if the message conforms to the DSM-CC protocol, deciding whether the message corresponds to a user-to-network environment or a user-to-user environment based on a dsmcc~Type signal within the header thereof.
6. A method according to claim 5, wherein the step (b) further includes, after the step (b2), the steps of: (b3) determining whether the message is for a new session based on a message identifier within the header thereof; and (b4) if the message is for the new processing, forking a new process for the new session.
7. An apparatus constructed and arranged substantially as herein described with reference to or as shown in Figures 2 to 4 of the accompanying drawings.
8. A method substantially as herein described with reference to or as shown in Figures 2 to 4 of the accompanying drawings.