INTRODUCTION:
A Telecommunication service provider provides different services to the users. Users use a variety of user terminals for accessing the services. Some of these services include connectivity to Internet, connectivity to external networks for voice connection, value added services such as streaming services. The streaming service includes the streaming of audio / video content or the streaming of any other such content. Existing networks employ a common architecture for any of these services. However, the service requirements for streaming service are very different from that of bursty Internet data service. Streaming service expects packets to be delivered to the user terminal with minimal network transfer latency and also a guaranteed bit rate. Besides, such services place a huge demand on the network bandwidth needed for the transfer of the streaming content. These characteristics imply that a general common network architecture for all the different services may not best satisfy the requirement of special services such as stored content transfer services. As such, there exists a need for defining network architectural elements that specifically cater to the requirement of the streaming service,
BACKGROUND OF INVENTION:
In any communication system, the network operator provides different services to the users. Users avail the services by connecting to the senyice specific sub¬system or service specific server or the service access gateway. A few examples of such services include Internet access, which is provided through an access gateway, operator specific services like content streaming provided through an appropriate content server and other value added services that are provided through service specific server. Within the scope of this invention, a content server provides access to stored audio/video or any other form of such stored content. Depending on the deployment scenario, there may also exist multiple instances of the content server.
Communications networks provide their services through an access network subsystem and a core network sub system. The access network provides functions specific to the access technology and provide a means for getting connected to the services offered by the core network. In the specific case of wireless access technologies, the access network provides functions such as establishment and release of radio channels, channel access procedures, power control and other such functions that are specific to the access technology. In case of 2.5G, 3G technologies, the access network comprises of the base station and the aggregation entities such as Base Station Controller (BSC), Radio Network Controller (RNC) respectively. Fig 1 indicates the manner in which a user terminal receives streaming content from a 3G network. In case of wired access technologies such as Digital Subscriber Line (DSL), the access network comprises of the aggregation entity such as a Digital Subscriber Line Access Multiplexer (DSLAM). The functions provided by the core network can be

considered to be fairly independent of the access technology. The core network infrastructure provides the connectivity to various services like Internet, operator specific services like content streaming. The other functions of the core network sub-system include authentication, service registration, mobility management, billing, interworking with external networks and other such similar functions that are independent of the access technology. In the particular case of Universal Mobile telecommunication System (UMTS) or 3G networks, the core network elements include Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN).
In order to use the operator provided services, such as retrieval of stored content, the user connects to the content server utilizing the services of the access and core network elements. A few examples of such stored content could be stored audio/video content. The user terminal establishes a data connection to the content server to fetch audio/video content. This connection can be established using various access link protocols and protocols within the core network. Once the connection is established, the content sender can deliver the content in different modes such as unicast, multicast In case of a multicast mode of content distribution, the user terminal would request to join the multicast group that serves the content.
Existing network architectures use the same data transfer path for transferring both time sensitive and bandwidth intensive huge content stored in the content server as well as the regular Internet traffic. Such network architecture will not be able to serve regular data traffic users efficiently, when several users are involved in retrieving content from the content server. Also, the existing data network architecture is not optimized for serving content when several users seek the stored content retrieval service. In order to provide service guarantees for services such as content retrieval service, existing networks attempt to over provision that results into wastage of bandwidth. Fig 1 is a representation of a given user terminal getting connected to a content server as per the existing 3G-network architecture. From this figure, it can be seen that the control signaling such as signaling for the setup/release of the data connection to the content server, signaling for requesting a particular content from the content server and any other such signaling, as well as the actual content transfer essentially happen over the same network infrastructure indicated in the figure. Also, the same transfer path indicated in the figure is used by both Internet traffic as well as streaming traffic from content server.
Patent WO2005/006121A2 highlights a ring overlay network for transferring content such as video content to a user's terminal. The suggested overlay method uses SONET ring topology for transferring content. As these SONET rings are pre-provisioned with certain fixed bandwidth, it results in under utilization of network bandwidth for packet-based services such as stored/live content transfer. Moreover, this work has restricted the scope of optimization for content transfer to the usage of a ring overlay network for content transfer. It

does not consider optimization techniques such as localized caching, reduction in the number of hops. Besides, it is also very specific to the DSL access technology and to the usage of DSLAM in the access network
SUMMARY OF THE INVENTION
In summary, embodiments of the present invention provide for a gigabit ethernet switch based overlay network that co-exists along with the legacy data network. The control signaling needed for setup/release of the connection with the Content Server (CS) and for requesting content and any other such signaling continues to be carried over the legacy data network 270, whereas, the Content Distribution Network (CDN) 300 is used for the actual data transfer. The invention also provides for a Content Distributor (CD) that can store content in its local cache. Method is provided for control information exchange between the Controller Function (CF) associated with CS and the CD. Upon command from the content server's controller function, the CD can serve content from its local cache. The unique aspect of this invention is the location of the content distributor within the access network and the manner in which it distributes content over an entire metro area from a single stored copy in the cache. As the cache distribution mechanism is purely confined to the access link, no communication with the backend IP network 360 is needed. In case content is not stored in the cache, it needs to be retrieved from the content server 400 over the backend IP network 360. Also, in the particular case of wireless access scenarios using 3G network, the usage of the CDN 300 for content transfer bypasses the normal data path of the corresponding legacy data network such as 2.5G or 3G network and provides for a direct connectivity between the CS and the corresponding Access Node (AN). As such, in case of wireless terminals, when content is actually to be fetched from the content sen/er rather than from the cache, the number of hops needed for retrieving content is also reduced.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
Fig 1 is an illustration of how a user terminal connected to an existing 3G network fetches content from a content server.
Fig 2 is a generalized representation of network architecture according to this invention.
Fig 3 illustrates how the CD's are connected via the gigabit Ethernet switch.
Fig 4 shows the data flow of a given user terminal and its associated interactions with the network for fetching content from the content server, according to the present invention.

Fig 5 shows the message flow in the particular case when the CD storing the content is different from the CD serving the user terminal.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS
Network architectural changes are provided for delivering live as well as stored content from a content server to the user's terminal. Embodiments of the present invention provide a system and method that can be used by devices connected to both wired as well as wireless access networks for retrieving content from the content server. User terminals connect via a communication network to a OS for the purpose of retrieving content. The communication network comprises of various entities such as the immediate access node, aggregating entities, and switching entities. In the particular case of wireless networks, the network would also comprise of entities to handle the terminal mobility.
Fig 2 is an embodiment of architecture according to this invention. As per Fig 2, the user terminals 100 represent a plurality of wired or wireless terminals. The user terminals 100 connect to the CS 400 using the corresponding wired or wireless access technology. A computing device connected to an internal or external DSL modem is an example of a terminal that employs DSL access technology to get connected to the network. Likewise, a mobile device or a PDA that employs WCDMA access technology for getting connected to the network is an example of a wireless user terminal. The user terminals and the corresponding access technologies listed here are used only to illustrate the idea of user terminals and the invention is not restricted to those user terminals or access technologies. The Access Nodes (AN's) 200 represents a plurality of access nodes to which the user terminals are connected. In any telecommunication network, the Access Node (AN) represents the entity to which the user terminal is directly connected either through a wired or wireless connection. In the case when the user terminal employs DSL as the access technology, a DSLAM would be the AN. In the case when WCDMA or WiMax is used as the access technology, the NodeB or the WiMax base station act as the respective access nodes. The AN could also represent eNodeB in case of LTE access technology. The invention brings out various optimization techniques within the network infrastructure elements for the purpose of transferring streaming media content and as such is not restricted to the use of any particular access technology.
Fig 2 shows the various elements of the CDN 300. The CDN 300 is an overlay network that co-exists with the legacy data network 250 for the purpose of content distribution. The various elements of the CDN 300 include a plurality of Content Distributors (CD's) 320, a Gigabit Ethernet Switch 340 and an IP network 360. Each CD is connected to a particular port of the Gigabit Ethernet Switch 340. The CS 400 shown in Fig 2 has storage associated with it for storing

the content that it serves to the individual user terminals upon request from the user terminals. The CS 400 also has a Controller Function (CF) 410 associated with it. The CF 410 is responsible for various control functions such as receiving the request for content from user terminal. The CDN 300 is an overlay network that is used only for transferring the streaming content from the CS 400. By transferring audio/video content and other such similar content over the CDN 300, the regular data traffic will not be affected when several users are retrieving content. In this way, the existing legacy network infrastructure can be used to serve the regular data traffic, whereas, content retrieval from the CS will be diverted over this overlay network.
As shown in Fig 2, embodiments of the present invention provide separate path for transfer of control signaling and the actual content transfer. The control signaling exchange needed for setting up / release of the connection to the CS 400 as well as the signaling with the CS 400 for requesting content and any other such signaling continues to be carried over the legacy data network 250 whereas the actual content transfer is carried over the CDN 300. The user terminal connects to the CS 400 over the legacy data network 250 and the IP network 270. This connection can be established using the protocols and procedures defined for the corresponding access technology. In the particular case of user terminals connecting using the WCDMA access technology, the terminal would use the various access and non-access stratum protocols for getting connected to the CS 400. The content can be transferred using either unicast or multicast modes of content transfer. In case content is transferred via multicast, the user terminals connection to the CS 400 would be a request to join the corresponding multicast group. In any case, during the connection establishment process, the CF 410 associated with CS 400 receives the identity of the AN serving the user terminal from the legacy data network 250. In case of wireless user terminals, the AN uses any technique such as paging to forward the content to the terminal. In case of terminals connected to wired network, the AN forwards the content over the interface port over which the terminal is connected to the AN.
As shown in Fig 3, the switch 340 has an interface to the IP router 362 of the IP network 360 besides interfaces to each of the CD's. Fig 3 also shows that each CD such as CD 322 has a local storage for storing the content transferred through that particular CD. This arrangement makes it possible for a given CD to transfer its stored content to another CD over the switch 340. The switch 340 has a MAC table 342 that maps the MAC address of the individual CD's to the corresponding switch port. This table gets dynamically updated as and when packets move across the switch 340.
Fig 4 gives a detailed flow of the complete sequence of actions involved when a user terminal connects to the CS 400 for retrieving live or stored content. As shown in Fig 4 and in block 152, the CF 410 associated with the CS 400 is provisioned with the MAC addresses of the individual CD's. Further, the CF 410 is also provisioned with a mapping table that indicates which CD is connected to

which AN. As already mentioned, during the process of establishing the connection with the CS 400, the CF 410 receives the identity of the AN serving the terminal from the legacy data network 250. With the provisioned information and with the information received from legacy data network 250, the CF 410 identifies the MAC address of the CD to which, the AN serving the user terminal is connected. So, whenever the terminal gets connected and requests for content, the CF 410 has all the needed information to route/switch the content directly to the corresponding AN which in turn serves the content to the user terminal.
Depending on whether content needs to be served from the storage associated with the CS 400 or from the storage associated with the CD's, and also depending on the CD that serves the terminal, three different ways of content transfer are possible. As shown by block 162 of Fig 4, when the terminal requests for content, the CF 410 checks whether the content is already available in the storage associated with any of the CD's. One particular way of content transfer is one wherein, this check detects that content is not available with any of the CD's which means that the CS 400 must transfer the content directly over the IP network 360 to the corresponding AN. In case of wireless terminals getting connected to the CS 400 over the legacy 3G network, usage of the legacy data network 250 for content transfer would mean that content is transferred over the SGSN and GGSN nodes as shown in Fig 1. For such cases, embodiment of this invention uses the CDN for content transfer and thus the SGSN and GGSN nodes are bypassed. This becomes possible mainly because this invention introduces a signaling between the legacy data network and the CF 410 for exchanging the terminal mobility information. As such, in case of terminal mobility, the CF 410 learns the identity of the AN currently serving the terminal and transfers the content to the corresponding AN,
At any time, when a particular CD is involved in the content transfer path for the first time, apart from transferring the content to a particular AN, it stores the content in its local storage or local cache. Further, each CD informs the CF 410 of the content that it has locally stored. In this manner, the CF 410 gets to know the content stored at each of the CD's such as CD 322. When a terminal requests for a particular content and the CF 410 finds that the content is already available with one of the CD's, it requests the particular CD to serve the content and passes to it the identity of the AN serving the user terminal. As this content transfer involves only the CD's and the AN, there is no transfer over the backend IP network 360 which improves the content transfer latency.
Fig 5 shows the third way of content transfer wherein the CD storing the content is different from the CD serving the terminal that requests for the content. In Fig 5. the path over which the terminal exchanges its control signaling for setting up / release of its data connection to the CS 400 and the subsequent request for content is marked as 301,302,303 and 304. When the CF 410 finds that content can be served from the storage associated with CD 324, it requests the CD 324

to transfer the content to the CD 322. This request is marked as 305,306 and 307. In this request, it passes the MAC address of the CD 322 to which the AN serving the user terminal is connected. Upon receiving this request, the CD 324 transfers the content over the path marked as 308,309 and 310. This kind of content transfer means that a single copy of stored content can serve an entire metro area served by a plurality of CD's. Further, this is a method for realizing localized content distribution purely using link specific technology such as ethernet switching without involving the IP network 360 that again results in a significant improvement in the content transfer latency.
As the legacy data network is left un-touched, no expensive upgrades of the same are needed. Also, deploying a gigabit Ethernet switch based solution would be cost effective compared to changing the legacy data network 250. The Gigabit Ethernet switch based overlay results in a packet-oriented overlay, which results in efficient bandwidth utilization for packet services such as content streaming. The Ethernet switch based content distribution would facilitate a faster and a convenient way for localized content distribution over a wide area such as a metro network without any involvement of backend IP network such as IP network 360. Content distribution can be achieved by link level Ethernet switching techniques, which improves the content transfer latency. The positioning of a cache based content distribution infrastructure within the access network facilitates faster content retrieval. By diverting the content related traffic onto the overlay network, the service provided to users who seek normal data traffic is not affected even when several users are fetching content from the content server. In the specific case of wireless terminals, when content is served from the storage associated with CS, usage of the CDN as defined within this invention results in reduction of the number of hops needed to serve the content and thus improving the content transfer latency
INDUSTRIAL APPLICABILITY:
1. Distribution of live or stored audio/video content over a metro area.
2. Point to point content transfer applications can also benefit from this architecture
3. Improves content transfer latency thereby yielding better content transfer performance for operator's
4. Efficient utilization of network bandwidth

Invention claims:
What is claimed is:
1. A system for distribution of stored or live content over a telecommunication network:
The telecommunication network comprising of a plurality of wired and wireless terminals, plurality of access nodes, CDN, legacy data network, IP network and a Content Server with its associated Controller function;
the CDN comprises of a plurality of CDs, a Gigabit Ethernet Switch, and IP network;
the CDs are interconnected by the Gigabit Ethernet switch and a plurality of access nodes connect to each CD;
the access nodes utilize any wired or wireless access technologies; and
the control signaling is carried over the legacy data network and the actual content is transferred over the CDN.
2. The system of claim 1 wherein, the CDN is an overlay network that co¬exists with the existing legacy data network;
CDN is used for both unicast and multicast mode of content transfer; and
CDN is capable of localized content distribution, without fetching content from the CS upon each request from the user terminal.
3. The system of claim 1 wherein, the CD is a common content distribution point for both wired as well as wireless terminals;
the CD is positioned within the access network;
CDs exchange control information relating to content distribution with the CF; and
each CD has an associated cache / storage.
4. A method for transferring content directly between the CS and the AN serving the user terminal, the method comprising:

provisioning the CF with the MAC addresses of each CD;
provisioning the CF with mapping information of each AN with the corresponding CD;
transferring the identity of the AN serving the user terminal between the legacy data network and the CF;
using the received serving AN identity information and the pre-provisoned information to identify and then to transfer content directly to the CD serving the user terminal;
transferring the AN identity to the CD; and
delivering content to the AN through the corresponding CD.
5. The method of claim 4 wherein, delivering the content locally without
involving the IP network for content distribution, the method comprising:
receiving, request from user terminal for content;
transferring, control information regarding stored content at each CD to the CS;
identifying, availability of the content with one of the CDs;
requesting, the identified CD to transfer the content to the CD serving the user terminal; and
transferring, a single stored copy of the content available at the identified CD to the CD serving the user terminal.
6. The method of claim 4 wherein, delivering the content locally without
involving the IP network and using a single identified CD for content
distribution, the method comprising:
receiving, request from user terminal for content;
transferring, control information regarding stored content at each CD to the CS;
identifying, availability of the content with one of the CD's;
requesting, the CD storing the content, to directly transfer the content to the AN, connected to it; and

transferring, content from CD to the corresponding AN.
7. The method of claim 4 wherein, delivering content is over the IP network, the method comprising:
receiving, request from user terminal for content stored at the CS;
transferring, control information regarding stored content at each CD to the CS;
identifying, non-availability of the content with any of the CD's; and
transferring content to the user terminal over the CDN.