(51) Int Cl.: H04L 29/12 ( )

Transcription

1 (19) (11) EP B1 (12) EUROPEAN PATENT SPECIFICATION (4) Date of publication and mention of the grant of the patent: Bulletin 08/49 (21) Application number: (22) Date of filing: (1) Int Cl.: H04L 29/12 (06.01) (86) International application number: PCT/US01/0241 (87) International publication number: WO 02/02803 ( Gazette 02/12) (4) SPEED SENSITIVE CONTENT DELIVERY IN A CLIENT-SERVER NETWORK GESCHWINDIGKEITSABHÄNGIGE INHALTSLIEFERUNG IN EINEM CLIENT-SERVER NETZWERK LIVRAISON ACCELEREE DE CONTENU SENSIBLE DANS UN RESEAU SERVEUR-CLIENT (84) Designated Contracting States: DE FR GB () Priority: US (43) Date of publication of application: Bulletin 03/28 (73) Proprietor: Intel Corporation Santa Clara, CA 902 (US) (72) Inventors: JARDIN, Cary, A. San Diego, CA (US) VARSANYI, Eric Plymouth, MN 441 (US) DUCLOS, Phil, J. Longmont, CO 8004 (US) PADUA, Vincent, M. San Diego, CA (US) TRESCOTT, Robert, C., Jr. San Diego, CA (US) (74) Representative: Loveless, Ian Mark Reddie & Grose 16 Theobalds Road London WC1X 8PL (GB) (6) References cited: EP-A EP-A US-A US-A CARDELLINI V ET AL: "Dynamic Load Balancing in Web-Server Systems" IEEE INTERNET COMPUTING, May 1999 (1999-0), XP BICKMORE T W ET AL: "Digestor: deviceindependent access to the World Wide Web" COMPUTER NETWORKS AND ISDN SYSTEMS, NORTH HOLLAND PUBLISHING. AMSTERDAM, NL, vol. 29, no. 8-13, 1 September 1997 ( ), pages 7-82, XP009 ISSN: EP B1 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). Printed by Jouve, 7001 PARIS (FR)

2 1 EP B1 2 Description TECHNICAL FIELD [0001] This invention relates to measured data flow, and more particularly to connecting a client to a particular destination based on the connection speed of the client. [0002] To provide greater access to the Internet, the communication protocols and languages utilized by the clients and servers have become standardized. These protocols include the Hyper-Text Transfer Protocol (HT- TP), which is the communication protocol used for communications between clients and servers, and the Transfer Control Protocol/Internet Protocol (TCP/IP). The TCP portion is the transport-specific protocol for communication between computers or applications. IP is a lowerlevel protocol than TCP and facilitates the transmission of data packets between remotely-located machines. TCP is a transport-level protocol that operates on top of IP. TCP provides a full-duplex byte stream between applications, whether they reside on the same machine or on remotely-located machines. TCP ensures that transmitted data packets are received in the same order in which they were transmitted. [0003] Remote terminals or computers may connect to the Internet via an Internet Service Provider (ISP) using a variety of connection methods and speeds. These may include, among other things, a dial-up modem at 28.8 kilobits per second (Kbps), dial-up at 6 Kpbs, an Integrated Services Digital Network (ISDN) line, a Digital Subscriber Line (DSL), a cable modem, or a T1 line. Although each of these methods allow for connection to the Internet, each method does so at differing speeds. For example, a typical dial-up modem connects to the Internet at 6 Kbps while a T1 line may connect at 1.44 million bits per seconds (Mbps). The increased bandwidth of the higher speed connections allows more information to be downloaded in a shorter period of time. [0004] Web designers are taking advantage of the proliferation of high bandwidth connections to the Internet by creating more content rich websites. This allows more information, multimedia, and features to be provided to the users. However, for users that are connecting to the Internet using a slower speed connection, these highcontent websites take an exceedingly long period of time to load. Many users allow a limited period of time for a website to download. If a website is not fully downloaded within this limited time period, the user typically logs off the Internet or proceeds to another website. Thus, webdesigners are forced to decide between providing content rich sites for the high-bandwidth connections and losing the low-bandwidth connections or decreasing the amount of information provided to everyone. [000] US discloses a distributed directory for enhanced network communication in which the dependence upon a centralized repository of information is reduced by distributing directory information. US discloses a system for responding to a resource request using a domain name service server, which provides load balancing amongst a plurality of servers. DESCRIPTION OF DRAWINGS BACKGROUND [0006] These and other features and advantages of the invention will become more apparent upon reading the following detailed description and upon reference to the accompanying drawings. Figure 1 is a block diagram of a network server connection using a client interface device according to an embodiment of the present invention. Figure 2 illustrates a destination address including a plurality of sub-addresses optimized for specific connection speeds according to an embodiment of the present invention. Figure 3 is a diagram of the exchange between the client, the client interface device, and the server according to one embodiment of the present invention. Figure 4 is a flow chart of the process used by the client interface device to optimize the connection between the client and the server according to an embodiment of the present invention. DETAILED DESCRIPTION [0007] Figure 1 is a block diagram of a network server connection 0 using a client interface device 1 according to an embodiment of the present invention. A client communicates with the client interface device 1. The client may be a remote computer connected to a network such as a local area network, a wide area network, the Internet, or the like. For purposes of illustration, the invention will be described herein with a connection to the Internet. The client interface device 1 communicates with the server 11. The client interface device 1 relays information from the client to the server 11 in both directions. The client interface device 1 may also directly connect the client to the server 11. [0008] Figure 2 illustrates a destination group 0 including a destination address and a plurality of subaddresses 2-22 optimized for specific connection speeds. Web designers are continually placing more and more information on a web page. This allows the web designers to increase the amount of information delivered to the client, and also allows for the creation of a more entertaining website using streaming video, music, and large graphic files. Those clients connecting to the server 11 with a high bandwidth connection can enjoy the full features of the website. [0009] The destination address may be designed for optimal viewing by a client connecting to the server 11 using a connection having 1. Mbps or higher. 2

3 3 EP B1 4 With this connection speed, the client is able to view all of the content of the destination address without undue delays caused by downloading. However, if a slower speed client attempted to connect to the high bandwidth designed destination address, the client would require a large amount of time to load the contents of the page. This would result in longer delays and a reduction in the quality of service provided the client. Therefore, web designers may create sub-addresses which are designed for slower speed connections. A first sub-address 2 may be designed for clients connecting at 28.8 Kbps, a second sub-address 21 may be designed for clients connecting at 6.6 Kbps, a third subaddress 2 may be designed for clients connecting at 128 Kbps, and a fourth sub-address 22 may be designed for clients connecting at 12 Kbps. Of course, the number of sub-address may vary site to site. Each of the sub-addresses 2-22 includes a reduced amount of content to allow the site to load within an acceptable period of time under the designated connection speed. To achieve this, the sub-address 2-22 may remove some multimedia content, use reduced resolution, delete some content, or other techniques to reduce the bandwidth necessary. If the destination address is a graphics file, the sub-address 2-22 may be the same graphics file at respectively lower resolutions. The location of the sub-addresses 2-22 may be provided to a client or client interface device 1 attempted to access the destination address. [00] Figure 3 is a diagram of the exchange between the client, the client interface device 1, and the server 11 according to one embodiment of the present invention. To initiate a connection to the server 11, the client requests a connection by transmitting a SYN packet. Although the client is sending the SYN packet to the server 11, the SYN packet will be received by the client interface device 1. The client interface device 1 then responds to the client with a SYN/ACK packet 3. The client interface device begins timing upon transmission of the SYN/ACK packet 3. After receiving the SYN/ACK packet 3, the client responds with an ACK 31 back to the client interface device 1. Once the ACK 31 is received, the client interface device 1 stops timing and calculates the elapsed time required for the communication to the client. Based on this elapsed time, the client interface device 1 is able to determine a profile for the client. The profile may include the data flow rate. Several factors may affect the profile of the client, including the connection speed and network congestion. [0011] Once the client has successfully established a connection, the client may issue a GET request 3 to the server 11. The GET request 3 may be requesting a website, a file, or other destination. Once received, the client interface device 1 acknowledges the GET request 3 with an ACK 32 signal. [0012] To complete the GET request 3, the client interface device 1 establishes a connection with the server 11. The client interface device 1 establishes the connection by transmitting a SYN packet 3 to the server 11. The server 11 receives the SYN packet 3 and responds with a SYN/ACK packet 33. After receiving the SYN/ACK packet 33, the client interface device 1 responds with an ACK 3 back to the server 11. [0013] Now that the connection to the server 11 is established, the client interface device 1 examines the GET request 3 and determine if the client can successfully complete this request in the necessary time frame. The client interface device 1 uses the client profile to determine the timing requirements. The client interface device 1 then creates a GET request based of the GET request 3 of the client and the calculated client profile. If the client is able to handle the original GET request 3, the client interface device 1 will simply forward that as the GET request 34 which is sent to the server 11. However, if the client cannot handle the original GET request 3, the client interface device will determine a revised GET request 34 based on the client profile. For example, the original GET request may be for the destination address, but the client may only have a 128 Kbps profile. In this circumstance, the client interface device 1 will rewrite the request to send the client to the sub-address 2. Thus, the GET request 34 sent to the server 11 will be for the sub-address 2. When the server 11 receives the GET request 34, the server 11 sends an ACK to acknowledge the request. [0014] After the server 11 receives the GET request 34, normal TCP/IP and HTTP protocols facilitate client request fulfillment. During this process, the client interface device 1 may create a more detailed profile of the client connection speed. Of course, the client interface device 1 may also directly connect the client to the server 11. [001] Figure 4 is a flow chart of the process 0 used by the client interface device 1 to optimize the connection between the client and the server 11 according to an embodiment of the present invention. The process 0 begins in START block. Proceeding to block 4, the client interface device 1 determines the response time of the client. This allows the client interface device 1 to estimate a connection speed of the client. [0016] Proceeding to block 41, the client interface device 1 receives a resource request from the client. The resource request may be for a website, a file, or other data to be transferred to the client. The process 0 then proceeds to block 4. In block 4, the client interface device 1 determines if the resource request can be fulfilled based on the measured response time of the client. If the request can be fulfilled, the process 0 proceeds along the YES branch to block 42. In block 42, the resource request is transmitted to the server 11. [0017] Returning to block 4, if the resource request cannot be fulfilled, the process 0 proceeds along the NO branch to block 4. In block 4, the client interface 3

4 EP B1 6 device rewrites the resource request to optimize the client loading based on the measured response time. For example, a client may request a website which is optimized for connection using 1. Mbps. However, the measured response time may indicate the client has a response time of 6 Kbps. In this case, the client interface device 1 may rewrite the request to which is the same website content optimized for 6 Kbps. [0018] After the request or rewritten request is sent to the server 11, the process 0 proceeds to block 43. In block 43, the client interface device 1 connects the server 11 to the client. During the connection, the client interface device 1 may act as a conduit, continually measuring the client response time or may directly connect the server 11 to the client. The process 0 then terminates in END block 4. Claims 1. A method of enhancing data delivery comprising: sending a first packet (3) from a client interface (1) to a remote terminal () at a first time; receiving at the client interface a second packet (31) from the remote terminal at a second time; determining a response time of the remote terminal () at the client interface (1) based on a time period elapsing between the first time and the second time; using said response time to estimate a connection speed between the remote terminal () and the client interface (1); providing a plurality of destination addresses (2-22), said destination addresses relating to different amounts of content at a server (11) coupled to the client interface, each destination address being optimized for a specific connection speed; based on said measured response time, selecting a destination address from said plurality of destination addresses (2-22), said selected destination address being optimized for said determined connection speed; and connecting the remote terminal () to the selected destination address. 2. The method of Claim 1, further comprising determining a data flow rate from the determined response time of the remote terminal (), wherein determining the response time comprises: starting a timer at the first time when the client interface (1) sends the first packet to the remote terminal (); and stopping the timer at the second time when the client interface (1) receives the second acknowledgement packet from the remote terminal (). 3. The method of Claim 1, further comprising determining the response time by monitoring a latency in the TCP protocols. 4. The method of Claim 1, further comprising determining the network congestion based on the determined response time.. The method of Claim 1, further comprising determining the response time based on the timing of a handshake between the remote terminal () and the client interface (1). 6. The method of Claim 1, wherein selecting the destination address from a plurality of addresses is based on a requested address by the remote terminal () and the determined response time. 7. The method of claim 1, wherein selecting the destination address is performed automatically. 8. The method of Claim 7, further comprising determining a data flow rate from the remote terminal () based on the response time. 9. The method of Claim 7, wherein the destination address includes a main destination address and a plurality of sub-addresses, each of said sub-addresses corresponding to a connection speed and optimized for said connection speed.. The method of Claim 7, further comprising determining a network congestion based on the determined response time. 11. A system comprising a client interface (1), for use with a remote terminal () and a server (11), including instructions residing on a machine-readable storage medium, the instructions causing the system to: send a first packet from the client interface (1) to a remote terminal (); receive at the client interface a second packet from the remote terminal; determine a response time of the remote terminal at the client interface based on a time period between the first packet being sent and the second packet being received; use said response time to estimate a connection speed between the remote terminal and the client interface; provide a plurality of destination addresses, said destination addresses relating to different 4

5 7 EP B1 8 amounts of content at a server (11) coupled to the client interface, each destination address being optimized for a specific connection speed; receive a request for a destination address; based on said measured response time, select a destination address corresponding to the request; and communicate the selected destination address to the remote terminal. 12. The system of Claim 11, wherein the instructions further cause the system to connect the remote terminal () to the selected destination address. mit verschiedenen Mengen von Inhalt an einem an die Client-Schnittstelle gekoppelten Server (11) zusammenhängen, wobei jede Zieladresse für eine bestimmte Verbindungsgeschwindigkeit optimiert ist; Wählen, basierend auf der genannten gemessenen Antwortzeit, einer Zieladresse aus der genannten Vielzahl von Zieladressen (2-22), wobei die genannte gewählte Zieladresse für die genannte bestimmte Verbindungsgeschwindigkeit optimiert ist; und Verbinden des abgesetzten Endgeräts () mit der gewählten Zieladresse. 13. The system of Claim 11, wherein the response time is affected by network congestion. 14. The system of Claim 11, wherein the response time is determined based on the timing of a handshake between the remote terminal () and the client interface. 1. The method of Claim 1, further comprising: receiving a request from the remote terminal () for a destination address at the server (11); and rewriting the request to include the selected destination address optimized for the determined connection speed of the remote terminal (). 16. The method of Claim 1, wherein selecting the destination address is performed responsive to a request received. Patentansprüche 1. Verfahren der Verbesserung von Datenlieferung das Folgendes umfasst: Senden eines ersten Pakets (3) von einer Client-Schnittstelle (1) zu einem abgesetzten Endgerät () zu einer ersten Zeit; Empfangen an der Client-Schnittstelle eines zweiten Pakets (31) vom abgesetzten Endgerät zu einer zweiten Zeit; Bestimmen einer Antwortzeit des abgesetzten Endgeräts () an der Client-Schnittstelle (1) basierend auf einer zwischen der ersten Zeit und der zweiten Zeit verstreichenden Zeitperiode; Verwenden der genannten Antwortzeit, um eine Verbindungsgeschwindigkeit zwischen dem abgesetzten Endgerät () und der Client- Schnittstelle (1) abzuschätzen; Bereitstellen einer Vielzahl von Zieladressen (2-22), wobei die genannten Zieladressen Verfahren nach Anspruch 1, weiter umfassend das Bestimmen einer Datenflussrate aus der bestimmten Antwortzeit des abgesetzten Endgeräts (), wobei das Bestimmen der Antwortzeit Folgendes umfasst: Starten eines Zeitmessers zu der ersten Zeit, wenn die Client-Schnittstelle (1) das erste Paket an das abgesetzte Endgerät () sendet; und Anhalten des Zeitmessers zu der zweiten Zeit, wenn die Client-Schnittstelle (1) das zweite Quittierungspaket vom abgesetzten Endgerät () empfängt. 3. Verfahren nach Anspruch 1, weiter umfassend das Bestimmen der Antwortzeit durch Überwachen einer Latenzzeit in den TCP-Protokollen. 4. Verfahren nach Anspruch 1, weiter umfassend das Bestimmen der Netzüberlastung basierend auf der bestimmten Antwortzeit.. Verfahren nach Anspruch 1, weiter umfassend das Bestimmen der Antwortzeit basierend auf der Zeitmessung eines Quittungsaustauschs zwischen dem abgesetzten Endgerät () und der Client-Schnittstelle (1). 6. Verfahren nach Anspruch 1, wobei das Wählen der Zieladresse aus einer Vielzahl von Adressen auf einer angeforderten Adresse durch das abgesetzte Endgerät () und die bestimmte Antwortzeit basiert ist. 7. Verfahren nach Anspruch 1, wobei das Wählen der Zieladresse automatisch erfolgt. 8. Verfahren nach Anspruch 7, weiter umfassend das Bestimmen einer Datenflussrate von dem abgesetzten Endgerät () basierend auf der Antwortzeit. 9. Verfahren nach Anspruch 7, wobei die Zieladresse eine Hauptzieladresse und eine Vielzahl von Unter-

6 9 EP B1 adressen umfasst, wobei die genannten Unteradressen jeweils einer Verbindungsgeschwindigkeit entsprechen und für die genannte Verbindungsgeschwindigkeit optimiert sind.. Verfahren nach Anspruch 7, weiter umfassend das Bestimmen einer Netzüberlastung basierend auf der bestimmen Antwortzeit. 11. System, umfassend eine Client-Schnittstelle (1), für die Verwendung mit einem abgesetzten Endgerät () und einem Server (11), umfassend auf einem maschinenlesbaren Speichermedium residierende Anweisungen, wobei die Anweisungen das System veranlassen: 1 1. Verfahren nach Anspruch 1, das weiter Folgendes umfasst: Empfangen einer Anforderung vom abgesetzten Endgerät () für eine Zieladresse am Server (11); und Neuschreiben der Anforderung, um die gewählte Zieladresse, die für die bestimmte Verbindungsgeschwindigkeit des abgesetzten Endgeräts () optimiert ist, einzuschließen. 16. Verfahren nach Anspruch 1, wobei das Wählen der Zieladresse ansprechend auf eine empfangene Anforderung erfolgt. ein erstes Paket von der Client-Schnittstelle (1) zu einem abgesetzten Endgerät () zu senden; an der Client-Schnittstelle ein zweites Paket von dem abgesetzten Endgerät zu empfangen; eine Antwortzeit des abgesetzten Endgeräts an der Client-Schnittstelle basierend auf einer Zeitperiode zwischen dem Senden des ersten Pakets und dem Empfangen des zweiten Pakets zu bestimmen; die genannten Antwortzeit dazu zu verwenden, eine Verbindungsgeschwindigkeit zwischen dem abgesetzten Endgerät und der Client- Schnittstelle abzuschätzen; eine Vielzahl von Zieladressen bereitzustellen, wobei die genannten Zieladressen mit verschiedenen Mengen von Inhalt an einem an die Client-Schnittstelle gekoppelten Server (11) zusammenhängen, wobei jede Zieladresse für eine bestimmte Verbindungsgeschwindigkeit optimiert ist; eine Anforderung für eine Zieladresse zu empfangen; basierend auf der genannten gemessenen Antwortzeit eine der Anforderung entsprechende Zieladresse zu wählen; und die gewählte Zieladresse an das abgesetzte Endgerät zu kommunizieren. 12. System nach Anspruch 11, wobei die Anweisungen des Weiteren das System veranlassen, das abgesetzte Endgerät () mit der gewählten Zieladresse zu verbinden. 13. System nach Anspruch 11, wobei die sich Netzüberlastung auf die Antwortzeit auswirkt. 14. System nach Anspruch 11, wobei die Antwortzeit basierend auf der Zeitmessung eines Quittungsaustauschs zwischen dem abgesetzten Endgerät () und der Client-Schnittstelle (1) bestimmt wird Revendications 1. Procédé pour améliorer la livraison de données consistant à : envoyer un premier paquet (3) depuis une interface client (1) jusqu à un terminal distant () à un premier instant ; recevoir au niveau de l interface client un deuxième paquet (31) provenant du terminal distant à un deuxième instant ; déterminer un temps de réponse du terminal distant () au niveau de l interface client (1) sur la base d une période de temps s écoulant entre le premier instant et le deuxième instant ; utiliser ledit temps de réponse pour estimer une vitesse de connexion entre le terminal distant () et l interface client (1) ; fournir une pluralité d adresses de destination (2-22), lesdites adresses de destination se rapportant à différentes quantités de contenu au niveau d un serveur (11) couplé à l interface client, chaque adresse de destination étant optimisée pour une vitesse de connexion spécifique ; sur la base dudit temps de réponse mesuré, sélectionner une adresse de destination à partir de ladite pluralité d adresses de destination (2-22), ladite adresse de destination sélectionnée étant optimisée pour ladite vitesse de connexion déterminée ; et connecter le terminal distant () à l adresse de destination sélectionnée. 2. Procédé selon la revendication 1, consistant en outre à déterminer un débit de données à partir du temps de réponse déterminé du terminal distant (), dans lequel la détermination du temps de réponse consiste à : mettre en route un temporisateur au premier instant auquel l interface client (1) envoie le pre- 6

7 11 EP B1 12 mier paquet au terminal distant () ; et arrêter le temporisateur au deuxième instant auquel l interface client (1) reçoit le deuxième paquet d accusé de réception provenant du terminal distant (). 3. Procédé selon la revendication 1, consistant en outre à déterminer le temps de réponse en surveillant un temps d attente dans les protocoles TCP. 4. Procédé selon la revendication 1, consistant en outre à déterminer l encombrement sur le réseau sur la base du temps de réponse déterminé.. Procédé selon la revendication 1, consistant en outre à déterminer le temps de réponse sur la base de la temporisation d un établissement d une liaison entre le terminal distant () et l interface client (1). 1 d une période de temps entre l envoi du premier paquet et la réception du deuxième paquet ; utiliser ledit temps de réponse pour estimer une vitesse de connexion entre le terminal distant et l interface client ; fournir une pluralité d adresses de destination, lesdites adresses de destination se rapportant à différentes quantités de contenu au niveau d un serveur (11) couplé à l interface client, chaque adresse de destination étant optimisée pour une vitesse de connexion spécifique ; recevoir une demande d adresse de destination ; sur la base dudit temps de réponse mesuré, sélectionner une adresse de destination correspondant à la demande ; et communiquer l adresse de destination sélectionnée au terminal distant. 6. Procédé selon la revendication 1, dans lequel la sélection de l adresse de destination à partir d une pluralité d adresses est basée sur une adresse demandée par le terminal distant () et le temps de réponse déterminé. 7. Procédé selon la revendication 1, dans lequel la sélection de l adresse de destination est réalisée automatiquement. 8. Procédé selon la revendication 7, consistant en outre à déterminer le débit de données provenant du terminal distant () sur la base du temps de réponse Système selon la revendication 11, dans lequel les instructions conduisent en outre le système à connecter le terminal distant () à l adresse de destination sélectionnée. 13. Système selon la revendication 11, dans lequel le temps de réponse est affecté par l encombrement sur le réseau. 14. Système selon la revendication 11, dans lequel le temps de réponse est déterminé sur la base de la temporisation d un établissement d une liaison entre le terminal distant () et l interface client. 9. Procédé selon la revendication 7, dans lequel l adresse de destination comprend une adresse de destination principale et une pluralité de sous-adresses, chacune desdites sous-adresses correspondant à une vitesse de connexion et étant optimisée pour ladite vitesse de connexion.. Procédé selon la revendication 7, consistant en outre à déterminer un encombrement sur le réseau sur la base du temps de réponse déterminé. 11. Système comportant une interface client (1), destiné à être utilisé avec un terminal distant () et un serveur (11), comprenant des instructions résidant dans un support de stockage compréhensible par une machine, instructions qui conduisent le système à: Procédé selon la revendication 1, consistant en outre à: recevoir une demande d adresse de destination, provenant du terminal distant (), au niveau du serveur (11) ; et réécrire la demande de façon à inclure l adresse de destination sélectionnée optimisée pour la vitesse de connexion déterminée du terminal distant (). 16. Procédé selon la revendication 1, dans lequel la sélection de l adresse de destination est réalisée en réaction à une demande reçue. envoyer un premier paquet depuis l interface client (1) à un terminal distant () ; recevoir au niveau de l interface client un deuxième paquet provenant du terminal distant ; déterminer un temps de réponse du terminal distant au niveau de l interface client sur la base 7

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11 EP B1 REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is for the reader s convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard. Patent documents cited in the description US A [000] US A [000] 11