Abstract:
A method, a cluster system, and a computer-readable medium for distributing data packets addressed to at least one virtual address over a communication network using a protocol, which allows for at least some content of the data packet to be encrypted, to a multiplicity of service nodes. The method includes receiving incoming data packets addressed to a virtual address through a packet analyzer and identifying whether the incoming data packets are encrypted. Each encryption data packet is forwarded to a decryption module and a decrypted data packet is returned. Based on the decrypted data packet, a scheduling decision is made by a scheduling module. Scheduling data is then combined with the originally received encrypted data packet such that the encrypted data packet can be forwarded to one service node for further processing.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/698,463, filed Jul. 12, 2005, entitled “Method, Cluster System and Computer-Readable Medium for Distributing Data Packets,” the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a method, a cluster system, and a computer-readable medium for distributing data packets addressed to at least one virtual address received over a communication network using a protocol, which allows for at least some content of the data packets to be encrypted, to a multiplicity of service nodes.  
       BACKGROUND  
       [0003]     Methods and apparatuses for distributing data packets to a multiplicity of service nodes are commonly used in so-called cluster systems providing services to a large number of clients. A particular well-known example is so-called server farms providing web services to the Internet.  
         [0004]     Originally the transmission control protocol and the Internet protocol (TCP/IP) did not provide any method for packet authentication or encryption. The most popular application level protocol, the hypertext transport protocol (HTTP) also does not provide any security mechanisms.  
         [0005]     With the growing importance of web services such as e-commerce and e-business, a great need for secure Internet communication has arisen. To overcome the lack of security, various protocols for including security mechanisms like authentication and encryption were designed for the different layers of the TCP/IP protocol stack.  
         [0006]     The secure socket layer (SSL) protocol is an extra layer, added between the transport layer, managing connections between two computers, and the application layer and provides transparent authentication and encryption to higher level protocols. In practice, however, it is only commonly used in combination with the HTTP protocol, which is then referred to as secure HTTP or HTTP over SSL (HTTPS).  
         [0007]     Because of the relatively high overhead in terms of processing performance it is only used for a few types of applications such as online banking and electronic payment systems. In order to spread the use of secure communication on the Internet to other applications and application protocols, the IP security (IPsec) standard integrates authentication and encryption directly into the network layer. To this end, an additional packet header is introduced which is placed immediately after the IP header comprising the source and destination address of the packet. The additional header is placed before the TCP or UDP header of the transport layer, which comprises, among other data, the source and destination port number of the packet. The additional IPsec header can comprise either an authentication header (AH) or an encapsulated secure payload (ESP) header or both. In the case where encryption is used, the data following the ESP header is encrypted, including the data contained in a subsequent UDP or TCP header.  
         [0008]     Encryption can be used in two different modes called tunnel mode and transport mode, respectively. In tunnel mode, the entire data packet to be transmitted over a network is encrypted and included in a new data packet as payload. In transport mode, only the content of the original data packet is encrypted, but some of its header information, particularly the IP header comprising source and destination address and the ESP header comprising encryption information remain unencrypted.  
         [0009]     If such a partially encrypted data packet is received by a single server, the decryption of the packet&#39;s content takes place before the packet is passed to the transport layer and processing can proceed in the same way as without encryption.  
         [0010]     If the IP packet is received by a cluster system, however, data packets are usually distributed to different service nodes of the cluster for further processing. In order to decide which packet is to be processed by what service node, a packet analyzer usually scans the headers of the received packets for service information, such as the port number or application protocol. This information, however, is not available at the network layer in case of an encrypted IPsec packet. Consequently, IPsec is currently not used in cluster systems identified by a common virtual address, but always directed to a physical address of a single server. This has the disadvantage that the scalability and reliability of cluster systems currently cannot be used in combination with the security offered by the IPsec standard.  
       SUMMARY  
       [0011]     According to the invention, at least partially encrypted data packets are distributed to a plurality of service nodes with minimal changes to existing cluster systems, particularly without modification to existing packet schedulers. Data packets addressed to at least one virtual address received over a communication network using a protocol, which allows for at least some content of the data packets to be encrypted, are distributed to a multiplicity of service nodes. A cluster system is provided that includes a multiplicity of service nodes, at least one gateway node, a packet analyzer that analyzes destination addresses and encryption states of incoming data packets, a packet decryption module comprising a predefined key that decrypts encrypted content of data packets, and a packet scheduler that determines which of the service nodes to be used for data packets addressed to at least one virtual address based on data packets&#39; content. An incoming data packet addressed to a virtual address through the gateway is received and the encryption state of the received data packet is identified via the packet analyzer. If no encryption is identified, the received data packet is scheduled via the packet scheduler. If encryption is identified, the encryption data packet is decrypted via the packet encryption module and the decrypted data packet is scheduled via the packet scheduler. The received data packet is then distributed to one of the service nodes according to the scheduling.  
         [0012]     The inventive method has the advantage that an existing packet scheduler can be used to make scheduling decisions even if received data packets are partially encrypted. According to the present invention partially encrypted data packets are picked up by a packet analyzer and decrypted before a decrypted version of the packet is sent on to the packet scheduler. After the packet scheduler has made a scheduling decision based on the decrypted content of the data packet, the data packet can be replaced by the encrypted version again, such that the service node or any higher level protocol tools are not aware of the intermediate decryption. Thus, the inventive method can be introduced transparently to an existing cluster system.  
         [0013]     In a first embodiment of the present invention, incoming encrypted data packets are temporarily stored by the packet analyzer and a decrypted copy of the packet is sent to the packet scheduler for scheduling. The decision of the packet scheduler is returned to the packet analyzer, which then sends the originally received packet onto the service node according to the decision of the packet scheduler.  
         [0014]     In another implementation of the method, an additional packet exchange module is provided, which picks up previously encrypted packets, which were decrypted for the packet scheduler and replaces them with the originally encrypted data packets, which are forwarded from the packet analyzer to the packet exchange module. This embodiment has the advantage that it can be implemented in a typical queue oriented software system.  
         [0015]     The above and still further features and advantages of the present invention will become apparent upon consideration of the following definitions, descriptions and descriptive figures of specific embodiments thereof wherein like reference numerals in the various figures are utilized to designate like components. While these descriptions go into specific details of the invention, it should be understood that variations may and do exist and would be apparent to those skilled in the art based on the descriptions herein. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention will be described in the following using exemplary embodiments shown in the following figures.  
         [0017]      FIG. 1  shows a first exemplary embodiment of the present invention.  
         [0018]      FIG. 2  shows a second exemplary embodiment of the present invention.  
         [0019]      FIG. 3  shows a flow chart of an exemplary embodiment of the inventive method. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 1  shows a cluster system  1  comprising a gateway node  2  and three service nodes  3 A,  3 B, and  3 C. Each of the service nodes  3 A,  3 B and  3 C has a unique address  18 A,  18 B, and  18 C respectively. The gateway node  2  and the service nodes  3  are connected through an internal network  11 . The gateway node  2  comprises a packet analyzer  4 , a packet decryption module  5  and a packet scheduler  6 . The packet decryption module  5  contains a decryption key  17 , and the packet analyzer  4  comprises at least one predetermined virtual address  12 . In addition, the gateway node  2  is connected to a communication network  10 .  
         [0021]     The packet analyzer  4  receives data packets from the communication network  10 . Packet analyzer  4  checks whether incoming packets are address to the predetermined virtual address  12  and whether the incoming packets are encrypted. If an encrypted packet  7  is found, a copy of the encrypted packet  7  is stored and the packet  7  is forwarded to the packet decryption module  5 .  
         [0022]     The packet decryption module  5  decrypts the encrypted data packet  7  using the decryption key  17  and returns a decrypted packet  8  to the packet analyzer  4 .  
         [0023]     The decrypted packet  8  is then forwarded to the packet scheduler  6 , which makes a scheduling decision based on the decrypted packet&#39;s content. Scheduling data  9  is then returned from the packet scheduler  6  to the packet analyzer  4 , either alone or contained in the decrypted packet  8 . For example, the packet scheduler  6  can return its scheduling decision by overwriting the virtual address  12  originally contained in the data packet  8  with one of the unique addresses  18 A,  18 B or  18 C of the service nodes  3 A,  3 B or  3 C. Alternatively the packet scheduler  6  can add an additional header to the returned data packet  8 .  
         [0024]     The packet analyzer  4  combines the stored encrypted packet  7  with the received scheduling data  9  and forwards the resulting data packet to the internal network  11 . For example, a destination address  18 A,  18 B or  18 C contained in a modified or additional header of the returned data packet  8  can be included in the stored encrypted packet  7 . The data packet  7  is then forwarded to one of the service nodes  3 A,  3 B,  3 C for further processing.  
         [0025]     If an open, i.e., unencrypted data packet, is received by the packet analyzer  4  from the data network  10 , the packet is forwarded directly to the packet scheduler  6 , without prior decryption or intermediate storage.  
         [0026]     The embodiment shown in  FIG. 1  has the additional advantage that all processing of the unencrypted data packet  8  takes place within the gateway node  2 . Thus, even in cases were the internal communication network  11  is deemed to be insecure, e.g., because it is an open network connecting service nodes  3  at locations different from the location of the gateway node  2 , the data exchanged over the networks  10  and  11  remains secure.  
         [0027]      FIG. 2  shows another exemplary embodiment of the present invention. A cluster system  13  comprises a gateway node  2 , a routing node  14 , a decryption node  15  and three service nodes  3 A,  3 B, and  3 C with addresses  18 A,  18 B, and  18 C, respectively. All nodes are connected by an internal network  11 . The gateway node  2  is further connected to a communication network  10 .  
         [0028]     The gateway node  2  comprises a packet analyzer  4 . The packet analyzer  4  analyzes incoming data packets and compares them with at least one predetermined virtual address  12 . If an encrypted packet  7  is detected by the packet analyzer  4 , the encrypted data packet  7  is forwarded to a decryption module  5  of the decryption node  15  and to a packet exchange module  16  of the routing node  14 .  
         [0029]     The decryption module  5  decrypts the incoming encrypted packet  7  using a decryption key  17  and returns a decrypted packet  8  to the gateway node  2 . The gateway node  2  then forwards the decrypted data packet  8  to a packet scheduler  6  of the routing node  14 . Alternatively, the decryption node  15  can also forward the decrypted packet  8  to the routing node  14  directly.  
         [0030]     The packet scheduler  6  inside the routing node  14  makes a scheduling decision based on the decrypted data packet  8  and adds scheduling data  9 , typically the address  18 A,  18 B, or  18 C of one of the service nodes  3 A,  3 B, or  3 C to the data packet  8 . Because the packet scheduler  6  receives only decrypted packets  8 , i.e., data packets without any IPsec information, all scheduling algorithms and systems developed for the original IP protocol can be utilized without change.  
         [0031]     The modified data packet  8  is then detected and picked up by the packet exchange module  16 , which also runs within the routing node  14 . For example, the packet exchange module  16  could analyze source address of data packets  7  scheduled by the packet scheduler and compare them with source addresses of the forwarded encrypted data packet  7 . The authentication header used by IPsec also contains a packet sequence number, which can be used for identification of data packets to be exchanged. The packet exchange module  16  then exchanges the decrypted data packet  8  with the encrypted data packet  7 , which was previously sent to it. At the same time, exchange module  16  maintains the scheduling data  9 , e.g., its new destination address  18 A,  18 B, or  18 C. The encrypted data packet  7  comprising the scheduling data  9  is then forwarded to one of the service nodes  3 A,  3 B, or  3 C for further processing.  
         [0032]     As in the previous embodiment, the inventive method can also be used in a network, in which unencrypted data packets are received by the gateway node  2 . If an unencrypted data packet  8  is received by the packet analyzer  4 , it is simply forwarded to the scheduling module  6  and ignored by the packet exchange module  16 . Thus, the performance of existing systems for distributing data packets in a cluster system can be maintained for unencrypted data traffic, while allowing supporting encrypted data traffic.  
         [0033]     As shown by the two different embodiments shown in  FIGS. 1 and 2 , the different functional modules  3 ,  4 ,  5 ,  6  and  16  of the cluster system  1  and  13  can be either implemented in hardware or software. Forwarding data packets from one module to another can be achieved either by means of software interfaces or by physically sending them from one node of the cluster system  1  or  13  to another. In practice, many of the nodes of the cluster system  1  and  13  will be replicated for reasons of performance and reliability. In case several redundant gateway nodes  2  and/or decryption nodes  5  exist, all packet decryption modules  5  must contain the same decryption key  17 .  
         [0034]     As previously mentioned, the IPsec standard also allows for authentication of data packets. If authentication is desired, either alone or in addition to the encryption of data packets, such functionality can be implemented using the same architecture as described above and shown in  FIG. 1  and  2 , respectively.  
         [0035]     In this case an additional authentication module, either as part of the gateway node  2  or as a separate node of the cluster system  1  or  13  respectively must be provided. If the packet analyzer  4  identifies an incoming data packet containing an authorization header, the packet is forwarded to the authentication module prior to making a scheduling decision. If the packet is deemed to be authentic, it is forwarded to the scheduling module  6 . Otherwise, the packet may be rejected or forwarded to a special node or module for further analysis, e.g., to analyze whether a safety-critical attack on the cluster system  1  or  13  is being carried out over the data network  10 .  
         [0036]     If both AH and ESP headers are present, they are analyzed and processed in the order they are included in the received data packet  7 , i.e., a data packet containing a AH header followed by an ESP header is authenticated first and decrypted afterwards and vice versa.  
         [0037]     A flow chart summarizing the above-described methodology, including both authentication and decryption of data packets, is shown in  FIG. 3 .  
         [0038]     Typically, outgoing data packets returned from the service nodes  3  to a client node over the network  10  also will be encrypted. In order to make good scheduling decisions, the packet scheduler  6  needs to maintain information about open connections between any client system and service node  3 , such that all requests belonging to one connection are send to the same service node  3 . Thus, it is important to scan outgoing data packets for connection closure. However, outgoing data packets may be encrypted, such that data required to determine the state of an connection is not available to the packet scheduler  6 .  
         [0039]     For this reason, in a further embodiment of the invention, data packets are scanned for connection closure before they are encrypted. This can be done, for example, by a separate encryption module used to add the IPsec headers to outgoing data packets. The gathered information can then be forwarded to the packet scheduler  6 , either through a separate interface or as part of the outgoing data packets, e.g., in form of an additional packet header. Such additional information must be stripped from the outgoing data packets before they are finally returned over the communication network  10 , for example by the packet analyzer  4 .  
         [0040]     Alternatively, outgoing data packets can be sent through the same processing queue as incoming packets, i.e., they can be analyzed, decrypted if necessary, forwarded to the scheduler and subsequently replaced with the originally encrypted outgoing data packet as described above.  
         [0041]     Having described preferred embodiments of the invention, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.  
       LIST OF REFERENCES  
       [0000]    
       
           1  Cluster system  
           2  Gateway node  
           3  Service node  
           4  Packet analyzer  
           5  Packet decryption module  
           6  Packet scheduler  
           7  Encrypted data packet  
           8  Decrypted data packet  
           9  Scheduling data  
           10  Communication network  
           11  Internal network  
           12  Virtual address  
           13  Cluster system  
           14  Routing node  
           15  Decryption node  
           16  Packet exchange module  
           17  Decryption key  
           18  Unique address