Cluster-based Web Systems

Two-Way, layer-7 request distribution mechanism

We have designed and devoloped a TCP Gateway mechanisms at the operating system kernel level, ClubWeb-2w. It has been implemented as an extension of the khttpd Web server accelerator, which works at the kernel level of the Linux operating system. The Web switch acts as an intermediary Proxy for the clients, receiving inbound connection requests and requesting the documents to the Web server nodes, according to a well defined content-aware policy. The Web switch also receives all response packets, which are forwarded to the clients. The implementation does not suffer from overheads due to context switches among server processes, since the functionality is entirely implemented at the kernel level. The design of the switch is thread-oriented, that is, a configurable number of processing units handles the distinct stages which lead to the fruition of the requested content.

One-Way, layer-7 request distribution mechanism

We have also developed a One-Way request distribution mechanisms, ClubWeb-1w, following the TCP Handoff approach. The client connects to a Web switch using plain TCP/IP and browser. The Web switch accepts the connection request and parses the content of the subsequent HTTP request. A Web server is chosen according to a well-defined scheduling policy, which is usually content-aware. Next, the TCP connection established between client and switch is transferred to the chosen server in a manner which is totally transparent to clients. As soon as connection transfer is performed successfully, the Web server elaborates a response and sends it directly to the client. From now on, client packets pertaining to the transferred connection (usually ACKs for server response segments) are forwarded by the Web switch to the appropriate Web server.
TCP Handoff requires substantial modifications to the operating system TCP/IP stack of switch and servers, but it allows for a much better scalability with respect to Two-Way content-aware routing, since server responses do not traverse the Web switch anymore.
We have designed and devoloped a small, efficient synchronization protocol in the TCP/IP network stack of the Linux operating system. It offers the functionalities for properly transferring a TCP connection from one node to another.

To see a list of people involved in the HiPerWeb project, click here.

To see a list of publications related to content-aware request distribution mechanisms, click here.

Overview | Publications | People | Algorithms |
Last updated: December 1, 2002