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Manual Chapter: Establishing Additional TCP Connections with MultiConnect
Manual Chapter
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Overview: Establishing additional TCP connections with MultiConnect

Most web browsers create a limited number of persistent TCP connections when requesting data, which restricts the amount of content a client can receive at one time. You can provide faster data downloads to your clients using the WebAccelerator™ system’s MultiConnect feature.

When enabled, the MultiConnect feature modifies embedded URLs with unique subdomains, prompting the browser to open more persistent TCP connections (up to two per subdomain generated by the WebAccelerator system). The origin web servers never get a request from these additional subdomains; they are used exclusively on embedded URLs or links that request images or scripts and are only for requests and/or responses between the client and the WebAccelerator system. If the WebAccelerator system needs to send a request to the origin server, it removes the subdomain prefixes before sending the request.

The WebAccelerator system uses the MultiConnect feature only on the following types of links:
  • Image tags: <img src="...">
  • Script tags: <script src="...">
  • Forms whose input type is an image: <form><input type="image” src="..."></form>

About optimization of TCP connections

The WebAccelerator™ system’s MultiConnect feature decreases the number of server-side TCP connections required while increasing the number of simultaneous client-side TCP connections available to a browser for downloading a web page.

Decreasing the number of server-side TCP connections can improve application performance and reduce the number of servers required to host an application. Creating and closing a TCP connection requires significant overhead, so as the number of open server connections increases, maintaining those connections while simultaneously opening new connections can severely degrade server performance and user response time.

Despite the ability for multiple transactions to occur within a single TCP connection, a connection is typically between one client and one server. A connection normally closes either when a server reaches a defined transaction limit or when a client has transferred all of the files that are needed from that server. The WebAccelerator system, however, operates as a proxy and can pool TCP server-side connections by combining many separate transactions, potentially from multiple users, through fewer TCP connections. The WebAccelerator system opens new server-side connections only when necessary, thus reusing existing connections for requests from other users whenever possible.

MultiConnect example

For this example, your site serves a simple page (http://www.siterequest.com/index.htm) that consists of several image files. The page that your site serves appears as follows:

<html> <head><title>example page</title></head> <body> <p>The images that your site serves:</p> <p><img src=”myImages/image1.jpeg”></p> <p><img src=”myImages/image2.jpeg”></p> <p><img src=”myImages/image3.jpeg”></p> <p><img src=”myImages/image4.jpeg”></p> </body> </html>

An additional subdomain prefix of wa is configured for the host map and the MultiConnect feature enabled, so the WebAccelerator™ system modifies the page and serves it as follows:

<html> <head><title>example page</title></head> <body> <p>The images that your site serves:</p> <p><img src=”http://wa1.www.siterequest.com/myImages/image1.jpeg”></p> <p><img src=”http://wa2.www.siterequest.com/myImages/image2.jpeg”></p> <p><img src=”http://wa2.www.siterequest.com/myImages/image3.jpeg”></p> <p><img src=”http://wa1.www.siterequest.com/myImages/image4.jpeg”></p> </body> </html>

Task summary for establishing additional TCP connections with MultiConnect

Perform these tasks to establish additional TCP connections with MultiConnect.

Enabling MultiConnect for HTTP traffic

Perform the following:
  • Configure DNS with entries for the additional subdomains.
  • Map the additional DNS entries to the same IP address as the base origin web server (for example, www.siterequest.com).
  • Assign specific prefixes to the additional subdomains. For example, if the requested host for the mapping is www.siterequest.com and you request two additional subdomains for the HTTP protocol, you assign a subdomain prefix of wa.
The MultiConnect feature opens additional persistent TCP connections and is optimum for sites that have a high number of first-time visitors who are downloading a large number of images or scripts.
Note: Use the MultiConnect feature only if you have low-latency, high-bandwidth links, because the additional TCP connections also increase the amount of traffic to your site.
  1. On the Main tab, click WebAccelerator > Policies. The Policies screen displays a list of existing acceleration policies.
  2. Click the name of a user-defined acceleration policy.
  3. Click a node in the Policy Tree.
  4. From the Matching Rules menu, choose Acceleration Rules.
  5. Click Assembly.
  6. Select the Enable MultiConnect check box.
  7. Click Save.
The MultiConnect feature is applied to the node and modifies embedded URLs with unique subdomains, prompting the browser to open more persistent TCP connections (up to two per subdomain generated by the WebAccelerator™ system).

Configuring subdomains

Perform the following:
  • Configure DNS with entries for the additional subdomains.
  • Map the additional DNS entries to the same IP address as the base origin web server (for example, www.siterequest.com).
  • Assign specific prefixes to the additional subdomains. For example, if the requested host for the mapping is www.siterequest.com and you request two additional subdomains for the HTTP protocol, you assign a subdomain prefix of wa.
The WebAccelerator™ system changes the domain on qualifying embedded URLs and links so that they use the domains that you specify.
  1. On the Main tab, click WebAccelerator > Applications. The Applications List screen opens.
  2. Click the name of an application.
  3. Click Options for a requested host.
  4. In the HTTP Subdomains list, select the number of HTTP subdomains that you want the WebAccelerator system to generate for each protocol. The default is 0.
  5. In the HTTPS Subdomains list, select the number of HTTPS subdomains that you want the WebAccelerator system to generate for each protocol. The default is 0.
  6. In the Subdomain Prefix field, type a prefix. The default prefix is wa.
  7. Click Save.
The WebAccelerator system changes the domain on qualifying embedded URLs and links so that they use the domains you specified. For example:
  • wa1.www.siterequest.com
  • wa2.www.siterequest.com

Implementation results

The WebAccelerator™ system is configured to modify embedded URLs with unique subdomains, prompting the browser to open more persistent TCP connections.

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