With the addition of a load balancer and multiple instances of the same parts2.altservice.com site on different servers, I needed to have session data stored at a central location to be accessed by each web server. Currently I use memcached, which Magento supports through the Zend Framework. So adding support is done by making sure that the php.ini has the following information:

[Session]
session.save_handler = memcached
session.save_path = "tcp://yourMemcachedIP:11211"

This sets PHP to use memcached for session storage.

Next the app/etc/local.xml in the Magento directory must be edited to define memcached storage:

<config>
<global>
    <install>
        <date></date>
    </install>
    <crypt>
        <key></key>
    </crypt>
    <disable_local_modules>false</disable_local_modules>
    <resources>
        <db>
            <table_prefix></table_prefix>
        </db>
        <default_setup>
            <connection>
            </connection>
        </default_setup>
    </resources>
    <session_save><![CDATA[memcache]]></session_save> <!-- db / memcache / empty=files -->
    <session_save_path><![CDATA[tcp://X.X.X.X:11211?persistent=1&weight=2&timeout=10&retry_interval=10]]></session_save_path><!-- e.g. for memcache session save handler tcp://10.0.0.1:11211?persistent=1&weight=2&timeout=10&retry_interval=10 -->
    <session_cache_limiter><![CDATA[private]]></session_cache_limiter><!-- see http://php.net/manual/en/function.session-cache-limiter.php#82174 for possible values -->
    <cache>
        <backend>memcached</backend><!-- apc / memcached / xcache / empty=file -->
        <slow_backend>database</slow_backend> <!-- database / file (default) - used for 2 levels cache setup, necessary for all shared memory storages -->
        <slow_backend_store_data></slow_backend_store_data> <!-- 1 / 0 (default) - used for 2 levels cache setup, sets whether store data in db slow cache backend -->
        <auto_refresh_fast_cache>1</auto_refresh_fast_cache> <!-- 1 / 0 (default) - used for 2 levels cache setup, sets whether refresh data in fast cache backend -->
        <memcached><!-- memcached cache backend related config -->
            <servers><!-- any number of server nodes can be included -->
                <server>
                    <host><![CDATA[X.X.X.X]]></host>
                    <port><![CDATA[11211]]></port>
                    <persistent><![CDATA[1]]></persistent>
                </server>
                <server>
                    <host><![CDATA[X.X.X.X]]></host>
                    <port><![CDATA[11211]]></port>
                    <persistent><![CDATA[1]]></persistent>
                </server>
            </servers>
        </memcached>
    </cache>
</global>
<admin>
    <routers>
        <adminhtml>
            <args>
                <frontName><![CDATA[admin]]></frontName>
            </args>
        </adminhtml>
    </routers>
</admin>

And finally make sure to have the internal Cache Management turned off