SIP ALGs: bulk-call-mode and call-distribution

The following conditions can lead to a SIP bulk call or SIP "fat" session: 

• Multiple users are behind SIP proxies at either end of a Juniper firewall.
• Multiple SIP calls are ongoing between the users via these SIP proxies and through the firewall.
• All SIP traffic is using the same 5 tuples.

This feature introduces two CLI statements that allows you to load balance the SIP traffic by distributing it to all available services processing units (SPUs).