48 OverviewMain and Branch Office running different releasesThe Main Office Call Server and the Branch Office can have differentsoftware releases, as long as the Main Office runs at the highest release.With the introduction of CS 1000 Release 5.0 program, Nortel’s policywill be if the main office Call Server is running CS 1000 Release 5.0, theBranch Office can run on CS 1000 Release 5.0, CS 1000 Release 4.5, orCS 1000 Release 4.0.Some functionality found in CS 1000 Release 5.0 is not available in earlierreleases. For example, CS 1000 Release 4.0 does not support Active CallFailoverIt is recommended that the software release on the Branch Office alwaysmatch the software release on the main office. In addition, it is possible tohave branch offices running different software releases.Take into consideration planning your upgrade with this mixed softwarepolicy. Customers must ensure their Branch Offices are at CS 1000 Release4.5 or CS 1000 Release 4.0 prior to upgrading the main office to CS 1000Release 5.0 to ensure a supported configuration during the upgrade period.Both the Call Server and Signaling Server in the main office must run thesame release of software.If the NRS at the Branch Office is also the Alternate NRS in the network,then both it and the Primary NRS must be running the same softwarerelease.This capability is required to support customers who are currently running anetwork of CS 1000 Release 4.0 or CS 1000 Release 4.5 branch officeswith a CS 1000 Release 5.0 main office, and who want to add one BranchOffice running CS 1000 Release 5.0. By allowing this mixed-softwareoperation, customers do not have to upgrade their entire network from aCS 1000 Release 4.0 or CS 1000 Release 4.5 to CS 1000 Release 5.0 atthe same time.If the Branch Office is running CS 1000 Release 4.0 or CS 1000 Release4.5, you do not have to upgrade the Branch Office to CS 1000 Release 5.0.Indefinite operation with a mixed-software configuration of CS 1000 Release4.0 and CS 1000 Release 4.5 branch offices and a CS 1000 Release 5.0main office is supported.For information on upgrading software, refer to "Upgrading to CS 1000Release 5.0" (page 207).Nortel Communication Server 1000Branch Office Installation and CommissioningNN43001-314 01.02 StandardRelease 5.0 20 June 2007Copyright © 2007, Nortel Networks.
