HP Survivable Branch Communication zl Module powered by Microsoft Lync Planning and Design Guide 2011-02

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Design Considerations
Planning Call Capacity
If using E1 lines, you could purchase one Two-Port T1/E1 Telephony Card and
one One-Port T1/E1 Telephony card. Alternatively, you could purchase one
Four-Port T1/E1 Telephony card and reserve the other slot for future needs.
Considerations for Remote Communications and
Planning Your WAN Link
All of the following communications must travel across the branch’s WAN link:
■ Communications between branch users and users at other sites or remote
users
■ Calls that are routed out PSTN gateways at other sites
■ Conferences
Therefore, you must plan adequate bandwidth on the WAN link.
Note These calls, as well as other calls, also pass through the LAN. However, a LAN
typically provides much more bandwidth than the calls require, so you prob-
ably do not need to plan extra bandwidth specifically to support Lync. How-
ever, if you are planning to support many video conferences, you might need
to check your LAN provisioning.
Estimate Bandwidth for Calls
To estimate the WAN bandwidth required, you first must determine the
maximum number of concurrent calls that will travel over your WAN connec-
tion. These include both PSTN calls that are typically routed out gateways at
other sites as well as peer-to-peer calls to Lync users at other sites.
As when you plan your PSTN lines (see “Considerations for Local PSTN Calls
and Planning Your Telephony Cards” on page 2-5), it is best to obtain accurate
records of the site’s current usage:
■ You might have an existing Lync (or Microsoft Office Communication
Server [OCS] 2007) solution that you are upgrading for survivability with
the SBM. In this case, use this solution’s reports and logs to calculate the
maximum number of concurrent calls to users at other sites and to PSTN
numbers. Remember to subtract from this number any PSTN calls that
will now be routed out the local PSTN gateway. The resulting value is your
estimate for the maximum number of concurrent calls on the WAN line.
■ If you are deploying a new Lync solution at the branch site, you will need
to estimate usage patterns. You can use similar guidelines to Microsoft’s
guidelines for PSTN calls to estimate the number of simultaneous calls
that your WAN link might need to accommodate.