VoIP implementation advise

Hi

We wish to implement VoIP to (primarily) communicate with overseas
offices, but at the same time reduce the phone bill for the office in
general. Our two offices (one in UK, the other in Africa) are connected
via a PIX-PIX VPN. More offices in Africa should be VoIP'ed up as the
year progresses.

We have a 1 MB leased line connecting to a Cisco 2501 router (ISP
managed), then a Cisco PIX 506e, through to four 3COM 4288g manageable
network switches. Number of users on London side is about 30.

The remote side will be implementing Cisco Express.

A couple of questions -

i) Is it recommended we implement Cisco Express too, for compatibility
issues, or can we use any system (e.g. Avaya).
ii) We will outsource the implementation to external companies, but
wish to manage the maintenance. Given that none of the of the IT
department has
experience in either Cisco Express or Avaya etc, what is the most
straighforward application to learn.
iii) One method of implementation is to insert a VoIP card into our
existing Samsung phone switch and use QoS on our existing
infrastructure. Another would be to leave for the existing
infrastructure for data only and use a SIP gateway and seperate ADSL
line for voice (which one company is advising). Any thoughts? Their
claim is that QoS can only go so far, and a seperate ADSL
line/dedicated hardware is what is needed.

Would be grateful for pointers.

Cheers

dilan.weerasinghe@gmail.com

[Toubatel]

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