Sizing up VoIP servers
3Com, Avaya, Siemens, and Zultys offer rich telephony features, excellent voice quality, and more or less scalabilityFollow @infoworld
You are limited to using Siemens telephones with the HiPath, a limitation some may not like. But you can use either IP phones or standard digital phones. If you already have a Siemens PBX, this can make upgrading a lot less intrusive. Through the management tools, you can designate who is authorized to make changes to the phones.
One nice feature is a backup utility that supports a magneto-optical disk. If something bad happens to your PBX, at least you won't have to start again from scratch. In addition, you can network the HiPath 4000 to other Siemens units for redundancy. Likewise, the HiPath 4000 itself can carry redundant processors and power supplies for those mission-critical applications (aren't nearly all phone systems mission critical?). Networked HiPaths can be administered centrally.
In addition to hardware redundancy, Siemens also provides backup management options. Along with the Web management interface, the company includes not only a CLI, but also an X Windows client.
Finally, Siemens' own softphone is pricey, and although the company does not support the use of the X-Ten and 3Com softphones, both are much less expensive and they work just fine.
The good news about the Zultys MX250 is that it's completely standards-based. This is a pure SIP PBX. The bad news is ... well, there isn't any bad news. This PBX did exactly what the people at Zultys said it would do and did it very nicely indeed. Even better, because it is a standard SIP implementation, it worked perfectly with our Spirent Abacus test equipment and we were able to confirm that the product performs exactly as Zultys says it will. The voice quality, as we've learned to expect from today's IP phones and PBX hardware, was excellent.
The MX250 itself is a 2U box with dual IBM PowerPC processors running MontaVista Software's Hard Hat Linux. The company says that the MX250 was designed from the ground up as an IP PBX platform, rather than being a telephony platform with IP grafted on, or a computer with telephony grafted on. While it's not clear that this gives the MX250 any real operational advantages, what is clear is that this product is nicely integrated and feature rich.
While the MX250 is limited to 250 users, you can network 32 MX250s together over Ethernet to support as many as 8,000 users. Zultys includes a management application that runs on Windows, which is downloaded from the MX250. There's also a Web-based management interface.
Adding users requires only a simple form, but if you have a lot of users, you can upload a CSV file created using Excel or something similar. The company says that an LDAP interface will be available in the near future.
One of the benefits of a standards-based PBX is that it will support inexpensive, nonproprietary devices. While we used the ZIP 4X4 IP telephone from Zultys for the tests, you can use any phone that meets SIP standards. This includes SIP-based softphones and software such as Microsoft Windows Messenger (assuming Service Pack 2 doesn't change things).