Voice3: Update: Recent Voice Over X Information

icon Voice3: Update: Recent Voice Over X Information


The 2600 modular router can now be used to upgrade 2500 models for "power branch offices". One of the exciting capabilities of the 2600 is using modules from the 3600 models, including the voice modules. This allows you to provide multiservice networking to branches, including voice, data, and fax integration over IP. Maximum voice port density is 4 FXS, FXO, or E&M ports.


There is now a voice/fax feature card for the AS5300. It is a coprocessor card with RISC engine and DSP's for each voice channel. Each voice feature card has 24 digital voice connections for a T1 (30 for E1). Up to two voice/fax feature cards can go into an AS5300, so the AS5300 scales to 48 (60) voice connections per chassis at present. Note that DSP's are currently rapidly increasing in capability and dropping in cost. Cisco Voice Manager software can be used to help configure and monitor the AS5300 voice capabilities, also the 2600 and 3600 voice capabilities.

One intended use of the AS5300 voice/fax feature cards is intranet calling and faxing. As with all VoX (Voice Over X) products, delay is a concern. Modern high-speed switched campus environments are the perfect setting for implementation. Leased line trunks are another well-controlled setting where good results should be possible. Sending your corporate voice over the Internet is probably not the way to impress senior management -- at least, not favorably!

Real-time fax to fax is another possible application. The voice/fax card provides T.30 spoofing, and appears to the sending and receiving fax machines as just another fax machine. Incoming fax  is demodulated before relay so the 64K PCM modulated fax call only consumes 9600 bps on your WAN.

The AS5300 is also capable of use as a gateway for LAN-based phones. Cisco suggests that this might be used with call centers to reduce the costs of long-distance trunking.

Having voice capability for the AS5300 also scales via the AccessPath integrated access system, which helps in stacking them for large-scale applications. The AccessPath TS3 accomodates 21 AS5300's, which currently gives you up to 2016 modems (in North America), or 21 x 48 = 1008 voice ports. You'd probably use the modems with 3 of the T3 trunk interfaces that are available.

Finally, Cisco has announced SS7 capability, so that large-scale dial (and soon, voice) capabilities do not require a dedicated phone switch, reducing carrier or Service Provider costs.

Other Exciting Developments

Cisco just announced the purchase of Selsius (www.selsius.com). Selsius makes
  • Selsius-Phone: full-featured phones that plug directly into the LAN
  • Selsius-CallManager: performas PBX call control on the data network
  • Selsius-Access: allows the IP PBX to connect to the Public Switched Telephone Network
Selsius claims the PBX provides simple mixed voice/data networks, with audio compression to conserve bandwidth when transmitting voice. The PBX provides traditional PBX features such as multiple lines on one phone, transfer, forward, hold, etc.

The Call Manager software works with existing telephony systems and also can supply full PBX functionality on its own. It runs on an NT server using TCP/IP and provides the PBX features listed above, plus call park, calling party id to the Selsius-Phone. There is also a Unified Messaging Interface providing connectivity to voice mail and interactive voice response systems. It works with any H.323 based client. Because CallManager is based on IP, it can be deployed as a single IP PBX with geographically dispersed users.

The Selsius-Phone is a PBX-like phone that plugs directly into an Ethernet jack. It does not require a paired PC. The phones use DHCP to make phone setup "virtually automatic". Because of this, the phones can be easily moved and plugged in anywhere on the IP network with no configuration. Models include 12 or 30 programmable buttons, speakerphone, and display, and use G.711 and G.723 audio compression. The phones are Microsoft NetMeeting enabled, so application sharing and videoconferencing are available by pressing a button on the phone. Ringing and ring volume adjustments are available, configured via Web browser.

There is also a Selsius-VirtualPhone, a software-only version.


Dr. Peter J. Welcher (CCIE #1773, CCSI #94014) is a Senior Consultant with Chesapeake NetCraftsmen. NetCraftsmen is a high-end consulting firm and Cisco Premier Partner dedicated to quality consulting and knowledge transfer. NetCraftsmen has eleven CCIE's (4 of whom are double-CCIE's, R&S and Security). NetCraftsmen has expertise including large network high-availability routing/switching and design, VoIP, QoS, MPLS, network management, security, IP multicast, and other areas. See http://www.netcraftsmen.net for more information about NetCraftsmen. . New articles will be posted under the Articles link. Questions, suggestions for articles, etc. can be sent to This email address is being protected from spambots. You need JavaScript enabled to view it. .

Copyright (C)  1996,  Peter J. Welcher