 |
Carrier
Managed VoIP for VPN
Enterprise VoIP services can be divided into transport
services, which carry VoIP; and signaling services, which
provide higher-layer IP telephony capabilities. VoIP transport
services can run over carrier-run IP networks, the Internet,
or traditional data services such as frame relay. Carrier-run
VoIP networks provide predictable, high-quality voice
by running across a carrier-managed IP, IP/Multiprotocol
Label Switching (MPLS), or frame relay backbone. Examples
of carrier-run IP networks used for VoIP include AT&T's
IP VPN and IP-Enabled Frame Relay, Global Crossing's On-net
Transport service, and MCI's Private IP.
These VoIP transport services can be delivered as either
managed or unmanaged services. As managed transport services,
vendors can tweak the underlying network to enhance VoIP
capabilities. AT&T's Voice over VPN service, for example,
is a managed version of its Network-Based IP VPN service,
formerly known as Enhanced VPN (EVPN). The difference
is that Voice over VPN lets routers use the Compressed
Real-Time Transfer Protocol (CRTP), which drops the 40
bytes used for IP, UDP, and RTP header fields down to
four bytes. The service also provides packet fragmentation,
which prevents large packets from congesting 64Kbps or
128Kbps access lines. AT&T also offers VoIP with its
old frame relay service, called the Managed Router Service.
MCI's Private IP doesn't offer CRTP, but does provide
packet fragmentation.
Lower-priced offerings are available through corporate
Internet-based VoIP services. By locating sites on a single
provider's Internet backbone, service providers can deliver
better predictability than would be possible across the
Internet and at a lower price point than can be had on
a privately run network. However, because these are public
backbones, SLAs aren't as good as those available on the
private IP network. An example of such a service is AT&T's
Managed Internet Service with VoIP.
Service providers can also deliver VoIP signaling services.
With CPE-based signaling services, service providers locate
a telephony server at the customer premises (or a gateway
in the case of existing telephony installations). AT&T's
IP LAN Telephony Services fall into this category. MCI
doesn't offer such a service.
Network-based (or hosted) VoIP signaling services are
built around telephony servers and gateways in the carrier's
network. MCI Advantage was the first of these services
from a major carrier and today runs over MCI's Private
IP and Dedicated Internet services. AT&T plans to
deliver such a service, but hasn't announced an availability
date. Global Crossing offers VoIP Outbound, which provides
a network of PSTN gateways that enterprises can use to
terminate their VoIP calls.
THE VPN SERVICES
By adopting VoIP VPNs, enterprises can set up company-wide
VoIP-based communications without the need for point-to-point
connections between facilities. As a result, enterprises
can achieve increased flexibility and decrease their operating
expenses substantially. Unlike traditional separate meshed
voice and data networks, each site requires only a single
converged access link to a service provider's VPN-enabled
network.
Key Features:
- Increase service provider revenue potential and
grow Enterprise base by complementing existing Centrex/Centrex
IP, PBX/IP PBX carrier-managed or IP VPN serice offerings
with value added VoIP VPN
- Cost effectively extend service provider's small
and medium Enterprise base by expanding their service
reach out-of-territory
- Reduce enterprise operational costs with a discounted
payback in less than one year
- Cost-effectively converge enterprise access into
the service provider for all their voice and data
needs
- Simplify routing and dial plan management and reduce
leased line costs for multi-site enterprises
|
|
|
|
