Network Requirements and Preparation
Planning and Installation Guide
9 – 13
Various technologies are available from different service providers to provide IP
connectivity between locations, as shown in Table 9-9.
Leased T1
Leased T1 facilities are the most robust WAN technology available. Leased T1s are
point-to-point links that inherently meet the network requirements for toll-quality
voice since no ISP is involved. Dedicated T1s are priced on a per unit distance basis,
making this a very cost-effective option over short distances.
Frame Relay
Frame Relay is a viable option as long as you get a committed information rate (CIR)
that meets the bandwidth and network requirements for toll-quality voice
communications.
SDSL
SDSL is considered “business-to-business” DSL in which you can negotiate a service
level agreement with the service provider. Unlike T1, SDSL is priced on a flat
bandwidth basis, making the price “distance insensitive” and cost-effective over long
distances.
Although this is an excellent option, especially moving forward, ShoreTel has found the
use of SDSL challenging, since the service providers often commit to a Service Level
Agreement (SLA) they cannot fulfill. Many service providers have grown very fast, and
the IP network is a patchwork of devices. These service providers are usually geared
toward providing bandwidth for typical data applications, and a voice application
highlights weaknesses in their network. Only with joint troubleshooting of the service
provider’s network, using simple tools like ping plotters, has ShoreTel been able to
achieve the SLA the service provider promised.
Table 9-9 IP Connectivity Chart
Te c h n o l o gy Upstream Bandwidth Kbps Downstream Bandwidth Kbps Calls with ADPCM
a
a. Your bandwidth w ill vary, based on the WAN overhead for your particular system.
T1
1544
1544
26
Frame Relay Varies
Varies
Varies
SDSL
1544
1544
26
SDSL
1024
1024
17
SDSL
768
768
13
SDSL
512
512
8
SDSL
384
384
6
IDSL
144
144
1 call only
ADSL
128
1,000 (varies)
1 call only
Cable
128 (varies)
1,000 (varies)
1 call only
ISDN BRI 128
128
Not supported
Dial-up
modem
28.8–56
28.8–56
Not supported
