ADTRAN 1202060L2-1, Руководство пользователя

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Chapter 1. Introduction
1-2 TSU LT User Manual 1202060L2-1
The T1 signal originally used a type of framing known as D4
Superframe which identifies how the T1 is multiplexed.
Extended Superframe (ESF) is an enhancement of that
framing format. ESF provides a non-disruptive means of full
time monitoring on the digital facility. It was originally used
by the service provider to monitor the performance of their
service offering. Since the introduction of ESF, equipment
that is installed in private networks can also provide the
same performance information to the user.
Fractional T1
Fractional T1 (FT1) allows the buyer to purchase less than a
full T1 circuit between two points. Most carriers offer
fractional T1 in increments of 56 or 64 kbps. Connection is
made to the same network elements. The network allows
multiple users to share the same interoffice T1 bandwidth.
FT1 remains almost exclusively an inter-exchange carrier
(IXC) service. Local exchange carriers (LECs) typically do
not offer FT1, so the user’s proximity to the IXC’s point-of-
presence (POP) is key in the savings that fractional T1 offers.
FT1 local access is available in two forms:
• 56 kbps - In 56 kbps the required number of digital data
service (DDS) lines is extended from the IXC POP and
the bandwidth is combined at the office on an outbound
T1 circuit. The user pays for the individual 56K lines and
the amount of the interoffice T1 utilized
•
Full T1 line
- In T1 access, the user pays for a full T1 to
the IXC POP and then only for the bandwidth utilized.