ZyXEL Communications MSC1000G Series, Руководство пользователя

Страница: 44 / 1168

Chapter 1 Getting to Know Your MSC
Management Switch Card User’s Guide
44
• Other applications include telemedicine, surveillance systems, remote servers systems, cellular
base stations and high-quality videoconferencing.
IMA Application
Although IP network is common today, there are still some countries using TDM (Time-Division
Multiplex) as their backbone network. TDM is a technology to transmit data, voice and video signals
using different channels and clocks on the same media.
PSTN is also based on TDM technology. E1 and T1 TDM are two well-known connections. However,
those connections are not capable of long distances. In order to increase the transmission speed
and distance, IMA (Inverse Multiplexing for ATM) is a technology that can group several E1 or T1
lines and be applied to connect remote sites and the central office (CO) site together through an
ATM network (as a backbone).
The IES can support the IMA application. With an IMA line card installed, the IES is able to be a
bridge between an IP network and an ATM network.
In the following figure, the remote site’s IMA-1 converts Ethernet packets into and from ATM cells.
Through aggregating 5 E1 lines, it can provide an uplink transmission rate of around 10 Mbps. The
traffic is transmitted through the closest connected ADM (Add-Drop Multiplexing) device and then
to the TDM network.
After travelling in the TDM network, the traffic is forwarded through another connected ADM device
to the CO site’s
IMA-2 which converts the ATM cells back into Ethernet packets.
Figure 3
IMA Application
Remote Site Traffic Flow Scenario
In remote sites, traffic coming from subscribers through a DSL line card is sent to the MSC
management card and then forwarded to the specified IMA card in your configuration. One DSL line
card can only map to one IMA card. One IMA card can handle traffic sent from multiple DSL line
cards.
ADM
ADM
IMA-2
IMA-1
Remote
Site
CO Site
TDM
one E1 line
xDSL
CPE