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Function Description

4/1553-HSC 901 101/2 Uen B 2009-02-27

Each time a change occurs in the dynamic IP address table in the IP

DSLAM (that is, each time a user receives or releases an IP address), the

IP address table is saved to the Domain File Server. Each time the IP

DSLAM restarts, it will download the IP address table from the Domain File

Server.

For each entry (IP address), the IP DSLAM also saves the line (from which

it came), the real time, the lease time and the MAC address. When the

entry is retrieved, the IP DSLAM checks that the IP address is still valid

(with respect to the current time, the time the address was given and the

lease time). If the IP address is not valid, it will be discarded.

The remote storage is also used for storing traffic counters, that is, the

frame counter for downstream traffic and the frame counter for upstream

traffic. The counter will normally be reset when an IP DSLAM restarts.

When the counters are stored in the remote storage, the counters can

upload with the values before the restart.

To survive situations where the domain server is not available after a

reboot, the IP DSLAM keeps a copy of the saved remote storage data in

RAM. This RAM is not erased at reboot. When the IP DSLAM restarts, it

will check the validity of the RAM storage area first and use this copy

without fetching any data from the remote storage file. The remote storage

file can therefore be seen as the non-volatile backup of the remote storage

data, which is kept locally in RAM in the IP DSLAM itself.

3.2.7.1 Time Synchronization

In order to be able to time stamp entries in the Remote Storage, and

evaluate them when they are retrieved, the IP DSLAM has a real time

synchronization. A Simple Network Timing Protocol (SNTP) agent is

implemented in the IP DSLAM. The IP DSLAM synchronizes upon reboot,

and then every 12 hours.

The IP DSLAM can synchronize with any SNTP server, either in the Access

Domain, or with a central server. Figure 16 on page 29 illustrates both

scenarios. In the Access Domain1, there is a Time Synchronization Server

in the Domain, and the IP DSLAMs synchronize with it. The server is

synchronized with the Access Providers Main Time Server or any other

Time Server. Access Domain2 does not have a Time Synchronization

Server and the IP DSLAMs must therefore synchronize directly with the

main external Time Server.

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Ericsson EDN312 Guía de usuario Pagina 32