S-Access SA-REP-ETHERLINK_II-1DA-PL, Руководство пользователя

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ETHERLINK II - Repeater Manual
Page 25 of 106
S-Access
Etherlink II
LTU
SA- PAM-SR2L-4E1B/4Eth-RP, V9
G. 703 (E1-1)
G. 703 (E1-1)
ATS
Customer Premises Equipment Central Office
ETH1 Ethernet
Network
S-Access
LTU
ETH1
Ethernet
Network
SA- PAM-SR4L-4E1B/4Eth-RP, V9
DSL2
DSL1
ATS
DSL4
DSL3
Etherlink II
Figure 3.6 Example of organization of a four-pair operation mode.
The <MULTIPAIR> command is used to configure this operation mode.
3.6.1.3 Reservation
Reservation is provisioned for 2- and 4-channel S-Access ETHERLINK_II devices.
The main task of reservation is to transmit the most important data even in the case of a failure
of one or several DSL connections (contingency). Reservation should also provide an efficient
use of the bandwidth for all DSL channels used by it in the normal mode.
Reservation is not aimed at continuous transmission of important data in the case of
contingencies. When one or several DSL connections fail, a sort-term loss of Ethernet packet
and E1 data can occur.
DSL channels with the successive numbers, for example, DSL1,DSL2, or DSL2,DSL3,DSL4,
are merged into a group of channels with reservation. For these channels the traffic with the
lowest numbers has higher priority than the traffic with higher numbers. For example, DSL1 has
a higher priority than DSL2, and DSL2, in turn, has a higher priority than DSL3.
In the normal mode, each channel transmits its own data as usual.
If communication is lost in one or several channels of the reservation group, other working
channels transmit data of high-priority channels. Therefore, in the case of contingency the
system always operates as if the low-priority channels failed.
Consider reservation with two DSL1 and DSL2 channels (DSL1 has a higher priority than
DSL2). If the DSL2 channel fails, the DSL1 channel continues to operate without any changes.
If the DSL1 channel fails, the DSL2 channel transmits the data of the DSL1 channel. Hence, the
DSL1 channel should transmit the high-priority data.
If the substitute channel has a lower transmission capacity than the main channel, the volume of
the data being transmitted over it will decrease. First, the volume of WAN data will decrease up
to 1 TS, then, the number of transmitted time slots of the E1 stream will decrease, E1 being at
the end of the list of E1 streams being transmitted (i.e., in the list E1-1, E1-2, the E1-2 stream
will be deleted). First, time slots with large numbers are deleted. However, there is an exception
for TS 16, which, if transmitted, will be deleted before or after TS 0.