Chapter
1 Introduction
Installation and Operation Manual
1-14 Functional
Description
ACE-3105, ACE-3205 Ver. 5.2
ATM over PSN Functionality
This section describes the unit's ATM over PSN capabilities in terms of:
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Queues and Buffers
The traffic sent by the Gigabit Ethernet interface is mapped to four strict priority
transmit queues, as follows:
Queue 1 (highest) – Reserved for clock distribution traffic; can store up
to 50 frames.
Queue 2 – Reserved for management traffic and highest priority data;
can store up to 500 frames.
Queue 3 – Used for the second priority data; can store up to 500 frames.
Queue 4 – Used for the lowest priority data; can store up to 500 frames.
Figure
1-11. Ethernet Queue Priority
PSN Buffer Allocations
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In the PSN to ATM direction –
Frames are received on the Ethernet port and are mapped to a VPC/VCC
based on the incoming PW label.
Each frame is stored in a buffer of 1600 bytes.
Each VPC/VCC transmit channel can store up to 50 buffers.
The Tx priority of each Tx channel is determined by the connection service
category.
If a frame is received for a specific VCC/VPC that already occupies 50
buffers, the frame is dropped and the Rx congestion counter is increased.
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In the ATM to PSN direction –
Cells are received on the VCC/VPC and are mapped to a PW based on the
incoming VPI/VCI.
Each incoming cell is either concatenated to an existing PW packet or
starts a new PW packet.
Each PW packet is stored in a 1600 byte buffer.
