Installation and Operation Manual
Chapter
1 Introduction
ACE-3105, ACE-3205 Ver. 5.2
Functional Description
1-15
Upon transmission, each PW is mapped to one of the three Ethernet
transmission queues.
Each transmission queue can store up to 500 buffers.
If a PW frame is directed to a transmission queue which its 500 buffers
are full, the frame is dropped and the Tx congestion counter is increased.
•
Data buffer pool –
The buffers used for data transmission (in both directions) are allocated
from a single pool.
Each buffer size is 1600 bytes.
The number of buffers in the pool is set to the maximum numbers of
buffers that can be acquired (max. VC
¯
50 + ETH queue
¯
500).
Timeout Mechanism
ACE-3105, ACE-3205 has a built-in a timer that defines PW timeouts in the range
between 100 to 5,000,000 microseconds (
μ
s). Each specific PW can be
configured to work with the timeout function enabled or disabled. If a timeout
state is reached, the PW frame is closed and forwarded.
The timer accuracy is +500 microseconds, and the timer process comprises the
following stages:
a.
When the first cell of a packet is received, the arrival time of the cell is saved,
and the cell is stored.
b.
A background timer process task is entered every 500 microseconds, and
performs the following:
Scans and traces all PWs that are set with Timer Enabled.
If the PW already has cell/cells stored, the timer task compares the
current time with the arrival time of the first cell (which was stored in the
1st stage).
If the current time minus the arrival time is larger than the timer settings,
a timeout state takes effect and the frame is forwarded for transmission.
Alternatively, if no timeout has been reached, no action is taken.
TDM over PSN Functionality
In addition to ATM traffic emulation, ACE-3105, ACE-3205 supports pseudowire
emulation of TDM traffic over packet switched networks (MPLS or IP). Any of the
TDM interfaces can be configured to 'CES-PSN' mode to support TDM over PSN.
Two primary encapsulation modes are supported according to IETF's drafts:
•
Basic CES over PSN – encapsulation of structured N
DSO services over PSN
(without CAS). The payload size is 34–512 bytes.
•
SAToP – encapsulation of unstructured E1/T1 bit stream over PSN. The
payload size is 64–512 bytes.
For detailed description of these encapsulation modes, refer to
