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Using Bundles to Create Logical Configurations for Physical Interfaces, CTP Release 7.3, CTPView Release 7.3
Related
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Determining Optimal Packet Size for CTP Bundles Overview
Bandwidth for Transporting Serial Data
8
a circuit continuously operates without a buffer recenter, even when clock references
are not used.
There are two types of adaptive clocking:
Adaptive clocking with internal clock—Recovers the clock from the user equipment
connected to the remote CTP device and uses it to generate both transmit and receive
timing. All clocking is performed by the DDS, which is initially configured to be locked
to the local system clock. When packets begin to flow between the CTP devices, the
adaptive clock begins time domain analysis of the packets that arrive from the remote
CTP device. Based on this analysis, adjustments are made to the DDS clock to
approximate the frequency of the clock used to create network-bound packets on the
remote CTP. In this way, the local CTP port can maintain long-term frequency lock
with the remote CTP and pass this clock to the locally connected user equipment.
Adaptive clocking with external TX clock—Data received from the local user equipment
that is bound to the IP network is clocked using the CTP external user clock (the transmit
timing clock). Data received from the remote CTP device and bound for the interface
is adaptively clocked with the recovered clock from the user equipment connected to
the remote CTP device. This configuration allows for independent adaptive configuration
in each direction. With this method, the user equipment can send packets into the
network with their local clock, and the remote end CTP devices adaptively recover this
clock. This clocking method is useful when the port speed is high or the cable length
between the user equipment and CTP device is large.
Configuring Adaptive Clocking for CTP Bundles (CTP Menu) on page 117
Configuring Adaptive Clocking for CTP Bundles (CTPView) on page 115
You can specify the size of IP packets that are created from data received at the serial
port. The CTP device uses packet size along with the serial interface rate to calculate
the packet rate; that is, the rate that packets are created. The maximum packet rate is
1500 packets per second.
To determine the optimal packet size, consider the following:
Bandwidth for transporting serial data
Packet creation delay
Performance of the IP network
For example, larger packet sizes are more bandwidth-efficient, but introduce more delay
during packet creation.
When considering bandwidth in relation to deciding packet size, add overhead for both
the Layer 2 encapsulation and the IP header. The IP header comprises 20 bytes; and the
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