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Table of Contents Expand all

play_arrow Overview
- play_arrow Using Bundles to Create Logical Configurations for Physical Interfaces Overview
  - Types of Bundles Overview
  - Interface Naming Conventions for the CTP Series
- play_arrow CTP Bundle Overview
- play_arrow Transparent Encoding Overview
- play_arrow TDM/TDC Encoding Overview
  - TDM/TDC Encoding Overview
- play_arrow Ethernet Media Configuration Overview
  - Ethernet Media Configuration Overview
play_arrow Configuration
- play_arrow Configuring CTP Bundles (CTP Menu)
- play_arrow Configuring CTP Bundles (CTPView)
play_arrow Administration
- play_arrow Activating, Disabling, Deleting, or Recentering CTP Bundles
  - Activating, Disabling, Deleting, or Recentering CTP Bundles (CTPView)
  - Activating, Disabling, Deleting, or Recentering for CTP Bundles (CTP Menu)
- play_arrow Querying CTP Bundles
- play_arrow Monitoring Packet Creation and Reception and Packet Delay
- play_arrow Diagnostic Testing for CTP Bundles Overview
- play_arrow Configuring and Displaying Diagnostic Testing for CTP Bundles
- play_arrow Reducing the Number of SNMP Traps Generated for Late and Missing Packets
  - Reducing the Number of SNMP Traps Generated for Late and Missing Packets (CTP Menu)
play_arrow Troubleshooting
- play_arrow Knowledge Base
  - https://kb.juniper.net/

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Determining Optimal Packet Size for CTP Bundles Overview

date_range 26-May-23

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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.

Bandwidth for Transporting Serial Data

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 encapsulation overhead varies, but is typically either 6 or 8 bytes on serial links. This overhead causes smaller packets to be less efficient and result in serial data requiring more bandwidth.

Calculate the bandwidth required for a serial bit stream as follows:

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IP Bandwidth = [Packet Size (bytes) + 20 (bytes) + 2 (bytes) + Encapsulation Overhead (bytes) x [Packet Rate (pps)] x 8

Packet Creation Delay

Serial data received at the CTP interface must be buffered long enough to allow a packet to be created. The delay to create the packet increases as either the size of the packet increases or as the rate of the serial interface decreases. Generally, this delay is minimal except when the rate of the serial interface is low and the packet size is large. We recommend that you set the packet size to a smaller value for lower-speed serial interfaces. Table 1 provides examples of serial interface packet creation delay in milliseconds.

Table 1: Packet Creation Delay for Serial Interfaces
	Serial Interface Delay (msec)
	Packet Size (bytes)
Interface Rate (Kbps)	128	256	512	768	1024	1400
64	16.0	32.0	64.0	96.0	128.0	175.0
128	8.0	16.0	32.0	48.0	64.0	87/5
256	4.0	8.0	16.0	24.0	32.0	43.8
1024	1.0	2.0	4.0	6.0	8.0	10.9
1544	0.7	1.3	2.7	4.0	5.3	7.3
2048	.5	1.0	2.0	3.0	4.0	5.5

Performance of the IP Network

The number of packets created (packet rate) is inversely related to the packet size configured. For example, smaller packets result in a greater packet rate. When you configure the packet size, consider the packet-forwarding performance of the attached router and network. Table 2 provides examples of packet rates for various packet sizes and serial interface rates.

Table 2: Packet Rate for Various Packet Size and Serial Interface Rate Settings
	Packet Rate (Packets per Second)
	Packet Size (Bytes)
Interface Rate (Kbps)	128	256	512	768	1024	1400
64	62.5	31.3	15.6	10.4	7.8	5.7
128	125.0	62.5	31.3	20.8	15.6	11.4
256	20.0	125.0	62.5	41.7	31.3	22.9
1024	1000.0	500.0	250.0	166.7	125.0	91.4
1544	1507.8	753.9	277.0	251.3	188.5	137.9
2048	2000.0	1000.0	500.0	333.3	250.0	182.9

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Using CTP Bundles to Create Logical Configurations for Physical Interfaces

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Determining Optimal Packet Size for CTP Bundles Overview

Bandwidth for Transporting Serial Data

Packet Creation Delay

Performance of the IP Network

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Using CTP Bundles to Create Logical Configurations for Physical Interfaces

ON THIS PAGE

Determining Optimal Packet Size for CTP Bundles Overview

Bandwidth for Transporting Serial Data

Packet Creation Delay

Performance of the IP Network

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