Table of Contents

Chapter 1 POS Port Configuration. 1-1

1.1 POS Port Overview. 1-1

1.2 POS Port Configuration. 1-1

1.2.1 Entering POS Port View. 1-2

1.2.2 Adding/Deleting POS Ports into/from VLAN. 1-2

1.2.3 Enabling/Disabling POS Ports. 1-2

1.2.4 Configuring POS Port Description. 1-3

1.2.5 Setting the Frame Format on a POS Port 1-3

1.2.6 Enabling the Scrambling Function on a POS Port 1-3

1.2.7 Setting Alarm Thresholds for a POS Port 1-4

1.2.8 Setting the Clock Mode on a POS Port 1-4

1.2.9 Setting the State Polling Timer on a POS Port 1-5

1.2.10 Setting the CRC Check Bit Length on a POS Port 1-5

1.2.11 Setting the Loopback Mode of a POS Port 1-5

1.2.12 Setting the Overhead Byte Type of a POS Port 1-6

1.2.13 Setting the Timeout Time for PPP Negotiation. 1-7

1.2.14 Setting the MTU of a POS Port 1-7

1.2.15 Setting the Interval for Collecting Statistic Data on a POS Port 1-7

1.3 Displaying and Maintaining POS Port Configuration. 1-8

1.4 POS Port Configuration Example. 1-8

1.5 Troubleshooting POS Port Configuration. 1-9

 

Chapter 1  POS Port Configuration

When configuring a POS port, go to these sections for information you are interested in:

l           POS Port Overview

l           POS Port Configuration

l           Displaying and Maintaining POS Port Configuration

l           POS Port Configuration Example

l           Troubleshooting POS Port Configuration

1.1  POS Port Overview

Synchronous optical network (SONET), a synchronous transmission system defined by ANSI, is an international standard transmission protocol. It adopts optical transmission where transmission rates form a sequence of STM-1 (155 Mbps), STM-4c (622 Mbps), STM-16c/STM-16 (2.5 Gbps), and STM-64 (10 Gbps), each four times the immediate lower level. Because signals are synchronous, SDH can multiplex multiple signals conveniently.

Synchronous digital hierarchy (SDH), defined by CCITT (ITU-T at present), uses a SONET rate subset.

Packet over SONET/SDH (POS) is a technology used in MAN (metropolitan area network) and WAN (wide area network) for data packet transmission.

S9500 series use SDH and SONET as its physical layer protocol, maps data packets of varying lengths into SDH/SONET synchronous load, and provides a type of high-speed and reliable point-to-point data connections.

The POS ports on S9500 series work at the rates of STM-1/OC-3 (155.52 Mbps), STM-16 (2.5 Gbps) and STM-64 (10 Gbps). POS ports use the Point-to-Point Protocol (PPP) at the data link layer and the Internet Protocol (IP) at the network layer.

1.2  POS Port Configuration

The following sections describe POS port configuration tasks:

l           Entering POS Port View

l           Adding/Deleting POS Ports into/from VLAN

l           Enabling/Disabling POS Ports

l           Configuring POS Port Description

l           Setting the Frame Format on a POS Port

l           Enabling the Scrambling Function on a POS Port

l           Setting Alarm Thresholds for a POS Port

l           Setting the Clock Mode on a POS Port

l           Setting the State Polling Timer on a POS Port

l           Setting the CRC Check Bit Length on a POS Port

l           Setting the Loopback Mode of a POS Port

l           Setting the Overhead Byte Type of a POS Port

l           Setting the Timeout Time for PPP Negotiation

l           Setting the MTU of a POS Port

l           Setting the Interval for Collecting Statistic Data on a POS Port

1.2.1  Entering POS Port View

Before configuring the POS port, enter POS port view first.

Perform the following configuration in system view.

To do …	Use the command …
Enter POS port view	interface pos interface-number

 

1.2.2  Adding/Deleting POS Ports into/from VLAN

You can add a POS port into a designated VLAN, so that it can forward the packets of that VLAN.

Perform the following configuration in POS port view.

To do …	Use the command …
Add a POS port into the VLAN	pos access vlan vlan-id
Delete a POS port from the VLAN	undo pos access vlan

 

 

1.2.3  Enabling/Disabling POS Ports

After completing the configuration of a POS port, you can use undo shutdown command to enable the POS port. You also can use undo shutdown to disable it if you want to stop data forwarding on it.

Perform the following configuration in POS port view.

To do …	Use the command …
Enable POS port	shutdown
Disable POS port	undo shutdown

 

By default, POS ports are enabled.

1.2.4  Configuring POS Port Description

Perform the following configuration in POS port view.

To do …	Use the command …
Configure a POS port description	description text
Delete the POS port description	undo description

 

By default, a POS port has no description.

1.2.5  Setting the Frame Format on a POS Port

The POS port supports two frame formats: SDH and SONET.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the frame format on the POS port to SDH/SONET	frame-format { sdh | sonet }
Restore the default frame format	undo frame-format

 

By default, the frame of a POS port is SDH.

1.2.6  Enabling the Scrambling Function on a POS Port

You may configure payload scrambling on a POS port to prevent the presence of excessive consecutive 1s or 0s to facilitate line clock signal extraction at the receiving end.

Perform the following configuration in POS port view.

To do …	Use the command …
Enable the scrambling function on the POS port	scramble
Disable the scrambling function on the POS port	undo scramble

 

By default, the scrambling function is enabled on a POS port.

1.2.7  Setting Alarm Thresholds for a POS Port

You can use the threshold command to set the SD (signal degrade) threshold or SF (signal fail) threshold for a POS port.

SD and SF alarms are used to indicate the current line performance. Both may occur when the receiver detects B2 error. The bit error rate threshold of SF is higher than that of SD, meaning when a few errors occur, SD alarms are generated; while when error rate is increased to a certain degree, SF alarms are generated, indicating the line performance is degrading seriously.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the SD and SF thresholds of the POS port	threshold { sd | sf } value
Restore the defaults	undo threshold { sd | sf }

 

If you execute the threshold command with the value argument set to X, the value of the threshold specified can be obtained using this expression: 10e-X.

By default, the SD threshold is10e-6 (meaning X takes a value of 6), and the SF threshold is 10e-3 (meaning X takes a value of 3).

Note that the SD threshold must be smaller than the SF threshold.

1.2.8  Setting the Clock Mode on a POS Port

POS ports support two clock modes:

l           Master clock mode, using internal clock signals

l           Slave clock mode, using line clock signals

When two switches are connected through POS ports, you should set one POS port in master clock mode and the other in slave clock mode. Otherwise, the clocks of the two switches may be asynchronous, and packet loss may occur.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the clock mode on the POS port to master	clock master
Set the clock mode on the POS port to slave	clock slave
Restore the default	undo clock

 

By default, a POS port is in slave clock mode.

1.2.9  Setting the State Polling Timer on a POS Port

You may configure the state polling timer on a POS port to have the protocol running on it (PPP for example) regularly send ECHO Requests. If the port receives no response from the peer within the specified time limit, it regards that the peer has failed.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the state polling timer on the POS port	timer hold seconds
Restore the default	undo timer hold

 

By default, the polling interval is 10 seconds. If you set the polling interval as 0, the system does not perform link validity check.

1.2.10  Setting the CRC Check Bit Length on a POS Port

The POS port supports 16-bit and 32-bit CRC check.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the CRC check bit length on the POS port to 16 bits	crc 16
Set the CRC check bit length on the POS port to 32 bits	crc 32
Restore the default	undo crc

 

By default, the CRC check bit length is 32 bits.

 

 

1.2.11  Setting the Loopback Mode of a POS Port

Loopback is set for testing some special functions. Do not use it when the system works normally.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the loopback mode of the POS port to internal	loopback internal
Set the loopback mode of the POS port to external	loopback external
Disable loopback on the POS port	undo loopback

 

By default, loopback is disabled on a POS port.

 

 

1.2.12  Setting the Overhead Byte Type of a POS Port

SDH provides many overhead byte types for monitoring at different levels.

Signal label byte C2 belongs to the high-order path overhead byte, and is used to indicate the multiplexing structure and message payload of the VC (virtual container) frame.

Regenerator section trace byte J0 belongs to the section overhead byte, and is used to check port connectivity at section level.

Path trace byte J1 also belongs to the high-order overhead byte, and is used to check port connectivity at path level.

Perform the following configuration in POS port view.

To do …	Use the command …
Set the overhead byte type for the POS port	flag c2 flag-value flag { j0 | j1 } { sdh | sonet } flag-value
Restore the default overhead byte type	undo flag c2 undo flag { j0 | j1 } { sdh | sonet }

 

 

By default, c2 is 0x16 (hexadecimal); J0 and J1 are default.

C2, J0 and J1 configuration should be consistent at both ends. Otherwise, the system may give alarms. The frame format of overhead bytes J0 and J1 must be consistent at both POS ports. Otherwise, the system cannot read the peer field values correctly.

1.2.13  Setting the Timeout Time for PPP Negotiation

During negotiation, PPP shall retransmit a message if it receives no response from the peer within the defined time limit. You can customize the timeout time for PPP negotiation.

Perform the following configuration in POS port view.

To do …	Use the command …
Set timeout time for PPP negotiation	ppp timer negotiate seconds
Restore the default value	undo ppp timer negotiate

 

By default, the timeout time for PPP negotiation is 3 seconds.

1.2.14  Setting the MTU of a POS Port

Perform the following configuration in POS port view.

To do …	Use the command …
Set the MTU of the POS port	mtu mtu-value

 

By default, the MTU is 1,500 bytes.

Note that you must disable the port by using the shutdown command first and then use the undo shutdown command to enable it again if the MTU values are different between the two ends. In this case, as the result of the negotiation between the two ports, the smaller value will be used as the MTU.

1.2.15  Setting the Interval for Collecting Statistic Data on a POS Port

Perform the following configuration in POS port view.

Follow these steps to configure the interval for collecting statistic data on a POS port.

To do …	Use the command …	Remarks
Set the interval for collecting statistic data on the port	flow-interval interval	Required 300 seconds by default

 

The switch collects statistics data on the port to get the average rate in the interval.

1.3  Displaying and Maintaining POS Port Configuration

Operation	Command	Remarks
Display all information about POS port(s)	display interface pos [ interface-number ]	Available in any view
Clear the statistics of POS port(s)	reset counters interface pos [ interface-number ]	Available in user view
Enable/disable POS port debugging	[ undo ] debugging ppp { { ipcp | lcp } { all | error | event | packet | state } | all | core event | ip packet | mpls-multicast packet | mpls-unicast packet | osi-npdu } [ interface { aux | pos } interface-number ]	Available in user view

 

1.4  POS Port Configuration Example

I. Network requirements

Configure Switch A and Switch B to make them communicate with each other through POS ports. Switch B provides the clock.

II. Network prerequisites

None

III. Network diagram

As shown in Figure 1-1, Switch A and Switch B are interconnected by POS 2/1/1 and POS 3/1/1, whose addresses are 202.38.163.10/24 and 202.38.163.11/24.

Figure 1-1 Network diagram for directly-connected POS port configuration

IV. Configuration procedure

1)         Configure Switch A

# Create a VLAN interface with an IP address for the VLAN to which the POS port is to be assigned.

<Switch A> system-view

[Switch A] vlan 2

[Switch A-vlan2] interface vlan-interface 2

[Switch A-Vlan-interface2] ip address 202.38.163.10 255.255.255.0

[Switch A-Vlan-interface2] quit

# Add the POS port to the VLAN.

[Switch A] interface pos 2/1/1

[Switch A-Pos2/1/1] pos access vlan 2

2)         Configure Switch B

# Create a VLAN interface with an IP address for the VLAN to which the POS port is to be assigned.

<Switch B> system-view

[Switch B] vlan 2

[Switch B-vlan2] interface vlan-interface 2

[Switch B-Vlan-interface2] ip address 202.38.163.11 255.255.255.0

[Switch B-Vlan-interface2] quit

# Add the POS port to the VLAN.

[Switch B] interface pos 3/1/1

[Switch B-Pos3/1/1] pos access vlan 2

# Configure the clock source.

[Switch B-Pos3/1/1] clock master

1.5  Troubleshooting POS Port Configuration

Symptom 1:

The POS port is down at the physical layer.

Solution:

Check that

l           The receiver (Rx) and transmit (Tx) optical fibers are connected correctly to the POS ports. If the Tx and Rx ends of a optical fiber both are connected to the same POS port, then you can see the information “loopback detected” when performing the display interface pos command even if loopback function is not enabled yet.

l           The right optical module (providing the POS ports) is inserted.

Symptom 2:

The POS port has been enabled at the physical layer, but the link does not report the Up state.

Solution:

Check that

l           Inconsistent physical parameters, such as POS port clock, scrambling setting, are set at the two ends.

l           Inconsistent link data layer protocols are set at the two ends.

l           The port CRC settings are consistent at the two ends.

l           Loopback is not set on the port.

l           The VLAN to which the port belongs has been administratively shut down.

Symptom 3:

Serious IP packet loss.

Solution:

Check that:

l           The clock configuration on the POS ports is correct (otherwise, a large amount of CRC errors may result).

l           The same MTU is set at the two ends.