This chapter describes how to configure physical parameters for POS interfaces, including standard POS interfaces, POS subinterfaces, and POS channel interfaces.

Before you configure the link and network layer parameters on a POS interface, you must perform the tasks in this chapter to configure its physical parameters.

Overview

Packet over SONET/SDH (POS) is a technology widely used on WAN and MAN. It supports data packets such as IP packets.

SONET and SDH

Synchronous Optical Network (SONET) adopts optical transmission. It is a synchronous transmission system defined by the ANSI and is an international standard transmission protocol.

ITU-T Synchronous Digital Hierarchy (SDH) uses a SONET rate subset. SDH adopts synchronous multiplexing and a flexible mapping structure. It can add or drop low-speed tributary signals to or from SDH signals without a large number of multiplexing/demultiplexing devices. This reduces signal attenuation and decreases device investments.

POS

POS maps length-variable packets directly to SONET synchronous payloads and uses the SONET physical layer transmission standard. It offers high-speed, reliable, and point-to-point data connectivity.

The POS interfaces on the device support PPP, Frame Relay, and HDLC at the data link layer and IP at the network layer. Depending on the device model, the transmission rate of POS interfaces can be STM-1, STM-4, and STM-16. The rate of a level is four times the nearest lower level.

Configuring a standard POS interface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure the packet statistics collection interval.	flow-interval interval	By default, the packet statistics collection interval is 300 seconds for an interface.
3. Enter standard POS interface view.	interface pos interface-number	N/A
4. (Optional.) Configure the interface description.	description text	By default, the description of a POS interface is interface name Interface, for example, Pos1/1/1 Interface.
5. Set the keepalive interval.	timer-hold seconds	The default setting is 10 seconds.
6. Set the maximum number of keepalive attempts.	timer-hold retry retries	The default setting is 5. The interface determines that the remote end is down if it does not receive a keepalive response after the maximum number of keepalive attempts have been made.
7. Set the clock mode.	clock { master \| slave }	The default setting is slave.
8. Set the CRC length.	crc { 16 \| 32 }	The default setting is 32 bits.
9. (Optional.) Set the loopback mode.	loopback { local \| remote }	By default, loopback is disabled.
10. Configure the overhead bytes.	· Configure the C2 path signal label byte: flag c2 flag-value · Configure the J0 regenerator section trace byte: flag j0 { sdh \| sonet } flag-value · Configure the J1 path trace byte: flag j1 { sdh \| sonet } flag-value	By default: · The C2 byte is 0x16. · The system uses the SDH framing format. · In SDH frames, both J0 and J1 bytes are empty strings.
11. (Optional.) Ignore CRC of the J1 byte.	flag j1 ignore	By default, CRC is performed for the J1 byte.
12. Set the framing format.	frame-format { sdh \| sonet }	The default setting is SDH.
13. (Optional.) Enable payload scrambling.	scramble	By default, payload scrambling is enabled.
14. Set the data link layer protocol.	link-protocol { fr \| hdlc \| ppp \| mfr }	The default setting is PPP.
15. Set the MTU.	mtu size	The default setting is 1500 bytes.
16. (Optional.) Set the signal degrade (SD) or signal fail (SF) alarm threshold for the interface.	threshold { sd sdvalue \| sf sfvalue } *	By default, the SD threshold is 10e to the power of negative 6 (10e–6). The SF threshold is 10e to the power of negative 3 (10e–3).
17. (Optional.) Configure the action to take when an RDI, SD, or SF alarm occurs on the POS interface.	alarm-detect { rdi \| sd \| sf } action link-down	By default, the device does not take any actions on the interface when an RDI, SD, or SF alarm occurs.
18. Set the rate of the interface.	speed speed-value	The default setting is 155 Mbps.
19. Set the physical state change suppression interval on the interface.	link-delay msec milliseconds	The default setting is 0 milliseconds.
20. (Optional.) Enable interface dampening on the interface.	dampening [ half-life reuse suppress max-suppress-time ]	By default, interface dampening is disabled on POS interfaces.
21. Configure the expected bandwidth of the interface.	bandwidth bandwidth-value	By default, the expected bandwidth (in kbps) is the interface baud rate divided by 1000.
22. (Optional.) Restore the default settings for the POS interface.	default	N/A
23. Shut down and bring up the interface.	shutdown undo shutdown	By default, a standard POS interface is up. For the settings to take effect, you must perform this step. If no cable is connected to the interface, shut down the interface to prevent interface exceptions.

Configuring a POS subinterface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Create a POS subinterface and enter its view.	interface pos interface-number.subnumber [ p2mp \| p2p ]	You can create POS subinterfaces only on Frame Relay-enabled standard POS interfaces.
3. Configure the subinterface description.	description text	By default, the description of a POS subinterface is interface name Interface, for example, Pos1/1/1.1 Interface.
4. Set the MTU.	mtu size	The default setting is 1500 bytes.
5. Configure the expected bandwidth of the subinterface.	bandwidth bandwidth-value	By default, the expected bandwidth (in kbps) is the interface baud rate divided by 1000.
6. Restore the default settings for the POS subinterface.	default	N/A
7. Shut down and bring up the POS subinterface.	shutdown undo shutdown	By default, a POS subinterface is up. For the settings to take effect, you must perform this step.

Configuring a POS channel interface

POS channel interfaces are created through channelization of a high-speed CPOS interface. They work in the same way as POS interfaces. For more information about creating POS channel interfaces, see "Configuring CPOS interfaces."

To configure a POS channel interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter POS channel interface view.	interface pos interface-number	N/A
3. (Optional.) Configure the interface description.	description text	By default, the description of a POS channel interface is interface name Interface, for example, Pos1/1/1:0 Interface.
4. Set the keepalive interval.	timer-hold seconds	The default setting is 10 seconds.
5. Set the maximum number of keepalive attempts.	timer-hold retry retries	The default setting is 5. The interface determines that the remote end is down if it does not receive a keepalive response after the maximum number of keepalive attempts have been made.
6. Set the CRC length.	crc { 16 \| 32 }	The default setting is 32 bits.
7. Configure the overhead bytes.	· Configure the C2 path signal label byte: flag c2 flag-value · Configure the J1 path trace byte: flag j1 { sdh \| sonet } flag-value	By default: · The C2 byte is 0x16. · The system uses the SDH framing format. · In SDH frames, the J1 byte is an empty string.
8. (Optional.) Ignore CRC of the J1 byte.	flag j1 ignore	By default, CRC is performed for the J1 byte.
9. (Optional.) Enable payload scrambling.	scramble	By default, payload scrambling is enabled.
10. Set the data link layer protocol.	link-protocol { fr \| hdlc \| ppp \| mfr }	The default setting is PPP.
11. Set the MTU.	mtu size	The default setting is 1500 bytes.
12. Set the physical state change suppression interval on the interface.	link-delay msec milliseconds	The default setting is 0 milliseconds.
13. Configure the expected bandwidth of the interface.	bandwidth bandwidth-value	By default, the expected bandwidth (in kbps) is the interface baud rate divided by 1000.
14. (Optional.) Restore the default settings for the POS channel interface.	default	N/A
15. Shut down and bring up the interface.	shutdown undo shutdown	By default, a POS channel interface is up. For the settings to take effect, you must perform this step.

Enabling subinterface rate statistics collection

IMPORTANT:

The subinterface rate statistics collection feature is resource intensive. When you enable this feature, make sure you fully understand its impact on system performance.

This feature refreshes subinterface rate statistics periodically.

To enable subinterface rate statistics collection:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter POS interface view or POS channel interface view.	interface pos interface-number	N/A
3. Enable subinterface rate statistics collection for the POS interface or the POS channel interface.	sub-interface rate-statistic	By default, subinterface rate statistics collection is disabled.
4. (Optional.) Display collected statistics.	display interface pos	N/A

Configuring B1/B2/B3 alarms for standard POS interfaces

B1, B2, and B3 bytes indicate the signal transmission performance of a line at different levels.

· B1 alarm occurs if the bite error rate of a complete STM-N frame exceeds the B1 alarm threshold.

· B2 alarm occurs if the bite error rate of an STM-1 frame exceeds the B2 alarm threshold.

· B3 alarm occurs if the bite error rate of a multiplexed signal (VC3 or VC4 frame) in the STM-1 frame exceeds the B3 alarm threshold.

To generate SNMP notifications about these alarms, you must set the alarm thresholds and enable the notifications.

For more information about SNMP notifications, see Network Management and Monitoring Configuration Guide.

To configure the B1, B2, or B3 alarm for a standard POS interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter standard POS interface view.	interface pos interface-number	N/A
3. Enable the SNMP notification about the B1, B2, or B3 alarm.	snmp-agent trap enable { b1-tca \| b2-tca \| b3-tca }	By default, SNMP notifications about B1, B2, and B3 alarms are enabled on a standard POS interface.

Changing the interface type

IMPORTANT:

This feature is available only on routers installed with HIM-TS8P interface modules.

You can change the interface type between POS and GigabitEthernet. When you change the interface type, the system performs the following operations:

· Removes the original interface.

· Creates a new-type interface with the same number as the original interface.

· Enters the interface view of the new-type interface.

Changing a standard POS interface to a Layer 3 GigabitEthernet interface

Step	Command
1. Enter system view.	system-view
2. Enter standard POS interface view.	interface pos interface-number
3. Change the interface to a Layer 3 GigabitEthernet interface.	port-type switch gigabitethernet

Changing a Layer 3 GigabitEthernet interface to a standard POS interface

Step	Command
1. Enter system view.	system-view
2. Enter Layer 3 GigabitEthernet interface view.	interface gigabitethernet interface-number
3. Change the interface to a standard POS interface.	port-type switch pos

Displaying and maintaining POS interfaces

Execute display commands in any view and reset commands in user view.

Task	Command
Display information about POS interfaces.	display interface [ pos [ interface-number \| interface-number.subnumber ] ] [ brief [ description \| down ] ]
Clear statistics for POS interfaces.	reset counters interface [ pos [ interface-number \| interface-number.subnumber ] ]

POS interface configuration examples

Directly connecting routers through POS interfaces

Network requirements

As shown in Figure 1, connect the routers through POS interfaces.

Figure 1 Network diagram

Configuration procedure

1. Configure POS 1/1/1 on Router A:

# Assign an IP address to the interface.

<RouterA> system-view

[RouterA] interface pos 1/1/1

[RouterA-Pos1/1/1] ip address 10.110.1.10 255.255.255.0

# Configure the data link layer protocol of the interface.

[RouterA-Pos1/1/1] link-protocol ppp

# Set the MTU to 1500 bytes for the interface.

[RouterA-Pos1/1/1] mtu 1500

# Shut down, and then bring up the interface for the settings to take effect.

[RouterA-Pos1/1/1] shutdown

[RouterA-Pos1/1/1] undo shutdown

2. Configure POS 1/1/1 on Router B:

# Set the clock mode to master on the interface.

<RouterB> system-view

[RouterB] interface pos 1/1/1

[RouterB-Pos1/1/1] clock master

# Assign an IP address to the interface.

[RouterB-Pos1/1/1] ip address 10.110.1.11 255.255.255.0

# Configure the data link layer protocol of the interface.

[RouterB-Pos1/1/1] link-protocol ppp

# Set the MTU to 1500 bytes for the interface.

[RouterB-Pos1/1/1] mtu 1500

# Shut down, and then bring up the interface for the settings to take effect.

[RouterB-Pos1/1/1] shutdown

[RouterB-Pos1/1/1] undo shutdown

Verifying the configuration

# Verify the POS interface settings, for example, on Router A.

<RouterA> display interface pos

# Verify that Router A and Router B can ping each other at the POS interfaces. (Details not shown.)

Connecting routers through POS interfaces across a Frame Relay network

Network requirements

As shown in Figure 2, use POS subinterfaces to connect Router A to Router B and Router C across a Frame Relay network. The routers are all DTEs on the Frame Relay network.

Figure 2 Network diagram

Configuration procedure

1. Configure Router A:

# Set the clock mode to slave on POS 1/1/1.

<RouterA> system-view

[RouterA] interface pos 1/1/1

[RouterA-Pos1/1/1] clock slave

# Enable Frame Relay on POS 1/1/1.

[RouterA-Pos1/1/1] link-protocol fr

# Configure POS 1/1/1 as DTE.

[RouterA-Pos1/1/1] fr interface-type dte

[RouterA-Pos1/1/1] quit

# Create subinterface 1 on POS 1/1/1 and assign an IP address to it.

[RouterA] interface pos 1/1/1.1

[RouterA-Pos1/1/1.1] ip address 10.10.10.1 255.255.255.0

# Assign a virtual circuit with DLCI 50 to subinterface 1.

[RouterA-Pos1/1/1.1] fr dlci 50

[RouterA-Pos1/1/1.1-fr-dlci-50] quit

# Map DLCI 50 to the peer IP address 10.10.10.2.

[RouterA-Pos1/1/1.1] fr map ip 10.10.10.2 50

# Set the MTU to 1500 for subinterface 1.

[RouterA-Pos1/1/1.1] mtu 1500

[RouterA-Pos1/1/1.1] quit

# Create subinterface 2 on POS 1/1/1 and assign an IP address to it.

[RouterA] interface pos 1/1/1.2

[RouterA-Pos1/1/1.2] ip address 20.10.10.1 255.255.255.0

# Assign a virtual circuit with DLCI 60 to subinterface 2.

[RouterA-Pos1/1/1.2] fr dlci 60

[RouterA-Pos1/1/1.2-fr-dlci-60] quit

# Map DLCI 60 to the peer IP address 20.10.10.2.

[RouterA-Pos1/1/1.2] fr map ip 20.10.10.2 60

# Set the MTU to 1500 for subinterface 2.

[RouterA-Pos1/1/1.2] mtu 1500

[RouterA-Pos1/1/1.2] quit

2. Configure Router B:

# Set the clock mode to slave on POS 1/1/1.

[RouterB] interface pos 1/1/1

[RouterB-Pos1/1/1] clock slave

# Enable Frame Relay on POS 1/1/1.

[RouterB-Pos1/1/1] link-protocol fr

# Configure POS 1/1/1 as DTE.

[RouterB-Pos1/1/1] fr interface-type dte

# Assign an IP address to POS 1/1/1.

[RouterB-Pos1/1/1] ip address 10.10.10.2 255.255.255.0

# Assign a virtual circuit with DLCI 70 to POS 1/1/1.

[RouterB-Pos1/1/1] fr dlci 70

[RouterB-Pos1/1/1-fr-dlci-70] quit

# Map DLCI 70 to the peer IP address 10.10.10.1.

[RouterB-Pos1/1/1] fr map ip 10.10.10.1 70

# Set the MTU to 1500 for POS 1/1/1.

[RouterB-Pos1/1/1] mtu 1500

3. Configure Router C in the same way Router B is configured. (Details not shown.)

Verifying the configuration

# Verify the POS interface settings.

<RouterA> display interface pos

# Verify that Router A and Router B can ping each other. (Details not shown.)

# Verify that Router A and Router C can ping each other. (Details not shown.)

Troubleshooting POS interfaces

Interface physically down

Symptom

The physical state of the POS interface is down.

Solution

To resolve the problem:

· Verify that the POS interface is connected correctly to the remote port.

¡ The transmit connector at one end must be connected to the receive connector at the other end.

¡ The transmit and receive connectors of the POS interface are not connected by the same fiber. If they are connected by the same fiber, the display interface command displays the "loopback detected" message, whether or not the loopback detection feature is enabled.

· If the two POS interfaces are directly connected, verify that the two ends use different clock mode settings.

· If the problem persists, contact H3C Support.

Data link layer down

Symptom

The physical layer is up, but the data link layer is down.

Solution

To resolve the problem:

· Verify that the two ends have matching clock mode, scrambling setting, and physical parameters.

· Verify that the two ends have the same data link layer protocol.

· If the problem persists, contact H3C Support.

Packet loss

Symptom

A large number of IP packets are dropped.

Solution

To resolve the problem:

· Verify that the correct clock mode is configured on the POS interface.

Incorrect clock mode setting can incur a large number of CRC errors.

· Verify that the two ends have the same MTU setting.

· If the problem persists, contact H3C Support.

03-Interface Configuration Guide

SONET and SDH

POS

Configuring a standard POS interface

POS interface configuration examples

Verifying the configuration

Connecting routers through POS interfaces across a Frame Relay network

Verifying the configuration

Troubleshooting POS interfaces

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