The low-speed tributary signals multiplexed to form an SDH signal are called channels. The channelized POS (CPOS) interface makes full use of SDH to provide the following benefits:

· Provides precise bandwidth division.

· Reduces the number of low-speed physical interfaces on devices.

· Enhances aggregation capacity.

· Improves the access capacity of leased lines.

CPOS interfaces

The device supports the CPOS interfaces in Table 1.

Table 1 CPOS interfaces

Interface type	Channelization/multiplexing capabilities
CPOS E1	63 E1 channels (E1 channel configurable).
CPOS T1	84 T1 channels (T1 channel configurable).
High-speed CPOS interfaces:
2.5 Gbps CPOS	OC-48/OC-48c (STM-16)

Overhead bytes

SDH provides layered precise monitoring and management.

SDH monitoring functions are implemented using overhead bytes. SDH provides monitoring at section and channel levels.

· Sections are subdivided into regenerator and multiplex sections.

· Channels are subdivided into higher-order and lower-order paths.

SDH provides a variety of overhead bytes, but only those involved in CPOS configuration are discussed in this section.

SOH

The section overhead (SOH) is further classified into the regenerator section overhead (RSOH) and the multiplex section overhead (MSOH).

The J0 regenerator section trace byte is included in RSOH to repeatedly send the section access point identifier. The receiver uses this identifier to make sure it is in continuous connection with the sender. This byte can be any character in the network of the same carrier. If the networks of two carriers are involved, the sending and receiving devices at network borders must use the same J0 byte. With the J0 byte, carriers can detect and troubleshoot faults in advance or use less time to recover networks.

POH

The payload of an STM-N frame includes the path overhead (POH), which monitors low-speed tributary signals.

The SOH monitors the section layer, and the POH monitors the path layer. The POH is divided into the higher-order path overhead and the lower-order path overhead.

Higher-order path overhead monitors paths at the VC-4/VC-3 level.

Similar to the J0 byte, the higher-order VC-N path trace byte J1 is included in the higher-order path overhead to repeatedly send the higher-order path access point identifier. The receiving end of the path uses this identifier to make sure it is in continuous connection with the specified sender. The sender and the receiver must use the same J1 byte.

In addition, the path signal label byte C2 is included in the higher-order path overhead to indicate the multiplexing structure of VC frames and the properties of payload, including the following:

· Whether the path is carrying traffic.

· What type of traffic is carried.

· How the VC frames are mapped.

The sender and receiver must use the same C2 byte.

CPOS interface application scenarios

CPOS E1/T1 interfaces are typically used to aggregate E1 and T1 lines, as shown in Figure 1.

High-speed CPOS interfaces are typically used to aggregate E3 or T3 lines, as shown in Figure 2.

In actual applications, the connection between low-end devices and the CPOS interfaces might span more than one transmission network and might require relay. This is similar to the scenario where low-end devices are connected to a high-end device through one or multiple leased lines.

Figure 1 CPOS E1/T1 interface application scenario

Figure 2 High-speed CPOS interface application scenario

CPOS interface configuration task list

Task at a glance	Remarks
Configure a CPOS E1 interface: · (Required.) Configuring the operating mode of an interface card · (Required.) Configuring basic functions of a CPOS interface · (Required.) Configuring an E1 channel	N/A
Configure a CPOS T1 interface: · (Required.) Configuring the operating mode of an interface card · (Required.) Configuring basic functions of a CPOS interface · (Required.) Configuring a T1 channel	N/A
Configure a 2.5 Gbps CPOS interface: · (Required.) Configuring basic functions of a CPOS interface · (Required.) Configuring the operating mode of a 2.5 Gbps CPOS interface	N/A

Configuring the operating mode of an interface card

The CPOS interface cards can operate in different modes to provide different types of interfaces. You must make sure a CPOS interface card is operating in the desired mode before you configure the interfaces on it. For more information about interface card mode configuration, see device management in Fundamentals Configuration Guide.

Configuring basic functions of a CPOS interface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter CPOS interface view.	controller cpos cpos-number	N/A
3. (Optional.) Configure the interface description.	description text	By default, the description of a CPOS interface is interface name Interface, for example, Cpos1/1/1 Interface.
4. Set the framing format.	frame-format { sdh \| sonet }	The default setting is SDH.
5. Set the clock mode.	clock { master \| slave }	The default setting is slave.
6. (Optional.) Set the loopback mode.	loopback { local \| remote }	By default, loopback is disabled.
7. Set the AUG multiplexing mode.	multiplex mode { au-3 \| au-4 }	The default setting is AU-4. The command is available only in SDH framing.
8. Configure the SOH and higher-order path overhead bytes.	flag { c2 path-number c2-value \| s1s0 path-number s1s0-value } flag { j0 \| j1 path-number } { sdh \| sonet } flag-value	By default: · c2 is 0x02. · s1s0 is 0x00 for SONET and 0x02 for SDH. · j0 is 0x01 for SONET and a 16-byte empty character string for SDH. · j1 is a 64-byte empty character string for SONET and a 16-byte empty character string for SDH.
9. Set the physical state change suppression interval on the interface.	link-delay seconds	By default, the physical state change suppression interval is 0 seconds.
10. 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) and the SF threshold is 10e to the power of negative 3 (10e–3).
11. (Optional.) Configure the action to take when an RDI, SD, or SF alarm occurs on the CPOS 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.
12. (Optional.) Restore the default settings for the CPOS interface.	default	N/A
13. Bring up the CPOS interface.	undo shutdown	By default, a CPOS interface is up. If no cable is connected to a physical interface, shut down the interface with the shutdown command to prevent problems.

Configuring an E1 channel

The serial interfaces created for E1 channels have the same logical features as a synchronous serial interface. You can configure these serial interfaces in the same way you configure a standard synchronous serial interface. For more information about configuring synchronous serial interfaces, see "Configuring WAN interfaces."

To configure an E1 channel:

Step	Command		Remarks
1. Enter system view.	system-view		N/A
2. Enter CPOS interface view.	controller cpos cpos-number		N/A
3. Set the framing format for the E1 channel.	e1 e1-number frame-format { crc4 \| no-crc4 }		The default setting is no-CRC4.
4. Set the clock mode for the E1 channel.	e1 e1-number clock { master \| slave }		The default setting is slave.
5. (Optional.) Enable loopback on the E1 channel.	e1 e1-number loopback { local \| payload \| remote }		By default, loopback is disabled.
6. Set overhead bytes for the E1 channel.	e1 e1-number flag c2 c2-value e1 e1-number flag j2 { sdh \| sonet } j2-string		By default, C2 is set to hexadecimal 02, and J2 contains cyclic empty character strings.
7. Configure the E1 channel operating mode.		· Specify the unframed mode: e1 e1-number unframed · Specify the framed mode and bundle timeslots: a. (Optional.) undo e1 e1-number unframed b. e1 e1-number channel-set set-number timeslot-list range	By default, an E1 channel operates in framed mode and is not channelized. When you place an E1 channel in unframed mode, the system automatically creates a 2.048 Mbps serial interface. When you bundle timeslots on an E1 channel in framed mode, the system automatically creates a serial interface for the bundle. The rate of the serial interface is identical to 64 kbps x number of bundled timeslots.
8. (Optional.) Shut down the specified E1 channel.	e1 e1-number shutdown		By default, an E1 channel is up.

Configuring a T1 channel

The serial interface created for T1 channels have the same logical features as a synchronous serial interface. You can configure these serial interfaces in the same way you configure a standard synchronous serial interface. For more information about configuring synchronous serial interfaces, see "Configuring WAN interfaces."

To configure a T1 channel:

Step	Command		Remarks
1. Enter system view.	system-view		N/A
2. Enter CPOS interface view.	controller cpos cpos-number		N/A
3. Set the framing format for the T1 channel.	t1 t1-number frame-format { esf \| sf }		The default setting is ESF.
4. Set the clock mode for the T1 channel.	t1 t1-number clock { master \| slave }		The default setting is slave.
5. (Optional.) Enable loopback on the T1 channel.	t1 t1-number loopback { local \| payload \| remote }		By default, loopback is disabled.
6. Set overhead bytes for the T1 channel.	t1 t1-number flag c2 c2-value t1 t1-number flag j2 { sdh \| sonet } j2-string		By default, C2 is set to hexadecimal 02, and J2 contains cyclic empty character strings.
7. Configure the T1 operating mode.		· Specify the unframed mode: t1 t1-number unframed · Specify the framed mode and bundle timeslots: a. (Optional.) undo t1 t1-number unframed b. t1 t1-number channel-set set-number timeslot-list range [ speed { 56k \| 64k } ]	By default, a T1 channel operates in framed mode and is not channelized. When you place a T1 channel in unframed mode, the system automatically creates a 1.544 Mbps serial interface. When you bundle timeslots on a T1 channel, the system automatically creates a serial interface for the bundle. The rate of the serial interface is identical to timeslot rate (54 kbps or 64 kbps) x number of bundled timeslots.
8. (Optional.) Shut down the specified T1 channel.		t1 t1-number shutdown	By default, a T1 channel is up.

Configuring the operating mode of a 2.5 Gbps CPOS interface

A high-speed CPOS interface supports the following operating modes:

· Channelized mode—Demultiplexes one high-order STM-N frame into four low-order STM-N frames. In this mode, you can transmit multiple channels of data over one fiber. Each channel has dedicated bandwidth and an independent control policy. This mode is suitable for transmitting multiple channels of low-speed signals.

· Concatenated mode—Processes one STM-N frame as a whole unit without demultiplexing. All STM-N signals on the fiber transmit one channel of data. The same control policy applies to all data. This mode is suitable for transmitting a channel of high-speed signal.

Set the operating mode of a 2.5 Gbps CPOS interface depending on the line rates you want.

· To provide a 2.5 Gbps line, place the CPOS interface in concatenated mode. This task is identical to channelizing the CPOS interface into a 2.5 Gbps channel.

· To provide 622 Mbps lines, place the CPOS interface in channelized mode, and then create 622 Mbps channels in concatenated mode.

· To provide 155 Mbps lines, channelize the CPOS interface into 622 Mbps channels in channelized mode, and then create 155 Mbps channels on the 622 Mbps channels.

You can configure these channel interfaces as described in "Configuring POS interfaces."

Channelizing a 2.5 Gbps CPOS interface into 622 Mbps channels

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter 2.5 Gbps CPOS interface view.	controller cpos interface-number	N/A
3. Configure the interface to operate in channelized mode.	· using oc-48 · undo using	By default, a 2.5 Gbps CPOS interface operates in channelized mode.
4. Create a 622 Mbps channel and enter its view.	oc-12 oc-12-number	By default, no 622 Mbps channels exist on a 2.5 Gbps CPOS interface. You can create up to four 622 Mbps channels on a 2.5 Gbps CPOS interface.
5. Configure the 622 Mbps channel to operate in concatenated mode.	using oc-12c	By default, a 622 Mbps channel operates in channelized mode. When you place a 622 Mbps channel in concatenated mode, a 622 Mbps POS interface is created automatically for the channel.

Channelizing a 622 Mbps channel into 155 Mbps channels on a 2.5 Gbps CPOS interface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter 2.5 Gbps CPOS interface view.	controller cpos interface-number	N/A
3. Configure the interface to operate in channelized mode.	· using oc-48 · undo using	By default, a 2.5 Gbps CPOS interface operates in channelized mode.
4. Create a 622 Mbps channel and enter its view.	oc-12 oc-12-number	By default, no 622 Mbps channels exist on a 2.5 Gbps CPOS interface.
5. Configure the 622 Mbps channel to operate in channelized mode.	· using oc-12 · undo using	By default, a 622 Mbps channel operates in channelized mode.
6. Create a 155 Mbps channel and enter its view.	oc-3 oc-3-number	By default, no 155 Mbps channels exist on a 622 Mbps channel. You can create up to four 155 Mbps channels on a 622 Mbps channel.
7. (Optional.) Configure the 155 Mbps channel to operate in concatenated mode.	using oc-3c	A 155 Mbps channel created on a 2.5 Gbps CPOS interface can only operate in concatenated mode. When you create a 155 Mbps channel, the system sets its operating mode to concatenated automatically. When you place a 155 Mbps channel in concatenated mode, a 155 Mbps POS channel interface is created automatically for the channel.

Displaying and maintaining CPOS interfaces

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

Task	Command
Display CPOS interface status information.	display controller cpos [ cpos-number ]
Display status information for an E1 channel on a CPOS interface.	display controller cpos cpos-number e1 e1-number
Display status information for a T1 channel on a CPOS interface.	display controller cpos cpos-number t1 t1-number
Display information about an E1/T1 serial interface.	display interface serial interface-number/channel-number:set-number
Clear statistics for a CPOS interface.	reset counters controller cpos interface-number

For more information about the display interface serial command, see Interface Command Reference.

CPOS interface configuration examples

CPOS-E1 interface configuration example

Network requirements

As shown in Figure 3, branch nodes Router B through Router H are uplinked to the central node Router A through E1 links. Router A aggregates these E1 links by using a CPOS interface.

Add one additional E1 link on Router B to expand its capacity, and use an MP-group interface to bind the two E1 links.

Figure 3 Network diagram

Configuration procedure

IMPORTANT:

For correct network synchronization, make sure the master clock mode is configured on the SONET/SDH devices connected to the routers.

1. Configure Router A:

# Configure E1 channels 1 and 2 of CPOS 1/1/1 to operate in unframed mode.

<RouterA> system-view

[RouterA] controller cpos 1/1/1

[RouterA-Cpos1/1/1] e1 1 unframed

[RouterA-Cpos1/1/1] e1 2 unframed

# Create MP-group 1 and assign an IP address to it.

[RouterA] interface mp-group 1/1/1

[RouterA-Mp-group1/1/1] ip address 10.1.1.1 24

[RouterA-Mp-group1/1/1] quit

# Assign Serial 1/1/1/1:0 to MP-group 1/1/1.

[RouterA] interface serial1/1/1/1:0

[RouterA-Serial1/1/1/1:0] ppp mp mp-group 1/1/1

[RouterA-Serial1/1/1/1:0] quit

# Assign Serial 1/1/1/2:0 to MP-group 1/1/1.

[RouterA] interface serial1/1/1/2:0

[RouterA-Serial1/1/1/2:0] ppp mp mp-group 1/1/1

[RouterA-Serial1/1/1/2:0] quit

2. Configure Router B:

# Configure E1 1/1/1 to operate in E1 mode.

<RouterB> system-view

[RouterB] controller e1 1/1/1

[RouterB-E1 1/1/1] using e1

[RouterB-E1 1/1/1] quit

# Configure E1 1/1/2 to operate in E1 mode.

[RouterB] controller e1 1/1/2

[RouterB-E1 1/1/2] using e1

[RouterB-E1 1/1/2] quit

# Create MP-group 1/1/1 and assign an IP address to it.

[RouterB] interface mp-group 1/1/1

[RouterB-Mp-group1/1/1] ip address 10.1.1.2 24

[RouterB-Mp-group1/1/1] quit

# Assign Serial 1/1/1:0 to MP-group 1/1/1.

[RouterB] interface serial1/1/1:0

[RouterB-Serial1/1/1:0] ppp mp mp-group 1/1/1

[RouterB-Serial1/1/1:0] quit

# Assign Serial 1/1/2:0 to MP-group 1/1/1.

[RouterB] interface serial1/1/2:0

[RouterB-Serial1/1/2:0] ppp mp mp-group 1/1/1

[RouterB-Serial1/1/2:0] quit

Verifying the configuration

# Verify the serial interface configuration and state, for example, on Router B.

<RouterB> display interface serial 1/1/1:0

# Verify the MP interface, and MP bundle configuration and state, for example, on Router B.

<RouterB> display interface mp-group 1/1/1

<RouterB> display interface display ppp mp

# Verify that the routers can ping one another. (Details not shown.)

High-speed CPOS interface configuration example

Network requirements

As shown in Figure 4, create 155 Mbps POS channel interfaces for data transmission on the 2.5 Gbps CPOS interfaces between the routers.

Figure 4 Network diagram

Configuration procedure

1. Configure Router A:

# Set the clock mode to master on the 2.5 Gbps CPOS interface.

<RouterA> system-view

[RouterA] controller cpos 1/1/1

[RouterA-Cpos1/1/1] clock master

# Create a 155 Mbps POS channel interface.

[RouterA-Cpos1/1/1] oc-12 4

[RouterA-Cpos1/1/1-oc-12-4] oc-3 4

[RouterA-Cpos1/1/1-oc-12-4-oc-3-4] using oc-3c

# Assign an IP address to the 155 Mbps POS channel interface.

[RouterA-Cpos1/1/1-oc-12-4-oc-3-4] interface pos 1/1/1/4/4:0

[RouterA-pos1/1/1/4/4:0] ip address 10.110.4.1 255.255.255.0

2. Configure Router B:

# Create a 155 Mbps POS channel interface.

<RouterB> system-view

[RouterB] controller e-cpos 1/1/1

[RouterB-Cpos1/1/1] oc-12 4

[RouterB-Cpos1/1/1-oc-12-4] oc-3 4

[RouterB-Cpos1/1/1-oc-12-4-oc-3-4] using oc-3c

# Assign an IP address to the 155 Mbps POS channel interface.

[RouterB-Cpos1/1/1-oc-12-4-oc-3-4] interface pos1/1/1/4/4:0

[RouterB-pos1/1/1/4/4:0] ip address 10.110.4.2 255.255.255.0

Verifying the configuration

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

Troubleshooting CPOS interfaces

Loop and link layer protocol down state detected on serial interfaces created for E1 channels on the CPOS interface

Symptom

The H3C router is connected to another vendor's router through E1 channels on CPOS interfaces across an SDH network. PPP is used on the serial interface created for the E1 channel set.

The output from the display interface serial command shows the following errors:

· The physical state of the serial interface is up, but the link protocol is down.

· The serial interface is in a looped condition.

Solution

The symptom might occur when the router and its directly connected SDH device have different multiplex paths for the E1 channels. Multiplex path inconsistency can cause PPP negotiation failure because the SDH device transmits signals from the router in incorrect timeslots to the remote end. If the SDH device incorrectly maps a signal to an idle timeslot in a looped condition, the router can detect a loop on the serial interface.

To resolve the problem:

1. Identify the multiplex path for the E1 channels on the router.

<H3C> display controller cpos e1

2. Verify that the router and its directly connected SDH device have the same multiplex path for E1 channels. (Details not shown.)

3. Debug the loop condition.

<H3C> debugging ppp lcp error

4. If the problem persists, contact H3C Support.

03-Interface Configuration Guide

Configuring CPOS interfaces

Overview

Overhead bytes

SOH

POH

CPOS interface application scenarios

CPOS interface configuration task list

Configuring an E1 channel

Configuring a T1 channel

Configuring the operating mode of a 2.5 Gbps CPOS interface

Channelizing a 2.5 Gbps CPOS interface into 622 Mbps channels

Channelizing a 622 Mbps channel into 155 Mbps channels on a 2.5 Gbps CPOS interface

Displaying and maintaining CPOS interfaces

CPOS interface configuration examples

Network requirements

Configuration procedure

Verifying the configuration

Network requirements

Configuration procedure

Verifying the configuration

Troubleshooting CPOS interfaces

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