Contents

Configuring ATM interfaces· 1

About ATM interfaces· 1

ATM and DSL· 1

ATM interface types· 1

ATM interface applications· 1

ATM interface features· 1

Configuring an ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface· 2

Configuring basic settings of an interface· 2

Enabling payload scrambling on an interface· 3

Configuring overhead byte on an interface· 3

Configuring the MTU for an interface· 4

Enabling loopback on an interface· 4

Restoring the default settings for an interface· 5

Configuring an ATM subinterface· 5

About ATM subinterfaces· 5

Configuring basic settings of an ATM subinterface interface· 5

Configuring the MTU for an ATM subinterface· 6

Restoring the default settings for an ATM subinterface· 6

Display and maintenance commands for ATM interfaces· 6

Troubleshooting ATM interfaces· 7

Interface state error 7

Frequent packet dropping, CRC check errors, and interface state errors· 7

Configuring ATM interfaces

This chapter covers the physical configurations of ATM interfaces. For information about configuring ATM services, see Layer 2—WAN Configuration Guide.

About ATM interfaces

ATM and DSL

Asynchronous Transfer Mode (ATM) is a technology based on packet transmission mode and incorporates the high-speed of circuit transmission mode. It is a backbone network technology for transmission of audio, video, and data. Because of its flexibility and support for multimedia services, ATM is regarded as a core technology for implementing broadband communications.

Digital Subscriber Line (DSL) is a technology providing high-speed data transmission over copper wires. It includes the following technologies:

·     Asymmetric Digital Subscriber Line (ADSL).

·     High-bit-rate Digital Subscriber Line (HDSL).

·     Very High-rate Digital Subscriber Line (VDSL).

·     Single-pair high-speed DSL defined in ITU-T Standard G.991.2 (G.SHDSL).

·     Symmetric Digital Subscriber Line (SDSL).

These DSL technologies are different in signal transmission speed and distance and link rate symmetric mode (determined by the uplink and downlink rates).

The ATM physical layer is at the bottom of the ATM reference model. It primarily delivers valid cells and the associated timing signals between the upper layer and transmission medium. The speeds of physical access media are defined in international standards such as ATM OC-3c/STM-1 and ATM E3/T3. Most DSL applications are ATM-based, combining the advantages of ATM with the low transmission cost feature of DSL. DSL technologies have been widely adopted for broadband access.

ATM interface types

The device supports the following ATM interface types:

·     ATM OC-3c/STM-1 based on SONET/SDH—Operates in 155 Mbps.

·     ATM OC-12c/STM-4 based on SONET/SDH—Operates in 622 Mbps.

 

ATM interface applications

An ATM interface supports IPoA.

ATM interface features

ATM interfaces support the following features:

·     Constant Bit Rate (CBR).

·     Unspecified Bit Rate (UBR).

·     Variable Bit Rate-Real Time (VBR-RT).

·     Variable Bit Rate-Non Real Time (VBR-NRT).

·     Permanent Virtual Circuit (PVC).

·     Traffic Shaping based on Virtual Circuit (VC).

·     User-to-Network Interface (UNI).

·     RFC1483, Multiprotocol Encapsulation over ATM Adaptation Layer 5.

·     RFC 2225, Classical IP and ARP over ATM.

·     RFC 2390, Inverse Address Resolution Protocol.

·     F5 End to End Loopback OAM.

·     ATM Adaptation Layer 5 (AAL5).

Configuring an ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface

Configuring basic settings of an interface

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     (Optional.) Configure the interface description.

description text

By default, the description is interface-name Interface.

4.     Configure the clock mode for the interface.

clock { master | slave }

By default, the clock mode is slave.

When the ATM interfaces on two devices are connected directly through a fiber-optic cable, set the clock mode to master at one end and to slave at the other end.

The clock of the SONET/SDH network is more precise than the internal clock of ATM interfaces. When an ATM interface is connected to a SONET/SDH device, set the clock mode of the ATM interface to slave.

5.     Configure the frame format for the interface.

frame-format { sdh | sonet }

By default, the frame format is SDH.

6.     (Optional.) Configure the expected bandwidth for the interface.

bandwidth bandwidth-value

By default, the expected bandwidth (in kbps) is calculated by using the following formula: Interface baud rate/1000.

The expected bandwidth is an informational parameter used only by higher-layer protocols for calculation. You cannot adjust the actual bandwidth of an interface by using this command.

7.     Bring up the interface.

undo shutdown

By default, the interface is up.

Enabling payload scrambling on an interface

About this task

Payload scrambling enables an interface to scramble outgoing data and descramble incoming data. By preventing the presence of long strings of all 1s or all 0s, payload scrambling enables the receiving end to extract the line clock signal correctly.

Restrictions and guidelines

The payload scrambling setting must be the same at both ends of a link to ensure correct communication.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     Enable payload scrambling.

scramble

By default, payload scrambling is enabled.

Configuring overhead byte on an interface

About this task

J0 byte is a section overhead byte. SDH and SONET use this byte to test continuity of the connection between two interfaces at the section level.

J1 byte is a higher-order path overhead byte. SDH and SONET use this byte to test continuity of the connection between two interfaces at the path level.

The C2 byte is a higher-order path overhead byte. It indicates the multiplex structure of virtual container (VC) frames and the property of payload.

Restrictions and guidelines

When the C2 byte of one end is set to 1, the C2 byte of the other end can be set to any character in hexadecimal notation. If the C2 byte of either ends of a link is not set to 1, the C2 byte must be the same at both ends.

The J1 settings on the sending and receiving ends must be the same.

The J0 byte can be any character in the network of the same carrier. On networks of two carriers, the sending and receiving devices at network borders must use the same J0 byte.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     Configure the C2 path signal label byte.

flag c2 flag-value

By default, the C2 byte is 13 in hexadecimal notation.

4.     Configure the J0 regenerator section trace byte.

flag j0 { sdh | sonet } flag-value

By default, the system uses the SDH framing format, and the J0 byte value is null in SDH frames.

5.     Configure the J1 path trace byte.

flag j1 { sdh | sonet } flag-value

By default, the system uses the SDH framing format, and the J1 byte value is null in SDH frames.

Configuring the MTU for an interface

Restrictions and guidelines

The MTU setting affects the assembly and fragmentation of IP packets.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     Set the MTU.

mtu size

The default setting is 1500 bytes.

Enabling loopback on an interface

About this task

Perform this task to determine whether a link works correctly.

Loopback includes the following types:

·     Internal cell loopback—Checks physical chips on the local end.

·     Internal loopback—Checks service chips on the local end.

·     External line loopback—Checks the remote end.

Restrictions and guidelines

Loopback is intended for testing only. Disable loopback when the interface is operating correctly.

After you enable this feature on an interface, the interface does not forward data traffic.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     Enable loopback.

loopback { cell | local | remote }

By default, loopback is disabled.

Restoring the default settings for an interface

Restrictions and guidelines

This feature might interrupt ongoing network services. Make sure you are fully aware of the impact of this feature when you use it on a live network.

This feature might fail to restore the default settings for some commands because of command dependencies or system restrictions. You can use the display this command in interface view to check for these commands and perform their undo forms or follow the command reference to restore their default settings. If your restoration attempt still fails, follow the error message to resolve the problem.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM OC-3c/STM-1 or ATM OC-12c/STM-4 interface view.

interface atm interface-number

3.     Restore the default settings for the interface.

default

Configuring an ATM subinterface

About ATM subinterfaces

An ATM subinterface supports the same network layer functions as an ATM interface. The network layers of different ATM subinterfaces are independent of each other. You can configure different Layer 3 services for ATM subinterfaces, such as IP services and MPLS services. To enable an ATM interface to support multiple Layer 3 services, create multiple subinterfaces for the interface.

The rate of an ATM subinterface depends on the rates of the PVCs or PVC-groups configured on the subinterfaces.

Configuring basic settings of an ATM subinterface interface

1.     Enter system view.

system-view

2.     Create an ATM subinterface and enter its view.

interface atm interface-number.subnumber [ p2mp | p2p ]

3.     (Optional.) Configure the subinterface description.

description text

By default, the description is interface-name Interface.

4.     (Optional.) Configure the expected bandwidth for the subinterface.

bandwidth bandwidth-value

By default, the expected bandwidth (in kbps) is calculated by using the following formula: Interface baud rate/1000.

The expected bandwidth is an informational parameter used only by higher-layer protocols for calculation. You cannot adjust the actual bandwidth of an interface by using this command.

5.     Bring up the subinterface.

undo shutdown

By default, the subinterface is up.

Configuring the MTU for an ATM subinterface

Restrictions and guidelines

The MTU setting affects the assembly and fragmentation of IP packets.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM subinterface view.

interface atm interface-number.subnumber

3.     Set the MTU.

mtu size

The default setting is 1500 bytes.

Restoring the default settings for an ATM subinterface

Restrictions and guidelines

This feature might interrupt ongoing network services. Make sure you are fully aware of the impact of this feature when you use it on a live network.

This feature might fail to restore the default settings for some commands because of command dependencies or system restrictions. You can use the display this command in interface view to check for these commands and perform their undo forms or follow the command reference to restore their default settings. If your restoration attempt still fails, follow the error message to resolve the problem.

Procedure

1.     Enter system view.

system-view

2.     Enter ATM subinterface view.

interface atm interface-number.subnumber

3.     Restore the default settings for the interface.

default

Display and maintenance commands for ATM interfaces

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

 

Task	Command
Display interface traffic statistics.	display counters { inbound | outbound } interface [ atm [ interface-number ] ]
Display traffic rate statistics for interfaces in up state for the most recent statistics interval.	display counters rate { inbound | outbound } interface [ atm [ interface-number ] ]
Display ATM interface information.	display interface [ atm [ interface-number ] ] [ brief [ description | down ] ]
Clear the statistics for an interface.	reset counters interface [ atm [ interface-number ] ]

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Troubleshooting ATM interfaces

Interface state error

Symptom

The ATM interface state is down.

Solution

To resolve the problem:

1.     Verify that the Rx and Tx ends of the optical fiber are correctly connected.

2.     If the two devices are connected back-to-back, verify that the clock mode is set to master on one interface, and to slave on the other interface. The default clock mode is slave. To set the clock mode to master, use the clock master command.

3.     If the problem persists, contact H3C Support.

Frequent packet dropping, CRC check errors, and interface state errors

Symptom

Two devices connecting back-to-back can ping each other successfully. Frequent packet dropping and CRC errors occur, and the interface state flaps between up and down.

Solution

To resolve the problem:

1.     Verify that the ATM interfaces of the two sides are of the same type, for example, multimode fiber interfaces or single-mode fiber interfaces.

If a multimode fiber interface and a single-mode fiber interface are directly connected, they can communicate in most cases. However, frequent packet dropping, CRC errors, and interface state errors might occur.

2.     If the problem persists, contact H3C Support.