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ATM IMA Configuration Overview

M7i, M10i, M40e, M120, and M320 routers with 4-port COC3 Circuit Emulation PICs and 12-port T1/E1 Circuit Emulation PICs support inverse multiplexing over ATM (IMA). The 12-portT1/E1 PIC supports discrete T1 ATM IMA. The 4-portCOC3 PIC supports channelized OC3/STM1 (down to T1) ATM IMA.

The 4-port COC3 Circuit Emulation PIC and 12-port T1/E1 Circuit Emulation PIC support the ATM (IMA) protocol at the T1/E1 level with up to 4 IMA groups with from 2 to 8 IMA links each.

Note: Circuit Emulation PICs require firmware version rom-ce-9.3.pbin or rom-ce-10.0.pbin for ATM IMA functionality on M7i, M10i, M40e, M120, and M320 routers running JUNOS OS Release 10.0R1 or later.

This section includes the following topics:

IMA Version

Either IMA 1.0 (af-phy-0086.000-IMA) or IMA 1.1 (af-phy-0086.001-IMA) can be selected through the CLI. If not specified, IMA 1.1 is selected by default.

IMA 1.0 and IMA 1.1 do not interoperate.

IMA Groups

You can configure up to 42 IMA groups. Each group can contain from 1 to 32 links.

Group Frame Size

When you create an IMA group, you can choose a frame size of 32, 64, 128, or 256. Frame size can be selected independently in each direction and in each group. If not specified, 128 is the default group frame size.

Transmit Clock

When you create an IMA group, you can configure common transmit clock independent transmit clock mode to reflect the PRS of the clock for each link in a group. Common mode is the default.

IMA Group Symmetry

• Symmetrical configuration and operation (default)
• Symmetrical configuration and asymmetrical operation

Asymmetrical configuration and operation are not supported.

The mode can be configured through the CLI when an IMA group is created.

Minimum Active Links

PTx is the minimum number of links required to be active in the transmit direction for the IMA group to move into the operational state. PRx is the minimum number of links required to be active in the transmit direction for the IMA group to move into the operational state. You configure PTx and PRx through the CLI when an IMA group is created. By default, 1 is selected.

For a symmetrical configuration, PTx is equal to PRx.

State Transition Variables: Alpha, Beta, and Gamma

You can configure the IMA frame synchronization link state transition variables—alpha, beta, and gamma—through the CLI. The valid range and default value are shown in Table 1.

IMA Link Addition and Deletion

When an IMA group is up, you can add links to or delete links from the group without dropping cells.

IMA Test Pattern Procedure

A test pattern procedure is supported. You can use the CLI to start and end the test pattern procedure.

Per-PIC Limit on the Number of Links

The per-PIC limit on the number of links with the 12-port T1/E1 Circuit Emulation PIC is up to 12 T1 or E1 links.

• T1p to 168
• E1p to 126
• Mixed: total bandwidth limited to 2xOC3; 258,048,000 bps

IMA Group Alarms and Group Defects

Table 2 shows the supported IMA group alarms and their associated IMA standard requirement numbers.

Table 3 shows the supported IMA group defects and their associated IMA standard requirement numbers.

IMA Link Alarms and Link Defects

Table 4 shows the supported IMA link alarms and their associated IMA standard requirement numbers.

Table 5 shows the supported IMA link defects and their associated IMA standard requirement numbers.

IMA Group Statistics

• Near-end failure count
• Far-end failure count
• Rx faulty cells due to address mismatch
• Running seconds
• Unavailable seconds

For more information about IMA group statistic, see the show interfaces command description in the Junos OS Operational Mode Commands.

IMA Link Statistics

Table 6 shows the IMA link statistics.

IMA

Clocking is applicable only to IMA links. The clocking statement does not apply to the at-x/y/g interface because the IMA group it represents is a virtual interface.