ATM encapsulation

Overview

SONET/SDH clear channels can be provisioned so that ATM cells are encapsulated in SONET/SDH frames. The entire SONET/SDH path of the port is then used to carry ATM cells. The channel of the port becomes the ATM interface. ATM encapsulation is supported on the following daughter cards:

• 16 × ATM OC3 SFP

• 16 × ATM OC3 SFP B

• 4 × ATM OC12/OC3 SFP

• 4 × ATM OC12/OC3 SFP B

• 4 × OC3/STM1 ASAP SFP

• 4 × Any Service Channelized OC3

• 16 × Any Service Channelized DS1/E1

SONET/SDH clear channel applications with ATM encapsulation use the following syntax:

Daughter Card Slot - 3 (16 × ATMOC3), OK
Port 3/1/1 - Speed: OC3, State: OK
Channel 3/1/1.sts3, Mode: Access, Encap: ATM, State: Ok

Customer devices with ATM interfaces are connected directly or using the ATM access network to a 7750 SR that offers IES or VPRN services.

A SONET/SDH clear channel with ATM encapsulation can carry multiple ATM PVCs. ATM PVCs cannot be created from the NFM-P. They are created automatically by the router when a new Layer 3 interface over ATM is created. The following figure shows an example of ATM PVCs on a SONET/SDH clear channel.

Figure 16-4: ATM PVCs on a SONET/SDH clear channel

ILMI links between ATM interfaces

ILMI links can be configured between ATM interfaces. ILMI is a protocol that sets and sends physical layer, ATM layer, virtual path, and virtual channel parameters that are exchanged by ATM interfaces.

When ILMI is run between two ATM interfaces, the interfaces exchange ILMI packets that consist of SNMP messages across the physical connection. An ILMI link allows ILMI to run on an available virtual channel. When an ILMI link is created to carry ILMI messages, a PVC is automatically created with default PVC attributes. The PVC is deleted when the ILMI link is removed.

IMA

IMA is supported on channelized ASAP MDAs on the 7750 SR, 7705 SAR. For Wavence device IMA support, see the NSP NFM-P Microwave Radio User Guide.

IMA group bundles aggregate E1 or DS1 ATM paths into a single logical ATM interface. Each IMA group bundle can have from 1 to 8 members, or links. Up to 56 IMA group bundles can be configured on a single 7750 SR MDA. Up to 8 IMA group bundles can be configured on a single 7705 SAR daughter card.

Each ATM Interface supports up to 48 VP/VC connection points. Each 16 × E1 ASAP Access (ETSI) board supports up to 128 VP/VC connection points.

An IMA group bundle has the following common interface properties:

• ATM encapsulation type is displayed on the ATM Interface properties form by clicking on the “Edit ATM button”.

• MTU value (of the primary link)

Member links inherit the common properties of the IMA group to which they belong. Only the properties of the primary link can be changed. The primary link is the member with the lowest interface index or initialization sequence. The primary link may change as member links are added and deleted from the IMA group.

Consider the following when you create a multilink IMA group bundle.

• When a path becomes a member of an IMA group bundle, it is no longer a physical ATM path interface.

• The members of the IMA group bundle inherit all of the properties of the primary link, such as the SONET configuration and MTU. If you modify the configuration of the primary link, the configuration of the bundle members is also modified.

• Member links that are added after the primary link has been added to the IMA group bundle must match the configuration of the primary link.

• You cannot configure services on a member link.