Cisco Systems ACIP-SM(=) manual ACIP Description, ACIP Features

ACIP Description

An ATM connection transfers raw bits of information to a destination router/host. The ATM router takes the common part convergence sublayer (CPCS) frame, carves it up into 53-byte cells, and sends these cells to the destination router or host for reassembly. Forty-eight bytes of each cell are used for the CPCS data; the remaining 5 bytes are used for cell routing. The 5-byte cell header contains the destination VPI/VCI, payload type, cell loss priority (CLP), and header error control.

Unlike a LAN, which is connectionless, ATM requires certain features to provide a LAN environment to the users. One such feature is broadcast capability. Protocols wanting to broadcast packets to all stations in a subnet must be allowed to do so with a single call to Layer 2. In order to support broadcasting, the router allows the user to specify a particular VC as a broadcast VC. When the protocol passes a packet with a broadcast address to the ATM driver, the packet is duplicated and sent to each VC marked as a broadcast VC. This method is known as pseudobroadcasting.

ACIP Description

The ATM Cable Interface Processor (ACIP) (see Figure 1) provides a single ATM network interface for a Cisco 7500 series router by providing a direct connection between the router’s high-speed Cisco Extended Bus (CyBus) and external equipment. The ACIP can be connected directly to a TeraLink 1000 cable headend, or through a Cisco Lightstream 1010 ATM switch or other external ATM network equipment. The physical layer interface module (PLIM) on the ACIP provides a SONET/SDH (STS-3C) interface connection.

Figure 1 ACIP with the UNI 155-Mbps Interface

U111, microcode ROM

	RX	Cells
ENABLED		Carrier
	RX

UNI 155

TX RX

H2337

ACIP Features

The ACIP supports the following features:

•Multiple rate queues.

•Reassembly of up to 512 buffers simultaneously. Each buffer represents a packet.

•Up to 2,048 virtual circuits.

•Transfer rates per VPI limited to fixed values provided by the cable headend.

•Exception queue, which is used for event reporting. Events such as CRC errors are reported to the exception queue.

•Raw queue, which is used for all raw traffic over the ATM network. Raw traffic includes Operation Administration and Maintenance (OAM) cells and Interim Local Management Interface (ILMI) cells. (ATM signaling cells are not considered raw.)

4ATM Cable Interface Processor (ACIP) Installation and Configuration