cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 73

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
3.2.2 Resource Allocation
3.2.3 Resource Isolation
3.2.4 Peer-to-Peer Transfers
28237-DSH-001-C
APPLICATION EXAMPLE
A system designer implements a CN8237 terminal as an ATM uplink for a
Service Access Multiplexer (SAM). The SAM is comprised of the ATM card and
several Frame Relay adapter cards. The host assigns each Frame Relay adapter
card to a set of CN8237 control and status queues at initialization. During opera-
tion, one of the Frame Relay adapter cards experiences a hardware failure. The
failure prevents the card’s processor from servicing the CN8237’s reassembly status
queue. Eventually, the CN8237 fills the queue and is unable to proceed—this situa-
tion is referred to as queue overflow. The CN8237 shuts down reassembly on VCCs
that are assigned to the overflowed queue only. Since the other cards in the
system are assigned to other status queues, their VCCs remain unaffected by the
failure.
With either physical PCI peers, logical peers, or some combination of the two
types, the CN8237 multiplexes each peer’s transmitted packets onto the line and
routes incoming packets to the appropriate peer. The host system allocates shared
resources, such as host and SAR-shared memory, VPI/VCI address space, and
CBR time slots to peers and clients arbitrarily.
Because each peer is assigned to an independent control and status path, the
CN8237 isolates the resources of each peer. Not only does this simplify resource
management, but queue error conditions caused by a single peer do not affect any
other peers.
The multiple queue architecture of the CN8237 also enables peer-to-peer PCI
transfers. The CN8237 transfers ATM cells as a PCI master. Since the buffer
control structures are independent for each peer, each identifies a unique address
range in PCI memory space. The host defines the address range of each peer. The
CN8237 transfers data within this address range. An address range corresponds
either to a region of centralized host memory or to a set of peer resident buffers.
Mindspeed Technologies
™
3.2 Multiple Client Architecture
3.0 Host Interface
3-3