Reference Only / Allayer Confidential
AL101
Advance Information
8 Port 10/100 Mbit/s Dual Speed Fast Ethernet Switch
Product Description
The AL101 is an eight-port 10/100 Mbit/s dual speed Ethernet switch. A low-cost and scalable
solution for up to 32 ports is achieved through the use of low-cost buffer memory and Allayer's
proprietary RoX architecture. In addition, the AL101 supports VLAN and multiple link aggregation
trunks.
Figure 1
System Block Diagram
Supports eight 10/100 Mbit/s Ethernet ports
with RMII interface
Capable of trunking for up to 800 Mbit/s link
Full- and half-duplex mode operation
Speed auto-negotiation through MDIO
Built-in storage of 1K MAC addresses
Designed to utilize low cost SGRAM
Scalable design for stackable switch
implementation
RoX expansion link supports 4.8 Gbit/s
throughput
Serial EEPROM interface for low-cost
system configuration
Gigabit Ethernet ready
Automatic source address learning
Secure mode traffic filtering
Broadcast storm control
Port monitoring support
IEEE 802.3x flow control for full-duplex
operation
Optional backpressure flow control support
for half-duplex operation
Supports store-and-forward mode switching
VLAN support
RMON and SNMP support with external
management (MIB) device
0.35 micron, 3.3V CMOS technology
Packaged in 256-pin PQFP
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
10/100 MAC
High Speed
Switch Fabric
Switch
Controller
Address
Control
Address
Table
Buffer
Manager
Address
Table
Expansion
EEPROM
Interface
Management
Information
Expansion
Interface
AL101 Advance Information
2/2000
Reference Only / Allayer Confidential
2
AL101 Overview
The RoX interface is a 2.4 Gbit/s interface (4.8 Gbit/s full-duplex). The interface can support up to
four switch chips. Various combinations can be used for different configurations. The maximum
port configuration will be either 32-port 100 Mbit/s ports or 24-port 100 Mbit/s plus two Gigabit
Ethernet ports.
The RoX interface also supports an external management device, the AL300A. SNMP and RMON
are supported through this external management device.
The AL101 provides eight 10/100 Mbit/s Ethernet ports. Each port supports both 10 and 100
Mbit/s data rate. The operation mode is auto-negotiated by the PHY. All ports are full-duplex
capable. The device also supports VLAN for workgroup and segment switching application.
The AL101 also supports trunking applications. The chip provides two optional load balancing
schemes, explicit and dynamic. With trunking, it is possible to group up to four full-duplex links
together to form a single 800 Mbit/s link.
Data received from the MAC interface is stored in the external memory buffer. The AL101 utilizes
cost effective SGRAM to provide 8-Mbit or 16-Mbit of buffer memory.
During transmission, the data is obtained from the buffer memory and routed to the destination
port. In the event of a collision during a half-duplex operation, the MAC control will back off and
retransmit in accordance to the IEEE 802.3 specification.
The AL101 provides two flow control methods. For half-duplex operations, an optional jamming
based flow control (known as backpressure) is available to prevent loss of data. With this method of
flow control, the switch will generate a jam signal when the receive-buffer is full. The sending
station will not transmit until the line is clear. In the full-duplex mode, the AL101 utilizes IEEE
802.3x as the flow control mechanism.
All ports support multiple MAC addresses. The switch chip supports up to 1K MAC addresses
internally. These MAC addresses are shared among all eight ports. The initialization and
configuration of the switch is programmed by an external EEPROM. For an unmanaged switch
design, there is no need for a CPU. Field reconfiguration can be achieved by using a parallel
interface to reprogram the EEPROM.
For managed switch applications, the AL101 supports network management through the network
management option. When the management option is enabled, network statistics for each port are
gathered and sent across the RoX bus. The management information base chip on the bus will
collect and store the data for the network management agent. Access to the statistical counters is
provided via the CPU interface of the MIB device.
The AL101 also supports port-based VLAN. The VLAN register set is used to configure the
destination ports for multicast and broadcast frames.
The device also provides two levels of security for intrusion protection. Security can be
implemented on a per port basis.
The AL101 operates only in the store and forward mode. The entire frame is checked for errors and
any frames with errors are automatically filtered and will not be forwarded to the destination port.
Other features include port monitoring and broadcast storm throttling.
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