AL3000 Advance Information
2/2000
Reference Only / Allayer Confidential
2
AL3000 Overview
The AL3000 provides all the necessary functions to implement IP Routing and Network
Management for the RoX-II bus based Fast Ethernet and Gigabit Ethernet Switching System. The
AL3000 is designed to interface to the Motorola PowerPC 800 Series, although the AL3000 could
easily interface with any 32-bit microprocessor (non-PCI bus) with glue logic.
The AL3000 integrates high performance IPv4 Routing/Switching and Network Management
engines. These engines perform the following major functions:
Routing Engine
•
Four Quality of Service (QoS) Queues that support programmable weighted
round-robin or strict priority to feed high-speed L3/L4 search engines
•
IPv4 parser that classifies the frames and processes IP exception handling
•
Routing Table Search function that performs L3/L4 search supporting 131,000
route entries, performs route table aging and maintains usage counters
•
IP Field Replacement function that performs L2/L3/L4 field replacements and
re-calculates L3/L4 checksums
•
IP Route Trace function that provides frame header information to the CPU
Network Management Engine
•
Provides MAC services for the CPU to transmit and receive Ethernet frames to
and from the RoX-II bus via high-speed DMA channels
•
Gathers the MAC address updates in real-time for Bridge MIB support
•
In conjunction with RoX-II bus Ethernet switch devices, provides Spanning-
Tree support
•
Provides access to all the internal registers of the RoX-II bus switch devices and
their associated PHY devices
•
Provides Ethernet related (EtherType), PHY related, and RMON MIB network
statistics counters (48 counters per port)
The Routing Engine in the AL3000 pulls frames from RoX-II bus based switching devices, such as
the AL126 or AL1022, according to the four priority queue control rules, and queues them to the
search engine. Network Management and other trapped frames (such as BPDU, GARP, etc.) are
directly queued to the CPU DMA. If a route entry is found, then all frame modification functions for
IP routing are performed by the Field Replacement function. Once fields are replaced, all L3/L4
checksums are updated, TTL decremented, and a new L2 FCS value is generated.
As a frame is routed, a frame header (first 64 bytes) can be sent to the CPU through a DMA channel
for Router management or diagnostic applications. Once a frame is routed, it is queued to one of the
output ports of the RoX-II bus switching devices, and transmitted according to the new QoS priority
classification. Routed frames can also be sent to the CPU for forwarding to the WAN.
The AL3000 provides access to all registers and MAC address tables on RoX-II bus switching
devices via remote register access commands. The AL3000 also provides all the network statistic
counters to support RMON groups 1 through 4 (EtherStats, History, History Control, Alarm) as well
as Ethernet-like MIB.
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