Packet Processors
Packet processors are used to deliver the required level of processing power in applications where the host processor cannot provide sufficient performance. Some packet processors are embedded directly on the network card, while others are more like host processors that provide dedicated processing power for each interface.
Embedded Packet Processors
An embedded packet processor is typically used with a fixed configuration network card to provide what might be called a "one-trick pony." Embedded packet processors are most commonly used when an application always requires additional processing power. When an application always requires adjunct processing, it is usually more economical to put the dedicated processor and the network interface together on the same board.
ImageStream offers a number of interface cards that include an embedded packet processor. Some of these cards provide processors for VPN encryption/decryption, ATM cell processing, small packet processing, and ethernet switching.
High-speed ATM cards provide an excellent example of network cards that require an embedded packet processor. The ATM SAR chip is used to coalesce inbound ATM cells into larger packets, to break up large packets into ATM cells for transmission, and to manage ATM quality of service (QoS).
The ImageStream 720 series includes adapters with embedded packet processors. These cards include a dedicated Intel i960 processor that coalesces packets to make it possible for the host to process over 45 Mbps of full duplex data with average packet sizes as small as 64 bytes. Other adapters that provide an embedded packet processor include ethernet cards with VPN encryption processing, and embedded ethernet switches.
Modular Packet Processors
Modular packet processors are designed to provide a dedicated packet processing "blade." The processor blade is usually a CompactPCI single board computer (SBC) that can be loaded with different PMC network modules. This kind of dedicated packet processor is designed for high-demand systems that require distributed processing to move data through the system at full speed.
Modular packet processors are totally programmable. Each processor runs its own complete operating system. It can can be customized to work with a specific network module, or generalized to work with a wide range of network modules.
Modular packet processors can be used to build a completely distributed processing system. Although a system like this has a central host processor, the host processor is used to store common data required by all packet processors, and to manage the other packet processors in the system. A distributed processing topology like this is commonly used in systems that must feed high-speed switch fabrics with large volumes of streaming data. It is also an ideal topology for VPN applications that require a large number of high-speed encrypted network interfaces.
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