Highly scalable architecture for application network appliances

A method comprising:

• at a network device, receiving packets of a network transaction from a client device over a first network for accessing a server of a data center having a plurality of servers over a second network;
• processing at a first service module of the network device a first portion of OSI (open system interconnection) compatible layers of network processes on the packets;
• and
• processing at a second service module of the network device a second portion of OSI compatible layers of network processes on the packets, wherein the first portion includes at least one layer that is not included in the second portion.

A machine-readable storage medium having instructions stored therein, which when executed by a processor, cause the processor to:

• receive packets of a network transaction at a network device from a client device over a first network for accessing a server of a data center having a plurality of servers over a second network;
• process at a first service module of the network device a first portion of OSI (open system interconnection) compatible layers of network processes on the packets;
• and
• process at a second service module of the network device a second portion of OSI compatible layers of network processes on the packets, wherein the first portion includes at least one layer that is not included in the second portion.