CISCO-CASA-FA-MIB
This MIB module in conjunction with the CISCO-CASA-MIB, defines the SNMP management information base for managing the Cisco Appliance Services Architecture (CASA) Forwarding Agent. The following is a set of definitions used in the rest of the MIB. CASA is a protocol allowing software entities (called Appliances, examples are web caches, firewalls, load balancers) to control the behavior of network hardware devices (called Forwarding Agents, examples are switches or routers) by providing a set of rules used to handle network traffic. A Network Appliance (referred to as an Appliance) is any subsystem whose purpose is to provide a specific additional value-added service to the network device, and could be implemented as a standalone box, a line card or processor card, or a software subsystem. Examples of Network Appliances would include Load Balancers, WebCaches, and Firewalls. An Appliance tells Fowarding Agents how to handle packets based on their source and destination IP addresses and ports, and IP protocol fields. This set of information is called an Affinity. A Service Manager is an Appliance that requests packet flows from Forwarding Agents through CASA. A Real Server is a physical computing engine or part of that physical computing engine that offers one or more application services to a set of clients in the network. A packet flow is a TCP connection or a sequence of UDP packets between a client and a specific Real Server, pertaining to a specific application. Flows are represented by entries in the affinity cache tables. The Service Manager requests packet flows from Forwarding Agents by sending Affinities which contains wildcards on some of the Affinity fields. Affinities that contain wildcards in some of the fields are called Wildcard Affinities. The Service Manager may send the Forwarding Agent an Affinity containing explicit values for each of the fields. These Affinities are called Fixed Affinities. Typically Wildcard Affinities are used to instruct the Forwarding Agent to send packets received by the Forwarding Agent, which match the Wildcard Affinity, to the Service Manager. When the Service Manager receives the matching packet, the Service Manager typically will send the Forwarding Agent a Fixed Affinity. The Forwarding Agent uses Fixed Affinities to match packets coming from the network, execute any processing required on that packet, and forward that packet to a destination IP address (designated in the Fixed Affinity) called the Dispatch Address. When an IP packet arrives at the Forwarding Agent, the Forwarding Agent attempts to match the packet with the Fixed Affinities in the Fixed Affinity cache. If there is no match, an attempt is made to match the packet with the list of Wildcard Affinities. If there is no match the packet is routed normally. If there is a match with a Wildcard Affinity, the Forwarding Agent sends the packet to the Service Manager who will send the Forwarding Manager a Fixed Affinity which provides information on how to process IP packets similar to the one received by the Forwarding Agent. Processing of such packets may include sending the packet to the Service Manager. Such packets are called Interest Packets. Alternatively a Tickle Packet may be sent to the Service Manager which is an indication that a matched packet has been received by the Forwarding Agent. Reference: [1] Cisco Appliance Services Architecture (CASA) document. [2] CISCO-CASA-MIB. Diagram showing Forwarding Agents, Service Manager, Real Server and clients. ______ ______ ______ (Real ) (Real ) (Real ) (Server) (Server) (Server) (______) (______) (______) | | | +---------------+ | | | |Service Manager|-+----------+--------------+ | +---------------+ | | | | | ++---------+ ++---------+ ++---------+ | F. Agent | | F. Agent | | F. Agent | +----------+ +----------+ +----------+ | | | ___|_________________|______________|__ ( ) ( N E T W O R K ) (_______________________________________)