Web Cache Communication Protocol

Protocol Versions

• Only a single router services a cluster of systems
• Supports HTTP traffic flows only
• Provides generic routing encapsulation to prevent packet modification
• Routers and cache engines communicate to each other via a control channel based on UDP port 2048

• Allows for use across up to 32 routers
• Supports up to 32 engines/accelerators
• Supports any IP protocol including any TCP or UDP
• Supports up to 255 service groups
• Adds MD5 shared secret security

Primary WCCP functions

Registration

• Accelerator or Engine is a WCCP client
• * Registers WCCP services with “Here I Am” if application is operational
• * Registration announces WCCP client on service group, provides availability notification, requests interesting traffic
• * Transmits “Here I Am” every 10 seconds
• * Lead WCCP client instructs routers on protocol/port, assignment, forwarding, and return methods
• Router is a WCCP server
• * Accepts service group registration
• * Acknowledges “Here I Am” with “I See You”
• * Waits 30 seconds before declaring engine failed
• * Announce engines to other engines
• * Router id is highest interface IP or highest loopback IP if one exists
• * Redirects traffic to engine

Assignment

• Selects an engine in the cluster
• Hash 256 buckets
• Mask 128 buckets represented by 7 bit mask of the source or destination IP/Port

Redirect from Router to Cache Engine

• Redirect list allows router to permit/deny traffic to intercept
• Two methods of redirection:
• * WCCP L2: Local subnet only, little overhead. Rewrites packet MAC address to that of the local Engine
• * WCCP GRE: Any IP-Subnet, more overhead. Creates tunnel from router to local or remote Engine.

Return from Cache Engine to Router

• WCCP GRE return.
• WCCP L2 return.
• Engine can optionally return traffic any other way including routing.

Products that implement WCCP

• ASR 1000 Routers
• Application & Content Networking System
• Wide Area Application Services
• ASA/PIX Firewalls
• Some IOS versions
• IronPort S-Series Web Security Appliance
• Nexus 7000 Switches