ISPPlanet Cache Review Series - CacheFlow 545

Designing Your Cache Network
All CacheFlow products can operate as simultaneous forward, transparent, and reverse proxies. CacheFlow provides detailed, product-specific instructions for transparent redirection using L4 switches from Alteon, ArrowPoint, or Foundry, Cisco routers with WCCP v1 or v2, or Bay routers with packet filters. We did not spot documentation describing reverse proxy install considerations. We tested the 545 in forward proxy mode only, since our evaluation unit included just one Ethernet.

CacheFlow offers more client browser assistance than most products. In proxy mode, browsers must be reconfigured to redirect HTTP to the cache. Configuration can be performed manually or automated with a PAC file. The CacheFlow GUI assists with PAC file creation and presents step-by-step instructions (below, left) to guide end users through browser configuration. A default PAC file redirects HTTP and HTTPS to the CacheFlow's proxy port. This file can be customized; for example, to cache FTP and bypass specified target URLs (below, right) .

CacheFlow offers three alternatives for workload distribution in a cache hierarchy: simple forwarding, advanced forwarding, and ICP forwarding. Simple forwarding just redirects missed requests to a primary or alternate Gateway (right). The gateway can be any other cache, since there is no inter-cache protocol involved. A Direct / Deny list can be used with simple forwarding to deny (block) requests or avoid redirection for selected IP addresses and subnets.

Advanced Forwarding designates "Forward Hosts" as default or backup, and organizes them into groups. Missed requests are balanced across each group; hashing ensures that each object is always requested from the same member. Requests that satisfy a URL regular expression, domain name, or IP address/mask can be forwarded, sent directly to the origin server, or denied.

Finally, hierarchies can use ICP for more efficient communication between parent, peer, and child. Like Advanced Forwarding, ICP Forwarding can be bypassed or denied by domain name and IP address. However, ICP allows a child to simultaneously check all siblings and parents; only if the content cannot be located will it be retrieved by one parent.

There are no CacheOS mechanisms for clustering into high-availability configurations. Instead, CacheFlow recommends that multiple caches be used in transparent mode for redundancy and load balancing. CacheOS 2.2.07 (a maintenance release scheduled for late January) will allow a cache with multiple interfaces on the same subnet to "fail over" if the adapter used to reach the default gateway goes down.

Introduction/The Platform	Predictive Caching
Four-Step Setup <	Controlling Cache Services
Designing Your Cache Network	Viewing Cache Performance
> Managing the CacheFlow	Advanced Monitoring
Balancing Simplicity vs. Volume	Product Support/Final Thoughts