Caching router / firewall
The art of caching system traffic without needing individual / browser side setting.
What is transparent caching?
Transparently proxying / caching system traffic without requiring user configuration or expertise. A method to simplify caching for the end-user Causes all users to make use of the cache.
Why use transparent caching? ď Ź
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Simplicity of use. No setup expected by the end-user. Catching all people. No users could avoid the cache.
What is involved?
TCP stage routing Slow NAT or related engineering to hijack port 80 traffic. A Private proxy with some understanding of transparent proxying A cache
Tools available
TCP stage Routing
Plan routing / course maps
TCP / layer 4 switches
with or without NAT
Cisco WCCP
Host-Level NAT
Linux firewall signal
FreeBSD firewall code
IP-Filter
Using policy routing to redirect traffic ď Ź
A standard router configured to route TCP port 80 to the cache private proxy server.
Internet
User 1 User 2 User 3 User ..
Policy routing (cont.)
Rewards Could generally be implemented without additional equipment
Drawbacks
Only static routing
No-Fault tolerance. Port 80 traffic disrupted if cache machine fails. More CPU load on the switch
Running the cache on a router ď Ź
Small network / firewall. Host used as router with private proxy provider. Router / Cache Server
Internet
User 1 User 2 User 3 User ..
Caching router / firewall
Rewards Could generally be implemented without additional equipment
Drawbacks
Only static routing
No-Fault tolerance. Port 80 traffic disrupted if cache machine fails. More CPU load on the switch
Cisco Web Cache Control Protocol (WCCP)
Produced by Cisco for Cisco Automated setting. Their presence is announced by private proxy cheap servers to the switch.
Load balancing
Fault recovery
Commercial Licensing needed. Not currently an alternative for free software.
TCP switch benefits
May bypass the cache if it fails
Superior stability
Can distribute force on multiple cache servers
Can-Do the NAT, enabling the use of any OS on the cache server. Some do HTTP proxy translation, allowing the utilization of any proxy application.
TCP switch drawbacks ď Ź ď Ź
Yet another pricey box to get Utilizing NAT requires change dealer support in the application to support old browsers with premium private proxies.
Problems related to request formats
A transparent proxy should reconstruct the URL of the request. Host: headers not always accessible. HTTP/1.1 characteristic or 1.0 add on. INTERNET protocol address from NAT translation.
What happens at the TCP level?
Usual connection / proxying
IP-BASED routing
TCP is end-to-end
One IP-ADDRESS, one Host
Transparent best private proxy services
TCP based routing
TCP isn't any longer end-to-end
One IP address, “multiple hosts”
Problems at the TCP level
TCP typically depends on two IP practices. TCP and ICMP. Of those only TCP could be reliably redirected. ICMP is necessary for Path MTU discovery. TCP resets in case a single package moves another path skipping the redirection.
Things to consider when configuring OS level NAT ď Ź
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Try not to interrupt traffic to/from the cache server host. Be sure that the traffic is not redirected back once again to the cheap proxy. Anticipate to do packet level records, ultimately from the separate container.
Recommended steps when building a transparent proxy
Think it over. Is it really required?
Assemble and test the proxy server
Configure NAT to the proxy-server
Test drive it utilizing a local LAN consumer
Setup TCP degree routing.
Common problems
Interaction hangs for many consumers Almost proxy service provides certainly brought on by MTU associated problems.
Link reset problems
Terrible efficiency
Probably Pc bottleneck in the router.
Summary ď Ź
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Transparent caching is an excellent device in most configurations to help relieve user side configuration. It's some important limitations. Not a total replacement common proxying. For the same goals are achieved by many automatic instructions on how to configure proxy settings.
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