Proxy / Port
The Proxy and Port fields are optional fields allowing you to specify the address of a HTTP proxy to use for all web traffic over this connection. Carriers sometimes use HTTP proxies to modify websites for your device, or to improve the speed of commonly access web pages and resources by caching them.
It's relatively rare for a carrier to require that you use an HTTP proxy for your connection. In addition to this, many carriers use HTTP proxies that don't even require this field to be set, known as transparent proxies.
The first field specifies the address of the proxy server. This may be given as an IP address (for example, numbers connected with dots or colons such as 10.0.0.1), or as a hostname.
As always, consult your carrier's recommended APN settings to see whether they recommend that you add the address of their proxy server into this field. Many carriers won't use or require a proxy, meaning this setting should remain empty.
This field relates to the above Proxy field, and if a proxy is being used, both must be set. There is no default value for this field, and leaving it blank will disable use of the proxy.
Consult your carrier's recommended APN settings to see what port number you need to use if you are using an HTTP proxy. If you do not need to use an HTTP proxy this should remain empty.
If you don't know which port use, you may try some common ports. Common port numbers for HTTP proxies may include 80, 3128, or 8080.