implementing big5 over telnet protocol?

I've implemented a telnet client and one of the feature requests is to support big5 encoding. How is Big5 implemented over telnet, when only 7-bit character codes are 开发者_开发知识库supported? The Big5 "lead bytes" (0x81 to 0xfe) are all in the range above 0x7f reserved by the telnet protocol. Of course, if I took out VT100 escape code parsing and treated non telnet-escape-sequence bytes as plain big5-encoded text, that would probably work, but I don't know if that's the standard (if there even is a standard). Also, is there an equivalent to the VT100 terminal protocol for Big5 encoding?

FYI: This project is written in C# and runs on windows phone silverlight.

I think you want RFC2066, which describes the TELNET CHARSET Option.