SenderID characters

What is the maximum number of Characters that can be accepted as the Sender IDs for Alphanumeric SMSes?	The max length of sender ID Toku’s SMS gateway supports is 21 characters as per SMPP 3.4 standards
What are the common and acceptable symbol?	All characters in the ASCII table are supported, which include all the special characters in the reference list from SGNic.
What are the unacceptable symbols, and how are they been handled	Our system will reject messages that uses sender IDs outside the regular ASCII table