====== Case Sensitivity in SIP ======

^ Element     ^ Case Sensitive? ^
| Via branch  | insensitive (token) |
| Call-ID     | sensitive - Byte for byte compare |
| SIP-Version | insensitive - must send uppercase though |
| Header field names | insensitive |

From RFC 3261, sect 7.3.1:

When comparing header fields, field names are always case-insensitive.  Unless otherwise stated in the definition of a particular header field, field values, parameter names, and parameter values are case-insensitive.  Tokens are always case-insensitive.  Unless specified otherwise, values expressed as quoted strings are case-sensitive.