The following classes are available as a part of the SIP Codec API:
CSIPAcceptContactHeader, CSIPAcceptEncodingHeader, CSIPAcceptHeader, CSIPAcceptLanguageHeader, CSIPAddress, CSIPAddressHeaderBase, CSIPAllowEventsHeader, CSIPAllowHeader, CSIPCallIDHeader, CSIPContactHeader, CSIPContentDispositionHeader, CSIPContentEncodingHeader, CSIPContentTypeHeader, CSIPCSeqHeader, CSIPEventHeader, CSIPExpiresHeader, CSIPExtensionHeader, CSIPFromHeader, CSIPFromToHeaderBase, CSIPHeaderBase, CSIPParameterHeaderBase, CSIPPAssociatedURIHeader, CSIPProxyRequireHeader, CSIPRAckHeader, CSIPReferToHeader, CSIPReplyToHeader, CSIPRequireHeader, CSIPRetryAfterHeader, CSIPRouteHeader, CSIPRouteHeaderBase, CSIPRSeqHeader, CSIPSecurityClientHeader, CSIPSecurityHeaderBase, SIPStrings, CSIPSubscriptionStateHeader, CSIPSupportedHeader, CSIPTimestampHeader, CSIPToHeader, CSIPTokenHeaderBase, CSIPUnsupportedHeader, CSIPUnsignedIntHeaderBase.