IP Interconnection among service providers is significantly increasing as the Transition of the PSTN from SS7/TDM to SIP/IP networks progresses. Practical deployment experience in the core carrier networks has exposed operational and implementation differences in the way IP for SIP traffic works ‘on the wire’. These differences complicate interconnection, and in some cases require ‘protocol normalization’ to achieve full interoperability. Time and effort is required to document the differences and configure the SBC or I-CSCF proxy to implement the necessary changes to the on the wire protocol.
In addition, there is no commonly agreed methodology on how to translate E.164 numbers for routing data for IP SIP interconnections, although DNS based ENUM [RFC 6116] technologies have been deployed widely in private networks.