The 4621SW IP Telephone is based on the 4620SW with the same housing, feature buttons and software along with an enhanced backlit display. The 4621SW also supports the new EU24BL (back lit expansion module) and also includes a 2 port Ethernet switch. A new phone, the 4621SW will replace the 4620SW. The 4621SW can run either the H.323 protocol, for integration with traditional Avaya IP Telephony Servers and Gateways, or the SIP protocol, for support of SIP Communications Servers such as the Avaya SIP Enablement Services (SES) Rel 3.0 Solution.