"If you work with IP telephony, it's quite possible that you have not heard about OpenSER, but certainly you must have heard about Asterisk. Well, I love a polemic headline and I have seen this question asked in the forums many times. So, I will dare to compare these two very popular softwares dedicated to the VoIP market. The idea here is not to show you which one is the best, but mainly how they are different from each other. Below is a comparison topic by topic.
"Asterisk is a Back to Back User Agent (B2BUA), while OpenSER is a Session Initiation Protocol (SIP) Proxy. This makes all the difference between them. The SIP proxy architecture is faster than a B2BUA because it deals only with signaling. On the other hand, the B2BUA architecture, even being slower, handles the media and it is capable of several services not available in a SIP proxy such as Codec Translation (that is G729<->G.711), Protocol Translation (SIP<->H323), and services related to media such as IVR, Queuing, Text to Speech, and Voice Recognition..."
