See follwoing table:
| Asterisk/Trixbox | SER | OpenSER | |
| SIP protokol | yes | yes | yes |
| NAT Traversal | no | yes | yes |
| RTP Relay | yes | yes | yes |
| IPv4 | yes | yes | yes |
| IPv6 | no | yes | yes |
| ENUM | yes | yes | yes |
| Digest Auth | yes | yes | yes |
| ACL | yes | yes | yes |
| Accounting | yes | yes | yes |
| MySQL driver | yes | yes | yes |
| LDAP | yes | yes | yes |
| Call forwarding/transfer | yes | yes | yes |
| Call parking | yes | no | no |
| Caller ID | yes | yes | yes |
| IVR | yes | SEMS | SEMS |
| Macros | yes | no | no |
| Music on whatever | yes | no | no |
| Open Settlement Protocol | yes | yes | yes |
| Protocol conversion | yes | no | no |
| Transcoding | yes | no | no |
| Trunking | yes | no | yes |
| Voicemail | yes | SEMS/* | SEMS/* |
SEMS – with use of SIP Express Media Server SEMS/* – or Asterisk