Codec
G.711
G.726
G.729
Sample Rate (ms)
10
20
30
40
50
60
Layer 2 Protocol
PPP
Frame Relay
MPLS
L2TP
GRE
Ethernet
Ethernet w/ 802.1Q
IP Header Compression
No
Yes
RTP Header Compression
No
Yes
Security
None
IPSec w/ AH
IPSec w/ ESP
Cisco GET
Number of Simultaneous Calls