IP Communications and Services for NGN

SIP Security ◾ 199

proxy server can accommodate. is includes all the processing that the proxy per-

forms for a call, from its setup to its termination or teardown. e two rightmost

columns are the most important ones; they report the throughput values converted

into relative processing cost. In the first row, a reference value of 100 has been

assigned to procedure/scenario (5). e results show that the introduction of SIP

security accounts for nearly 80 percent of the processing cost of a stateless server

and 45 percent of a stateful server. is increase can be explained with the increase

in the number of exchanged SIP messages and with t