Switching to VoIP

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Chapter 10: Security and Monitoring

dmesg’s output is flat text that you can redirect to a file. Suppose you wanted to iso-

late the traffic prefixed with Chicago into a file by itself:

# dmesg | grep Chicago >chicagoVoIP.txt

Or better yet, email that log to somebody, perhaps so they can import it into a

spreadsheet for further analysis. In the following example, pressing Ctrl-C will stop

the dmesg application and an email will be sent containing the Chicago entries:

# dmesg | grep Chicago | mail [e-mail]

SNMP

Simple Network Management Protocol is a lightweight method of collecting traffic

and performance data from network devices such as servers and switches. Different

kinds of data use different parameter schemas, called management information

bases, or MIBs. MIBs define how SNMP refers to metafields specific to a certain kind

of data, such as Ethernet traffic or DNS-lookup statistics.

MIBs exist for SIP (http://www.iana.org), VOCAL (http://www.vovida.org), MEGACO

(http://www.ietf.org), and other VoIP technologies. There are some useful VoIP-related

SNMP monitoring tools (OpenNMS, Multirouter Traffic Grapher, etc.) that can be

customized to make use of these MIBs, too. There isn’t yet a fully integrated SNMP

MIB for Asterisk, though, which leaves Asterisk administrators ...