Monday, August 29, 2011
Today’s topic is logging. In theory, you would never need it. However we all know from the real life, that when things go not the way they should, it is good to have some help from the device. That’s why the m9 comes with a powerful logging subsystem. You can see the log easily from the web interface, there is one page where you can set the log level and there is another page where you can see the log messages.
In the snom desktop phones, there is just one flat log level. If you turn log level 9 on, you get flooded with messages. They may include what you need, but you have to be quick to get them out of the system and you have to spend some extra time to get them out. Because if this, on the snom m9, we split the log up into different categories:
· General events: All other events that do not fit into any of the other categories.
· Media-related events: Events coming from the media subsystem, for example RTP related messages, SRTP decoding problems.
· SIP registration messages: Everything that has to do with the SIP registration. Not only the SIP messages, but also the routing of those messages, refresh intervals and so on.
· SIP call messages: Everything related to the SIP call. As with the registration, not necessarily only the SIP messages, but also other stuff associated with a call.
· Other SIP messages: All other SIP messages, for example subscriptions, instant messages.
· Web server events: The snom m9 has a built-in web server; in this log level you will see when someone logs in, when a session expires and so on.
· DNS events: DNS can be complicated, and there is a special log level for the DNS messages.
· LDAP events: Everything related to the LDAP client in the m9.
· DECT events: Events that have to do with the DECT subsystem.
· Network events: Events that are coming from the network subsystem, for example DHCP messages, LLDP, 802.1X messages.
· TLS: If you have problems with the TLS subsystem, those messages are in this log level. You can even increase the log level, so that you can see what secrets are being exchanged.
· ICE: The snom m9 uses ICE for some server types, and there can be specific problems in this area. That’s why we included a log level for this.
· ZRTP: If you are using ZRTP, you can see the related messages in this log level.
In each category, you can select between 0 and 9. 0 means that there are no messages being shown in this category; 9 means as much as possible. The m9 limits the total to around 100 KB; if the total content gets more than that, the m9 drops the oldest log entry. This makes sure that the m9 is not running out of memory because of logging.
Also we decided to make another change to the behavior of the snom desktop phones. The newest messages are at the top. This is simply because usually you are interested in the most recent messages, and you don’t have to scroll down the page to see them. The other change that we did is that the log messages are mixed with the SIP messages. This makes it a lot easier to see how the log messages relate to the SIP traffic. Having it in two different pages makes this job a lot more difficult.