Inner Workings of WANPIPE

WANs, by their nature, are quite complicated. There are usually several players, including one or more Telcos, often a public network provider and often a separate ISP that adds to the confusion. The inevitable line teething problems and ongoing line debugging can often denigrate into futile finger-pointing exercises.

For this reason, a major part of the WANPIPE development has been devoted to debugging. Sangoma's philosophy is to provide customers with enough debugging information so that the customers can solve most problems by themselves. Furthermore, if support is necessary, Sangoma tech support must have enough information to solve the problem remotely.

Each WAN protocol has its own debugging utility that is used to determine the status of the driver and physical line, obtain protocol state and statistics, as well as raw and interpreted line traces. The data transfer involved in the monitors is UDP-based. Remote systems can be debugged via the Internet, without logging into the user system, while system security can be tightly managed. UDP calls are OS-independent, meaning that a remote Linux machine can debug a WANPIPE card running in a FreeBSD or Windows machine.

Since system security is an important issue, the UDP debugging commands can be turned off by setting the UDPPORT to 0, or better yet, by setting the TTL (time to live) value to a small one. By setting the TTL value to one, for example, only users that are logged into the machine or located in front of the first router will be able to operate the debugger. The TTL and UDPPORT values are configurable in the WANPIPE configuration file.

A current list of monitors and typical commands is given in Table 3. Under Windows, X and other graphic environments, the complicated command lines are replaced by simple GUI applications.

Table 3. Monitors and Typical Commands

The driver receives management requests via the UDP/IP stack. All received requests are then forwarded into a low priority queue. A low priority thread handles requests and sends the results back up the stack, to the originating IP address. UDP debug requests can also come from the network where the request is sent back through the line. Management connections through the network interface are treated differently from traffic from “above”. Only statistics are available through the network, while access from above allows the user to also reconfigure, test and set up the CSU/DSU and run line traces.

The proc file system is a memory mapped virtual directory structure that is used to provide driver and kernel information. Management systems, such as SNMP, use the proc file systems to obtain kernel/driver statistics and states. The WANPIPE driver binds into the proc file system by setting up /proc/net/wanrouter directory. This directory contains virtual files for each WANPIPE device. WANPIPE configuration and statistics can be obtained by reading/opening supported /proc files. To display tx, rx and error statistics for, say, the wanpipe1 device, use this command: cat /proc/net/wanrouter/wanpipe1

All WANPIPE events are logged via the syslog dæmon, in the /var/log/messages file. Note, syslog can be reconfigured to forward messages to a different location. To view the messages log continuously, execute: tail -f /var/log/messages.