Network Troubleshooting: An In-band Approach

Users and operators of communication networks must be able to quickly diagnose (i.e., detect and locate) network faults. The large body of sophisticated network diagnosis tools used are typically “out-of-band”: they introduce a stream of probes that are separate from the data traffic experiencing a network fault. Out-of-band techniques only collect information about the network conditions at the time the tool is running, so they may fail to capture transient faults entirely. Also, the measurements may experience very different behavior than the data traffic that is actually subject to the network fault. To make matters worse, probing tools introduce additional traffic that may itself alter network conditions. We propose a complementary technique, which we call in-band network path diagnosis (INPaD). The basic idea is simple: include information associated with network faults in the data packets themselves. Since INPaD approaches embed information on network conditions in the data stream itself, they can directly record the symptoms of even transient faults without the overhead of regular probing. We have developed Orchid which is a specific INPaD scheme and evaluated Orchid on VINI[1].