Call trace is an enhanced debugging feature that allows control plane messages for a single session to be monitored. When call trace is enabled, all protocols related to this session are captured. Operators can use this information to easily debug entire problematic sessions instead of debugging and verifying separate protocols such as DHCP, ARP, or RADIUS.
Call trace also logs some events that are not directly associated with a protocol, such as LUDB access.
Call trace can present the captured packets for further processing in one of the following ways:
Call trace can send the captured packets as live output over a UDP tunnel to an external monitoring device.
Call trace can store the captured packets as PCAP on a pre-provisioned compact flash. If the system already uses the compact flash intensively, such as for ESM persistency, then this method is not recommended for use in a live network.
Call trace can display decoded packets in debug output. This method is mainly for use in low-scale debugging of a few sessions; use on large-scale live networks may impact overall performance.
Generated traces contain the original packets, encapsulated in a custom header that contains metadata. To decode the metadata and extract the packet, a Nokia-specific Wireshark plug-in is required. Contact the Nokia Technical Assistance Center (TAC) for information.
In general, call trace does not include packets that are common between sessions. Where it is necessary to indicate failure or progress, an event is generated. This is done to guarantee consistency between session traces, independent of timing or session setup order. For example, for PPPoE LAC sessions, L2TP tunnel setup messages are not reflected in call trace, but an event is generated to indicate whether an L2TP tunnel was set up successfully. Subsequent L2TP session setup messages are traced in context of the PPPoE LAC session.
When storing call trace results on a compact flash, files are not automatically synchronized to the standby CPM.
Call trace distinguishes between traces and trace jobs. A trace consists of a set of matching criteria and additional parameters such as a trace profile and a name. Each session that matches a trace creates a trace job if system resources are available. Trace jobs can either be stopped individually or by removing the original trace. By default, existing sessions do not create a trace job when a new trace is enabled; this functionality must be explicitly enabled.