Replay PCAP File

The XenaManager is capable of replaying the packets in a PCAP file on a single test port. You access this function through by selecting the Edit ‣ Replay File menu item when the port you want to use is selected. You will have to reserve the port before the function is available.

../_images/pcap_1.png — Fig. 190 Replay File function

When you select the Replay File menu item you will be asked to select the PCAP file you want to use. XenaManager supports both traditional PCAP files and the newer PCAP-NG format. After you have selected the PCAP file then content of the file is imported and a replay control windows will be shown (see screenshot below).

../_images/pcap_2.png — Fig. 191 Replay packets from a pcap file

Important

XenaManager assumes that the PCAP file you provide doesn’t include FCS checksum field. When doing the replay, XenaManager will append the 4-byte FCS checksum field to the replayed packets. Read Comparing Replayed with Original PCAP for more.

The following commands are available in the control window:

Table 61 PCAP Replay Commands
Command	Explanation
Start	Start transmitting packets form the PCAP file as fast as possible. When all packets are sent the replay is automatically stopped (unless the Loop Until Stopped option is selected).
Stop	Stop the packet transmission.
Single-Step	Send the next packet in the packet sequence and stop.
Loop Until Stopped	If selected, the transmission will start over when the end is reached. If not selected the transmission is stopped when the end is reached.
Rewind	Reset the current packet position to the first packet in the sequence.

Important

The following limitations apply to the PCAP Replay function:

Packets will not be re-sent with the original inter-packet timing from the PCAP file. The transmission control is handled by the PC running XenaManager. Packets are sent one at a time and the next packet is not sent until the last packet was successfully transmitted. The transmission timing is thus influenced by both network and Windows OS latency.

The maximum packet size that can be transmitted is 2 Kbyte.

Comparing Replayed with Original PCAP

When you capture packets in Wireshark on your computer, which is behind a NIC, the captured packets don’t include the FCS checksum. But when you capture packets on Xena test equipment, the capture is directly on the wire. This means, Xena test equipment captures everything on the wire, including the 4-byte FCS checksum field.

If you want to exclude the FCS checksum in the captured PCAP file, you should disable Option ‣ Save Ethernet FCS.

../_images/pcap_3.png — Fig. 192 Exclude Ethernet FCS checksum field in PCAP

After disabling Option ‣ Save Ethernet FCS, the captured PCAP will not contain the FCS checksum. In Wireshark, if you want to see the capture length instead of the length on the wire, you can add a field to the column as shown in Fig. 193.

../_images/pcap_4.png — Fig. 193 Add capture length field in Wireshark view