What does a NACK or NAK log entry indicate?
Negative Acknowledgement
PCoIP imaging will acknowledge or use selective acknowledgement in newer PCoIP implementations, to signal to the PCoIP Host that imaging data was successfully received and displayed. In the event that this process is not successful, a negative acknowledgement will be sent to the PCoIP host and logged in the firmware logs or PCoIP server log files.
These NAK entries indicate the reason for the negative acknowledgement and what was lost. In older log files, NAK entries maybe NACK. The imaging system will then intelligently determine if the data needs to be retransmitted. Conditions that cause too many NAKs will trigger an imaging reset. On a PCoIP Software Client the image will pause, on a PCoIP Zero Client this will cause a momentary black screen.
NAK LOSS
Newer PCoIP Server logs from the HP Anyware PCoIP Agent will contain information such as
LVL:2 RC: 0 IPC :NAK LOSS for disp 0 fsp 3 f_seq 0, 0. (ar 1 mra 0) recode from scratch
This entry indicates that the PCoIP Client imaging controller signalled that imaging data was lost in transit. This can indicate network issues. How to identify network issues in PCoIP Logs network issues.
Other NAK reasons may include NAK CACHE and NAK DECODE.
The information contained after the NAK LOSS indicates what was lost. This is not necessary to understand to troubleshoot the underlying reason for the NAK. This information maybe used by Teradici Engineering for deeper analysis.
Older PCoIP firmware logs may contain
0d,00:04:07.110> LVL:2 RC:-500 MGMT_IMG :nack c:5 d:1 f:c r:6f, ptr 52. 0d,00:04:07.240> LVL:2 RC:-500 MGMT_IMG :nack c:5 d:1 f:2 r:7d, ptr 5c. 0d,00:04:07.400> LVL:2 RC:-500 MGMT_IMG :nack c:5 d:1 f:8 r:52, ptr 6a. 0d,00:04:07.470> LVL:2 RC:-500 MGMT_IMG :nack c:5 d:1 f:8 r:53, ptr 6f. 0d,00:04:07.470> LVL:2 RC:-500 MGMT_IMG :nack c:3 d:1 f:8 r:54, ptr 70.
c: command.
- Packet loss is 5,
- Bad decode is 4,
- Bad reference is 3. A bad reference will often follow a packet loss and indicates that one or more packets were lost within an imaging slice.
d: display. 0 or 1.
f: frame slice position (0 to 63).
r: ref id, used internally for debug
ptr: buffer index
NAK REF
A NAK REF indicates a previous imaging block is missing. A NAK REF is usually preceded by other NAK messages that indicated missing imaging data and are a consequence of the PCoIP Client not having imaging data the PCoIP host has already transmitted. A NAK REF may or may not result in imaging data being re-transmitted.
LVL:2 RC: 0 IPC :NAK REF for disp 0 fsp 12 f_seq 0, 3. (ar 1 mra 0) recode from scratch
NAK CACHE
A NAK CACHE indicates that there was an imaging cache miss on the PCoIP Client.
LVL:2 RC: 0 IPC :NAK CACHE for disp 0 fsp 12 f_seq 0, 6. (ar 0 mra 0) recode from scratch
These messages are not of concern unless they are resulting in imaging resets.
NAK DECODE
A NAK DECODE indicates the PCoIP Client was unable to decide PCoIP imaging data. If this message is appearing frequently and is resulting in a poor PCoIP experience, ensure you have updated to the latest PCoIP Firmware and HP Anyware PCoIP Agent. If this does not resolve the issue, open a ticket with Teradici Global Support Services. If possible, provide the video, web page, image that is causing this to happen to allow reproduction of the issue.
NAK PACKET
A NAK PACKET is a warning message indicating that a number of packets went missing on the network, and unless successfully re-transmitted and received by the client, will ultimately lead to a NAK LOSS. It permits the Agent side the ability to pre-emptively re-encode pixels (or not issue a build) – but in most cases, is merely a warning that a LOSS is inevitable.
See also: