Having concerns with my macbook's network performance, I decided to check out networking activity. I noticed a huge volume (1.5gb) of sent packets for safari networking even though I am not doing any file uploads through safari or any application for that matter.

In the process, I noticed a stack branching from 'DispatchQueue com.apple.CFNetwork.connection with the descriptor '???'.

Out of curiosity, what is this and is it an indication of some networking error. From my limited understanding CF network handles receiving HTTP request types and headers. Would these threads just indicate errors in acquiring HTTP requests for a certain site.

Attached an image for reference: '???' stack descriptor

  • 1
    I think that just means you don't have the compiler symbols for CFNetwork, so the backtrace can't tell you the symbolic (i.e. human-readable) name for the functions at those addresses. It's common for symbols to be stripped from closed source binaries so it's harder to reverse-engineer the proprietary code.
    – Spiff
    Mar 21, 2023 at 5:13
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    Also, those aren't subthreads, that's a call stack from a single thread.
    – Spiff
    Mar 21, 2023 at 5:16
  • One more thought: If you were doing audio or videoconferencing from your browser, like Google Meet or something, that would probably show as lots of data being sent by your browser even though it's not a file upload, it's an upstream audio or video stream.
    – Spiff
    Mar 21, 2023 at 5:20
  • Perfect thanks Spiff, explains this. And silly I didn't think of video conferencing**
    – N S
    Mar 21, 2023 at 5:37

1 Answer 1


As noted by @Spiff in the comments, the '???' descriptor for the stack is such because the system wouldn't have the compiler symbols to make the functions human-readable.

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