• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 40 subscribers
  • Views 1037 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC3120MOD: Default TCP recv window size

TobiasR
Prodigy 100 points
Part Number: CC3120MOD
Other Parts Discussed in Thread: CC3120, CC3100MOD, CC3100

Hello,

I am curious whether the default TCP recv. window size is identical for the CC3100MOD and the CC3120MOD? With almost identical software (just the driver for the CC3120 is different / other SDK) I get rather no retransmissions on the CC3100MOD but a lot of those on the CC3120MOD. 

I am sending roughly 11 packets / second from CC device acting as TCP server and AP to my PC. Average length of those packets is 1100 bytes.

The retransmissions are always preceeded by a TCP package sent from CC3120 which is identified as [TCP previous segment not captured] in wireshark. After this there is always a burst of four TCP Dup Acks followed by several single Dup Acks until TCP fast retransmission is initiated.

Setting the windows size to 300 bytes seems to have an effect but is not producing the same behavior as on the CC3100. What could be the cause of this?

Thanks!

  • 0
    TI__Mastermind 35070 points
    Hi Tobias,

    How are you setting the window size? The API sl_Recv allows the user to to specify how large the receive buffer is.

    Can you send the wireshark logs?


    Regards,
    Toby
  • 0 in reply to Toby
    Prodigy 100 points
    Hi Toby,

    I am setting the window size with this API call:

    SlSockWinsize_t size;
    size.Winsize = 3000; // bytes
    sl_SetSockOpt(SockID,SL_SOL_SOCKET,SL_SO_RCVBUF, (_u8 *)&size, sizeof(size));

    sl_Recv is not critical in this case as the CC31XX device is rarely receiving data from my PC, it is sending rather.

    I guess I can recreate the wireshark logs, where shall I send them?

    Regards
  • 0 in reply to TobiasR
    TI__Mastermind 35070 points
    I've sent you an E2E friend request. You can send the logs there, or you can insert it as a file in your reply to this post.

    I'll reply with a followup once I've received the logs and looked at them.