[time-nuts] wifi with time sync

Orin Eman orin.eman at gmail.com
Sat Jan 14 19:29:09 UTC 2017


I merely used the ping to demonstrate Wireshark's packet time stamping
(though in this case, it seems that the router responds immediately).
FWIW, a couple of NTP packets got captured too with a 34 ms round trip.  I
was actually looking for an ARP request/response in consecutive packets on
the grounds that the router wouldn't delay ARP responses... I found one and
it was (claimed) 1.107 ms round trip.  I make no claim as to the accuracy
of these timestamps.

NTP packets:

Frame 779: 90 bytes on wire (720 bits), 90 bytes captured (720 bits) on
interface 0
    Interface id: 0 (en1)
    Encapsulation type: Ethernet (1)
    Arrival Time: Jan 14, 2017 10:22:46.628995000 PST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1484418166.628995000 seconds
    [Time delta from previous captured frame: 0.279231000 seconds]
    [Time delta from previous displayed frame: 0.279231000 seconds]
    [Time since reference or first frame: 129.296382000 seconds]
    Frame Number: 779
    Frame Length: 90 bytes (720 bits)
    Capture Length: 90 bytes (720 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:ntp]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: Apple_a2:57:7b (a8:8e:24:a2:57:7b), Dst:
Actionte_1a:57:9e (00:26:b8:1a:57:9e)
Internet Protocol Version 4, Src: 192.168.1.10, Dst: 17.253.26.253
User Datagram Protocol, Src Port: 123, Dst Port: 123
Network Time Protocol (NTP Version 4, client)
    Flags: 0x23, Leap Indicator: no warning, Version number: NTP Version 4,
Mode: client
    Peer Clock Stratum: secondary reference (2)
    Peer Polling Interval: 6 (64 sec)
    Peer Clock Precision: 0.000001 sec
    Root Delay:    0.0334 sec
    Root Dispersion:    0.0335 sec
    Reference ID: 17.253.26.253
    Reference Timestamp: Jan 14, 2017 18:20:38.646497000 UTC
    Origin Timestamp: Jan  1, 1970 00:00:00.000000000 UTC
    Receive Timestamp: Jan  1, 1970 00:00:00.000000000 UTC
    Transmit Timestamp: Jan 14, 2017 18:22:46.628854000 UTC

Frame 780: 90 bytes on wire (720 bits), 90 bytes captured (720 bits) on
interface 0
    Interface id: 0 (en1)
    Encapsulation type: Ethernet (1)
    Arrival Time: Jan 14, 2017 10:22:46.663003000 PST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1484418166.663003000 seconds
    [Time delta from previous captured frame: 0.034008000 seconds]
    [Time delta from previous displayed frame: 0.034008000 seconds]
    [Time since reference or first frame: 129.330390000 seconds]
    Frame Number: 780
    Frame Length: 90 bytes (720 bits)
    Capture Length: 90 bytes (720 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:ntp]
    [Coloring Rule Name: UDP]
    [Coloring Rule String: udp]
Ethernet II, Src: Actionte_1a:57:9e (00:26:b8:1a:57:9e), Dst:
Apple_a2:57:7b (a8:8e:24:a2:57:7b)
Internet Protocol Version 4, Src: 17.253.26.253, Dst: 192.168.1.10
User Datagram Protocol, Src Port: 123, Dst Port: 123
Network Time Protocol (NTP Version 4, server)
    Flags: 0x24, Leap Indicator: no warning, Version number: NTP Version 4,
Mode: server
    Peer Clock Stratum: primary reference (1)
    Peer Polling Interval: 6 (64 sec)
    Peer Clock Precision: 0.000002 sec
    Root Delay:    0.0000 sec
    Root Dispersion:    0.0011 sec
    Reference ID: Unidentified reference source 'GPSs'
    Reference Timestamp: Jan 14, 2017 18:22:40.409336000 UTC
    Origin Timestamp: Jan 14, 2017 18:22:46.628854000 UTC
    Receive Timestamp: Jan 14, 2017 18:22:46.637396000 UTC
    Transmit Timestamp: Jan 14, 2017 18:22:46.637419000 UTC


On Sat, Jan 14, 2017 at 10:55 AM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> The issue with using Wireshark is that it still is looking at a ping. It
> may tag the
> event to one more digit, but all of the earlier mentioned issues with
> pings are
> still there. Simply put, they aren’t the greatest thing for testing timing.
>
> Bob
>
>



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