Forum Discussion

Cblucas3's avatar
Cblucas3
Freshman
6 years ago

Latency Or Satellite Shortcomings?

There is all this talk of distance affecting latency which doesn't seem to wash. If the signal has to travel 88,000 miles latency shouldn't be an issue when the speed of light is considered. Traveling at 186,000 miles per second translates to 1,116,0000 miles per HOUR . In less than 1 second a packet of data will travel to the gateway and back 2 twice with time to spare.
So why am I having such poor latency? Can it be the Hughsnet hardware? I know the satellite can only handle a certain amount of client connections, requests and transmissions. If to many client requests are active they're then refused and the client modem has to resend the packet resulting in latency. Either that or the satellite holds those requests in a buffer which causes increased latency.
My question arose from the fact that my latency great improves at night. Usually 3 am to about 6 am. I assume that there is much less traffic at that time so the satellite immediately processes the packet instead of a refusal or buffering action.
If this is not the case than please tell me what reason there is for horrible latency other than distance.
Performance
  • GabeU's avatar
    GabeU
    Distinguished Professor IV
    6 years ago
    Cblucas3 wrote:
    There is all this talk of distance affecting latency which doesn't seem to wash. If the signal has to travel 88,000 miles latency shouldn't be an issue when the speed of light is considered.  

    It's actually higher than that, because you aren't on an island on the equator, directly "under" the satellite.  It's more like the mid 90s or so.  The latency due soley to distance will be at least somewhere around 500ms, and the further your location and your gateway's location from the satellite, the higher it will be.   Add the infrastructure the signal has to travel through and that adds another 100ms or so.  

     

    As others have stated, testmy's latency calculations of very often off by quite a bit, and consistently.  As also stated, the best latency calculations you can get are by running traceroutes.  

     

    The ES19 satellite has a capacity of around 200 - 225Gbps.  HughesNet has approximately 1.4 million customers.  How many of those customers are connected to the ES19 sat is anyone's guess, but it's likely no more than half, as there are still numerous people connected to the ES17 and older satelites, though the older ones are dwindling.

  • maratsade's avatar
    maratsade
    Distinguished Professor IV
    6 years ago

    Latency is a measurement of time delay in any kind of system. In satellite communications, it’s the length of time that it takes a signal to travel from your home to the satellite in orbit above the Earth), and then down to a ground-based gateway which connects you to the internet. Each leg of that journey is about 22,300 miles, which sounds like a long way until you realize that our signal travels at the speed of light ( 186,282 miles per second). The whole round-trip is measured in milliseconds, often referred to as “ping.” The ping on satellite internet is usually around 638 ms, compared to ping of 30 ms or less on a typical cable network.

     

    Edit: You say your latency improves at night. How are you measuring it? The most accurate method for measuring latency is by pinging a server. If you're using anything else, you're getting inaccurate data. 

     

    • maratsade's avatar
      maratsade
      Distinguished Professor IV
      6 years ago

      Each time a data packet ‘hops’ (that is, is handled by a device along the path) several milliseconds of latency are added. The physics involved account for approximately 550 milliseconds of latency, a limitation shared by all satellite providers.

       

      In addition to transmission times, there are other factors that contribute to the total latency experienced by the end user, factors such as the network itself, IP/satellite translation overhead, speed of upstream connections, and traffic (congestion). 

       

      All of these variables combined contribute to  and account for the differences you see in latency measurements.

      • Cblucas3's avatar
        Cblucas3
        Freshman
        6 years ago
        I'm aware and have taken all this and more into consideration.