VoIP - Location & latency



  • Since the board seems to be on a VoIP trend lately, (which I 100% approve of 🙂 ) I'd like to get some discussion regarding hosted servers, physical location, and latency.

    Let's assume you are using a VPS server.

    1. Latency & physical location -
      What is considered to be an acceptable latency from your office, to the hosted VPS? 40 ms works, but 20 ms is better. How much of a difference does that 20 ms make in regards to call quality?

    2. Physical location -
      This goes hand in hand with the entire latency chain, (Office, to PBX, to SIP provider to PSTN) It goes without saying, that the closer the PBX is to you, the better it is due to latency. Also, the closer the SIP provider is to your PBX, the better, for the same reason. I'd like to see some real world examples of what other IP pros are doing/seeing in this area. For example: Where is your office located, where is your VPS located, what is the latency in-between. Same goes for your PBX to SIP provider. Where is the SIP provider physically, and what is the latency in-between? Perhaps we could start a list where everyone could add to?

    EDIT:

    1. Hardware - Memory and storage-
      I typically like to see 2 GB of RAM on a FreePBX box for example. What about storage? Does a VPS with an HDD have a greater chance of call quality issues VS a VPS with SSDs

  • Service Provider

    Latency: 200ms is the line. Pretty much anything under 200ms you can't hear. Of course you don't want to go for 190ms and then get hit with spikes or find that you have sensitive users. You want the best latency that you can get within reason. But we don't worry about 20-40ms at all. That's so fast that no one cases.

    You only care about staying below 200ms and you only care about total time, not just one component of the path. It's end to end that matters. So if moving the VPS causes more delay between extensions but less delay to the trunk it might be break even. You have to look at the whole thing.


  • Service Provider

    @fuznutz04 said in VoIP - Location & latency:

    1. Hardware - Memory and storage-
      I typically like to see 2 GB of RAM on a FreePBX box for example. What about storage? Does a VPS with an HDD have a greater chance of call quality issues VS a VPS with SSDs

    SSDs serve no purpose unless you are dealing with some insane load of voicemails. Calls do not go through the disk in any way so the disk is not important.

    2GB of RAM is excessive unless you have tons of callers or are running lots of extra stuff. We normally use 512MB - 1024MB and have systems that have run for a long time on 256MB without issue. 2GB is just wasteful.



  • @scottalanmiller said in VoIP - Location & latency:

    Latency: 200ms is the line. Pretty much anything under 200ms you can't hear. Of course you don't want to go for 190ms and then get hit with spikes or find that you have sensitive users. You want the best latency that you can get within reason. But we don't worry about 20-40ms at all. That's so fast that no one cases.

    You only care about staying below 200ms and you only care about total time, not just one component of the path. It's end to end that matters. So if moving the VPS causes more delay between extensions but less delay to the trunk it might be break even. You have to look at the whole thing.

    In 1 example, I have a total of about 75 MS from office to PBX to trunk.


  • Service Provider

    @fuznutz04 said in VoIP - Location & latency:

    @scottalanmiller said in VoIP - Location & latency:

    Latency: 200ms is the line. Pretty much anything under 200ms you can't hear. Of course you don't want to go for 190ms and then get hit with spikes or find that you have sensitive users. You want the best latency that you can get within reason. But we don't worry about 20-40ms at all. That's so fast that no one cases.

    You only care about staying below 200ms and you only care about total time, not just one component of the path. It's end to end that matters. So if moving the VPS causes more delay between extensions but less delay to the trunk it might be break even. You have to look at the whole thing.

    In 1 example, I have a total of about 75 MS from office to PBX to trunk.

    Then you might be getting lean. Remember that YOUR latency is just half of it. You get 200ms between you and the other end point. If they use 100ms and you use 100ms you just squeak by. So if you have 75ms in one spot and 40ms in another then that is 115ms of your total envelope used up before the PSTN delay is introduced or the latency on their side. So that is pretty high.


  • Service Provider

    @fuznutz04 said in VoIP - Location & latency:

    1. Physical location -
      This goes hand in hand with the entire latency chain, (Office, to PBX, to SIP provider to PSTN) It goes without saying, that the closer the PBX is to you, the better it is due to latency. Also, the closer the SIP provider is to your PBX, the better, for the same reason. I'd like to see some real world examples of what other IP pros are doing/seeing in this area. For example: Where is your office located, where is your VPS located, what is the latency in-between. Same goes for your PBX to SIP provider. Where is the SIP provider physically, and what is the latency in-between? Perhaps we could start a list where everyone could add to?
      SSDs

    Our office is global. But most of the people are in the North East US. Our PSTN landing point in NYC and our PBX is located in NYC. So the latency between PBX and Trunk is minimal.



  • @scottalanmiller said in VoIP - Location & latency:

    @fuznutz04 said in VoIP - Location & latency:

    1. Hardware - Memory and storage-
      I typically like to see 2 GB of RAM on a FreePBX box for example. What about storage? Does a VPS with an HDD have a greater chance of call quality issues VS a VPS with SSDs

    SSDs serve no purpose unless you are dealing with some insane load of voicemails. Calls do not go through the disk in any way so the disk is not important.

    2GB of RAM is excessive unless you have tons of callers or are running lots of extra stuff. We normally use 512MB - 1024MB and have systems that have run for a long time on 256MB without issue. 2GB is just wasteful.

    That's my experience as well with HDDs. I've always ran my PBX on HDDs and haven't had any issues. Some VPS providers that offer "VoIP" servers, have both HDD options as well as SSD options. Is this purely a marketing thing to get more money? Like you said, unless the disk is being pounded by call recordings or voicemails, most people wouldn't even notice anything.

    With the latest distro of FreePBX, they are adding new things all the time that we don't use, but eat up memory. When we were running with 1 GB, we were approaching the limit and swapping to disk. We've since disabled many un-used modules, but still use a bit of memory. For example, i just spun up a fresh FreePBX box, and without doing anything else besides update, it is already using 366 MB of RAM.


  • Service Provider

    @fuznutz04 said in VoIP - Location & latency:

    @scottalanmiller said in VoIP - Location & latency:

    @fuznutz04 said in VoIP - Location & latency:

    1. Hardware - Memory and storage-
      I typically like to see 2 GB of RAM on a FreePBX box for example. What about storage? Does a VPS with an HDD have a greater chance of call quality issues VS a VPS with SSDs

    SSDs serve no purpose unless you are dealing with some insane load of voicemails. Calls do not go through the disk in any way so the disk is not important.

    2GB of RAM is excessive unless you have tons of callers or are running lots of extra stuff. We normally use 512MB - 1024MB and have systems that have run for a long time on 256MB without issue. 2GB is just wasteful.

    That's my experience as well with HDDs. I've always ran my PBX on HDDs and haven't had any issues. Some VPS providers that offer "VoIP" servers, have both HDD options as well as SSD options. Is this purely a marketing thing to get more money? Like you said, unless the disk is being pounded by call recordings or voicemails, most people wouldn't even notice anything.

    With the latest distro of FreePBX, they are adding new things all the time that we don't use, but eat up memory. When we were running with 1 GB, we were approaching the limit and swapping to disk. We've since disabled many un-used modules, but still use a bit of memory. For example, i just spun up a fresh FreePBX box, and without doing anything else besides update, it is already using 366 MB of RAM.

    What is the output of free -m ?



  • @scottalanmiller said in VoIP - Location & latency:

    @fuznutz04 said in VoIP - Location & latency:

    @scottalanmiller said in VoIP - Location & latency:

    @fuznutz04 said in VoIP - Location & latency:

    1. Hardware - Memory and storage-
      I typically like to see 2 GB of RAM on a FreePBX box for example. What about storage? Does a VPS with an HDD have a greater chance of call quality issues VS a VPS with SSDs

    SSDs serve no purpose unless you are dealing with some insane load of voicemails. Calls do not go through the disk in any way so the disk is not important.

    2GB of RAM is excessive unless you have tons of callers or are running lots of extra stuff. We normally use 512MB - 1024MB and have systems that have run for a long time on 256MB without issue. 2GB is just wasteful.

    That's my experience as well with HDDs. I've always ran my PBX on HDDs and haven't had any issues. Some VPS providers that offer "VoIP" servers, have both HDD options as well as SSD options. Is this purely a marketing thing to get more money? Like you said, unless the disk is being pounded by call recordings or voicemails, most people wouldn't even notice anything.

    With the latest distro of FreePBX, they are adding new things all the time that we don't use, but eat up memory. When we were running with 1 GB, we were approaching the limit and swapping to disk. We've since disabled many un-used modules, but still use a bit of memory. For example, i just spun up a fresh FreePBX box, and without doing anything else besides update, it is already using 366 MB of RAM.

    What is the output of free -m ?

    total used free shared buffers cached
    Mem: 1877 572 1305 0 52 153
    -/+ buffers/cache: 366 1510
    Swap: 2047 0 2047


  • Service Provider

    I'm very surprised that it is using that much. It's not a terrible amount, calls use essentially nothing. but it is a bit high.


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