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I regularly use a VPN connection to connect to a PC located at my employer's office. Most of the time this works fine, with ping times of ~30ms it feels just like being in the office. However, from time to time I notice that the ping times are much longer.

When this happens I do a tracert to see if I can narrow down the cause of the delay. Today, this is occuring between the following 2 routers:

Tracing route to ....com [x.x.x.x]
over a maximum of 30 hops:

  1     *        *        *     Request timed out.
  2     *        *        *     Request timed out.
  3     *        *        *     Request timed out.
  4    31 ms    77 ms    20 ms  Xe5-0-4-0-grtontl3.red.telefonica-wholesale.net
[213.140.51.181]
  5    20 ms    20 ms    20 ms  Xe4-2-0-0-grtlontc1.red.telefonica-wholesale.net
 [84.16.15.237]
  6    84 ms    80 ms     *     ge-6-1-1.BR2.LND9.alter.net [146.188.112.93]
  7    84 ms    82 ms    82 ms  so-2-2-0.XT2.LND9.ALTER.NET [146.188.7.245]
  8     *       81 ms     *     POS0-0.GW10.LND10.ALTER.NET [158.43.150.126]

Is there any way I can reconfigure my home PC to use a different route, or should this be something that should be escalated to alter.net for investigation ?

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Are there any other people/computers on your home network? If they are using heavy internet traffic this could cause a higher ping. Check they aren't using P2P software such as uTorrent or see if your computer is downloading updates. Also, what is the OS and VPN client/server? –  tombull89 Sep 6 '11 at 14:23
    
Tom - I'm using 2 machines, one XP and one Vista. I'm sure that any other computers on my home network are not accessing anything (certainly no P2P). Perhaps it's my lack of understanding, but given that the ping times to the first node (213.140.51.181) were mostly around 20ms doesn't this mean the problem must be elsewhere ? –  stevec Sep 7 '11 at 11:17

1 Answer 1

I would first try WinMTR and let it run for about an hour. If latency never gets above 100 ms, you probably will have little recourse. ISPs will typically guarantee less than 100 ms to the first hop, and you'll be hard pressed to have them guarantee less than that or anything at all to a hop they don't control. The only point of contact you'll have is your ISP, they will have to do the rest if they do not control the network or have agreements with the peers along the way. Most likely if there is a proven issue they will just simply change your route. You'll be hard pressed to have them change your route just for slightly higher ping times a portion of the time - ISPs typically only make these sorts of changes for drastic issues.

You are correct in that it seems when it hits Alter.net's routers that the ping time increases, but this doesn't necessarily mean that other traffic is receiving the same latency (ICMP is almost always given the lowest priority). Keep in mind that if alter.net is the ISP for your office connection, you'll want to call them directly. You will need different data for this side of things. Again, as an ISP, they'll guarantee 100 ms or less to the first hop. Ping from the office to their primary dns for about an hour. If it doesn't go above 100 ms, they probably won't do anything about it. I would ask at the very least to see if there is a better trunk they could put you on. ISPs will do this, but it requires some pushing from the customer.

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"guarantee ... anything at all to a hop they don't control" - that's what I suspected. As an ISP I clearly wouldn't want to be liable for other infrastructure on the internet. I guess I was hoping for a way I could re-configure my PC change the route that the packets take across the internet. (alter.net isn't my employers ISP - today a tracert shows a completely different route that avoids those nodes entirely.) –  stevec Sep 7 '11 at 11:19
    
If your route changes constantly, it might be based off of some sort of least-cost routing policy. Basically, packets get sent a direction that will cost the ISP the least amount of money, and if that changes, your route changes. It is annoying, but there isn't anything you can do about it. –  MaQleod Sep 7 '11 at 14:53

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