What is acceptable delay?

[enikk]

I have a 3 2611 Routers in a hub and spoke VPN configuration tunneling over DSL lines utilizing GRE and DES encryption. The hub router is in Michigan and the 2 spoke routers are in Vancouver and Edmonton. When i do ping tests my average delay time is between 100 and 120 ms through the tunnel and 90 and 100 to the WAN IP. Packet loss is almost non-existant. All the traffic passing through is basically acsii text accessing an application running on a server in Michigan.

Is this an acceptable range for delay? Should i anticipate any problems down the road? What is considered "good" and what is considered "bad" when it comes to delay?

Thanks

Tony

IT Director

Hydra-flex

[thisisshanky]

What is the speed of the dsl links ? since its over the internet we cannot really say a fixed delay value.

[enikk]

The link speeds are 2 MB at the hub and 1.5MB at the spokes, but does that really matter? I'm not concerned whether i'm getting good speeds in comaprison to my DSL speeds. I'm concerned with what is accepatable delay for the communication of data.

Tony

[thisisshanky]

Data usually is not delay sensitive, unless u have applications running over protocols such as SNA or you are running Voice over IP, which has a one way delay requirement of 150 ms. Tunnel and IPSEC introduce extra over head and delay in placing the packet on to the dsl line. This can be counted on as serialisation + processing delays. Though these kinds of delays are kinda fixed, the time the packet takes to reach from source to destination is variable. Since your communication is going over the internet, it all depends on your the upstream service providers between the two sites.

[enikk]

So if i am running an application on a unix box that utilizes telnet connections from my spoke locations and i am receiving 120 ms delays, that is not going to be a performance hit than?

I configured everything from the hub location so it is hard for me to tell(other than asking people there) if the delay is affecting performace or adding lag.

I guess aslo what i am asking is...Considering the delay and use, would a VPN configuration be an acceptable solution in this situation in the IT world?

Thanks,

Tony

[thisisshanky]

I would say for your normal data apps like telnet and other stuff, including web surfing, acceptable delay times can go to a max of 250 ms. This value is not one that i suggest, but i remember reading about this some time back.

You might want to monitor the BWs usage of your links, to find whether SLAs are met with your ISP. You might also want to ask users at remotes, if they are experiencing any delays while using apps.

Considering the amount of security that you need for protecting confidential data, i think some level of delay should be acceptable.

You can check your DSL bw, using the following tool.

http://www.pcpitstop.com/internet/bandwidth.asp?print=1

Hope that helps!