Max ping response time?

ping response-time

28,203

Solution 1

I'm wondering what a maximum (practical) ping response time might be. As far as I know, there isn't a max defined anywhere (TTL, but that's hops, not time).

Theoretically, the time between echo request and reply can be long. From a quick glance at RFC 1122 I don't see any formal constraints here.

Practically though, there's a threshold value after which lack of reply will be treated as no reply at all (timeout). The specific value depends on implementation:

In Windows it's 4 seconds.
With iputils implementation of ping it seems to be 10 seconds - not sure about it, as it's not stated in the man page, but the code says something like this:
```
 #define MAXWAIT         10              /* max seconds to wait for response */
```

Ping responses longer than that are equivalent to no responses at all. So, I think it's safe to assume this to be the practical limit.

One thing to note - I'm talking here about ICMP only. If you meant some other "ping" (for example delay between some application-specific request/response), it will probably differ completely.

Solution 2

It's worth noting that an implementation of RFC1149 achieved this ping time:

64 bytes from 10.0.3.1: icmp_seq=0 ttl=255 time=6165731.1 ms

...which is about 102 minutes. I've yet to see a longer response time.

28,203

DougN

Updated on September 17, 2022

Comments

DougN almost 2 years

I'm wondering what a maximum (practical) ping response time might be. As far as I know, there isn't a max defined anywhere (TTL, but that's hops, not time). As I think about it, I'm not sure I've ever seen a ping response time of more than a second or so. But as far as I know, there is nothing to stop a remote host from waiting (or being really busy) and not sending the response back for a few seconds.

As a simple data point, I just pinged a number of servers around the world and the worst time I could find was 350ms.
- ThatGraemeGuy about 14 years
  
  If you could travel back in time and have the great privilege of working with some badly congested 64kbps WAN links you could see responses of 30000ms more often than you could ever want. ;-)
- YwH about 14 years
  
  @Graeme +1. I've seen responses like that too, but from broken packet shaper boxes that seemed to be queuing forever when things got congested. It was not uncommon for me to get ping responses as much as 10 minutes later. Yes, that is 600,000 ms. That sort of thing should be outlawed. And this was as recently as 2008.
- Berkay about 14 years
  
  @Graeme Donaldson, it's not possible, pls see me answer
- Chris J about 14 years
  
  For what purpose do you need to know this (i.e., are you looking at configuring something to raise alerts on extended ping times) - or is it just idle curiousity? :-) It will probably affect the answer(s) [i.e., theoretical as currently being discussed] or practical advice.
- Rob Moir about 14 years
  
  It's perfectly possible to see some very high ping times. Likely these days, with improvements to the quality of links and default timeouts set low to reflect that? Not so much.
- dbasnett about 14 years
  
  The more non-purposeful ICMP traffic generated, the closer to the day we get when the ISP's turn off ICMP entirely. See answer below.
- Vi. about 14 years
  
  I have usual ping time around 300 ms. en.wikipedia.org/wiki/Telecommunications_in_Belarus
DougN about 14 years

That's funny, but I guess I should have specified ping times for an electronic network, not one built from carrier pigeons :)