Can arp requests cause latency issues?

mohtasham1983 · 10-14-2009, 04:24 PM

Hi,

Recently, I started using comcast as my internet provider. I haven't bought a router, yet. I am connecting my laptop to their modem through cable. The bandwidth is pretty good, but I'm having issues with long latency.

The other day I noticed that there's a lot of network activity on my computer, even though I wasn't using any internet based application. After capturing packets using wireshark, I saw a lot of arp requests from different computer entering my computer.

I was wondering if anyone knows whether or not my long latency issue is related to receiving broadcasted arp requests?

Thanks in advance.

cyent · 10-14-2009, 05:03 PM

Quote:

Originally Posted by mohtasham1983

Hi,

The other day I noticed that there's a lot of network activity on my computer, even though I wasn't using any internet based application. After capturing packets using wireshark, I saw a lot of arp requests from different computer entering my computer.

I was wondering if anyone knows whether or not my long latency issue is related to receiving broadcasted arp requests?

Probably not. To confirm post some of the wireshark traces please.

More likely to cause delays are DNS lookups.

mohtasham1983 · 10-14-2009, 07:31 PM

Here is some of wireshark traces"

Code:

"No.","Time","Source","Destination","Protocol","Info"
"1","0.000000","Cadant_24:32:c1","Broadcast","ARP","Who has 98.234.86.111?  Tell 98.234.84.1"
"2","0.008730","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.20.0?  Tell 69.181.16.1"
"3","0.055640","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.23.30?  Tell 69.181.16.1"
"4","0.122119","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.68?  Tell 73.68.172.1"
"5","0.192828","Cadant_24:32:c1","Broadcast","ARP","Who has 98.207.96.68?  Tell 98.207.96.1"
"6","0.230476","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.16.74?  Tell 69.181.16.1"
"7","0.264535","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.22.33?  Tell 69.181.16.1"
"8","0.414039","Cadant_24:32:c1","Broadcast","ARP","Who has 98.234.84.89?  Tell 98.234.84.1"
"9","0.427494","Cadant_24:32:c1","Broadcast","ARP","Who has 98.207.97.90?  Tell 98.207.96.1"
"10","0.440745","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.69?  Tell 73.68.172.1"
"11","0.478161","Cadant_24:32:c1","Broadcast","ARP","Who has 98.234.86.92?  Tell 98.234.84.1"
"12","0.547772","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.20.208?  Tell 69.181.16.1"
"13","0.615181","Cadant_24:32:c1","Broadcast","ARP","Who has 98.234.86.99?  Tell 98.234.84.1"
"14","0.651815","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.59?  Tell 73.68.172.1"
"15","0.652028","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.58?  Tell 73.68.172.1"
"16","0.695372","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.60?  Tell 73.68.172.1"
"17","0.782318","Cadant_24:32:c1","Broadcast","ARP","Who has 98.207.97.213?  Tell 98.207.96.1"
"18","0.940533","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.70?  Tell 73.68.172.1"
"19","1.025575","Cadant_24:32:c1","Broadcast","ARP","Who has 69.181.20.151?  Tell 69.181.16.1"
"20","1.035555","Cadant_24:32:c1","Broadcast","ARP","Who has 73.68.172.71?  Tell 73.68.172.1"

Note that when you go on detail, source IP address is different in every packet. Its IP address is similar to the one that's asking to be told to.

Yes, there's a huge delay on DNS lookups. When I go to gmail.com, it takes forever to look up gmail, and then it takes another time to find mail.google.com to redirect me to it.

Edit: I think it's normal for a computer to receive so many ARP requests if it's directly connected to the cable modem. I also think getting a router will decrease the DNS lookup time, as most likely it will contain a DNS server. I'm not sure about this one till I test it.

cyent · 10-14-2009, 08:18 PM

Quote:

Originally Posted by mohtasham1983

Here is some of wireshark traces"

Note that when you go on detail, source IP address is different in every packet. Its IP address is similar to the one that's asking to be told to.

I suspect something upstream of you is misconfigured... but that isn't your problem. It's just eating a small bit of your bandwidth.

Quote:

Yes, there's a huge delay on DNS lookups. When I go to gmail.com, it takes forever to look up gmail, and then it takes another time to find mail.google.com to redirect me to it.

Yip, that'll be your problem then. Especially if you are using firefox, (the DNS lookup is in the same thread as the UI, causing the UI to lockup in a bloody frustrating manner until the DNS lookup completes.)

Quote:

I also think getting a router will decrease the DNS lookup time, as most likely it will contain a DNS server. I'm not sure about this one till I test it.

I doubt if that will help.

What I find does help is the firefox addon adblock plus.

I find that 90% of the slow DNS lookups are ad servers. Soon as I see firefox freezing up I open up adblocks blocking list and block likely looking ad urls. Bang. Problem goes away forever.