Wireshark-users: Re: [Wireshark-users] localhost versus url

From: Tony Anecito <adanecito@xxxxxxxxx>
Date: Thu, 10 Mar 2011 10:12:31 -0800 (PST)
Hi Jaap,

Many thanks that makes sense. I do have a router with a set of static ips 
provided by my isp and one of the ips is registered with godaddy and is tied to 
my own domain name and that was what I was using prior to using localhost. I did 
notice on wireshark when using my domain I would see what you described.

I wonder what layers of the OSI 7 layer model is bypassed? I would think the 
first three (1-3) would be bypassed?

Thanks,
-Tony



----- Original Message ----
From: Jaap Keuter <jaap.keuter@xxxxxxxxx>
To: Community support list for Wireshark <wireshark-users@xxxxxxxxxxxxx>
Sent: Thu, March 10, 2011 12:19:12 AM
Subject: Re: [Wireshark-users] localhost versus url

Hello Tony,

Assuming your domain name is resolved to your public IP address on the outside 
of the firewall/NAT, your assumption is right.

When entering localhost in the URL, that's resolved to 127.0.0.1, your local 
machines loopback interface. No Ethernet networking involved, so watching with 
Wireshark won't show this traffic at all (unless capturing the on the loopback 
interface on a !Windows machine).

When entering the FQDN in the URL, that's resolved to your outside address. 
Browser traffic flows to that address first, then comes back to access the 
Apache server. Now you'll see the traffic when you capture on the network 
interface, once going out and once coming in.

In the circumstance that there's no NAT involved (so your outside address is 
your interface address) you still end up with more delay that going through the 
loopback interface. The extra DNS interactions, and probably additional safety 
measures of your platform, take away a little time for every object retrieved.

Thanks,
Jaap

On 03/09/2011 11:11 PM, Tony Anecito wrote:
> Hi All,
> 
> I was running some performance tests last week and noticed with the client app
> running on the same server or apache web server machine the response time was
> much better when using localhost in the url versus my domain name. I assumed
> somehow the connection is bypassing my router and connecting to the apache
> process directly. Is that so and if not what should I see on Wireshark if
> anything? Or is even the tcp/ip stack short circuited?
> 
> Thanks,
> -Tony

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