Re: How worried is too worried? Plus, a Global Crossing Story.

From: Steve Gibbard (no email)
Date: Fri Oct 26 2001 - 03:31:47 EDT

It sounds like time for an explanation of what Digital Island is. I'm
sure marketing will be upset with me for dropping the official "corporate
positioning" language, but here goes:

There are multiple pieces to Digital Island, the two biggest being an
Internet backbone network (mostly carrying web hosting traffic) and a
content delivery network (it competes with Akamai, which many of you are
probably more familiar with). I work in the hosting side of the company,
and have considerably less knowledge of the content delivery network, so I
won't promise to be entirely accurate here. The packets you're seeing
come from the content delivery network.

Content delivery networks consist of caching web servers spread out around
the world. When a user requests web content cached by the CDN, a DNS
request is sent looking up the caching server. The CDN then calculates
which caching server is closest to the requester (or more specifically,
the DNS server the requester is using), and sends back the IP address of
the closest caching server. The user's web browser then contacts the
local caching server, and does the download from there.

My knowledge of how exactly those measurements are done is a bit hazy, and
Jason is certainly a better person to answer that than I am. However, the
ICMP echo requests you're seeing are at least part of the process, and
aren't being done unless your users are requesting content from our CDN.
They aren't being done at random, and aren't being done as part of a
research project. They're just being done to send you or your users the
content you or they requested from the right caching server.

I hope this helps. I'm sure somebody who knows more about CDNs (ours or
others) will jump in and correct whatever I've gotten wrong.


On Thu, 25 Oct 2001, Christopher Wolff wrote:

> I truely enjoyed the wide range of reponses to my Digital Island post. Everything from DI is perfectly justified to 'tell DI to stick it' haha.
> I certainly do not run the largest ISP, nor the smallest, but my small company is managing customer connectivity on both coasts of the continental US. My customers know me as the one that cares about their network infrastructure and can answer most questions quickly. I enjoy offering personal service.
> I also take pride in managing my network well. I know, for the most part, what kinds of traffic are passing through my network. This helps me take a proactive stance to issues before they become my customers' business impediments.
> Therefore, I have to respectfully take exception to the opinion of "Welcome to the Internet, there's nothing you can do, just don't worry about 441 packets."
> I partner with companies that share my view of network management. Recently I had an issue with a customer that was claiming poor throughput. Global crossing did everything in their power to analyze their network, my network, and my customers server farm. Although this turned out to be a TCP/IP tuning issue on the particular host, Global Crossing did not charge me a premium for investigating this issue.
> Throughout this resolution, Global Crossing earned my respect and confidence that I am *partnered* with a vendor instead of just buying bandwidth from them.
> Just my $0.02,
> Christopher J. Wolff, VP, CTO
> Broadband Laboratories

Steve Gibbard

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