Physical internet ISP network question

[DarkoStoj]

Physical internet ISP network & fiber question

This was something I was just curious about. I am a little confused on how the actual physical network lines work.

So does a company have to dig up the roads to install line, then they own those lines or network grid or whatever you want to call it? If so, do they have a central location that manages all those networked lines or do they have multiple stations spread out all over by distance, amount of use, etc.

Say you have Comcast, AT&T, etc, do they share lines ever, or do they only use the physical lines they own and installed themselves? Is there such a thing as "common" or shared lines throughout a city?

So say I want to go to IP address 173.255.204.184. If they are on a Comcast network what is it that allows somebody from AT&T to access it?

If you are on fiber, how can you still download at fast speeds if something is hosted on a non-fiber line?

Dumb questions I know, but something I was always curious about.

 

[Tin]

The backbone of the internet is typically run underground or along the same poles as power lines in some instances, depends on the requirements of the deployment. Those usually go to switching stations, then to your home or office. The lines are shared at some point. If they weren't, then portions of the internet would be cut off.

 

[The Man]

your IP is owned by your current service provider. if you change providers, you get assigned an IP address on their network.

 

[RyeLou]

It sounds like you're asking a similar question to people who take a PC from 2000 and then shove a GTX 1080 in there and wonder why it runs like shit. Are you asking it like that? So, say you have an internet connection that's faster than www.somewebsite.com The expectation would be that you load only as fast as the slowest point between the two points, I'd assume.

 

[Killjoy]

Competitive ISPs don't share their cable infrastructure. If your neighborhood has Comcast, WOW and ATT, switching between ISPs requires the new provider to physically move (or replace) the cable drop to your house from one provider's cable infrastructure to the other (up on the pole). This is why it's difficult and expensive for a new ISP to enter a neighborhood - they'd need to run parallel cable infrastructure throughout, and secure whatever permitting for attaching to poles, using easements, etc.

For each local ISP, their customers on your block get aggregated at some point in subdivision, then multiple blocks aggregated in hubs, Hubs aggregated into headends, etc. All ISPs peer (connect) with others (but not all others) at predetermined physical points that are heavily negotiated/contracted with each other. If the two ISPs feel they are equals, and peering would be a mutual benefit, then they may peer for free. Otherwise, if the benefit is asymmetric, then the ISP gaining the extra benefit would be expected to pay to peer per whatever is negotiated. You also have typical politics in play where one ISP may not be willing to peer with another for whatever reason.

Not all ISPs are created equal, and a good analogy is the road system/hierarchy. Tier 1 ISPs are your Interstates (I-75, I-696, etc.). They carry a ton of traffic at very high speeds long distances (usually covering an entire country/continent/geography), but usually are not how people or businesses gain Internet access. Tier 1 ISP in the US would be ATT, Verizon, Sprint, L3/Global Crossing, Qwest, etc. A step down from there, Tier 2 ISP, like your regional M-roads, are large but only regional ISPs, like Cable & Wireless, Comcast, Telia, Hurricane Electric, Hibernia Networks. Tier 3 would be your small town/city ISPs, like the mile roads, and usually have to pay tier 1/2 ISPs for Internet access (peering).

If you have WOW, and your next door neighbor has Comcast, network traffic between you two would traverse out of the neighborhood, likely out of the city/county/region, to wherever the closest/best WOW-Comcast network peering point is. There maybe be one in the Detroit area, but more likely Chicago or NYC. And if WOW and Comcast don't have a peering agreement, then your traffic will route to yet another ISP who has a peering agreement with both and acts as the middleman. So, no, if you and your neighbor have different ISPs, traffic sent between you could easily route over hundreds of miles in one big loop.

Take all of of this with a grain of salt - short summary of a complex topic. This should give you the general idea though....

 

[wrath]

They share all over the place. Often many carriers share the same physical line but someone owns the dark fiber and splits off spectrum using DWDM. The "last mile" is usually owned by one company but there is often a peering agreement that makes it cost prohibitive for anyone else to sell it to you.

 

[LT1Pat]

I think it's easiest to oversimplify it and look at it like a big home network. Nobody owns the internet and exchanges between ISP's are handled through peering agreements. I think the peering agreement is the part you're interested in.

It goes Last Mile (your home, business, campus, etc) --> ISP (Comcast, AT&T, etc) --> Long distance backbone (Verizon, AT&T, Sprint). Backbone providers will sell to ISP's, and ISP's will sell connectivity to you.

I don't think Comcast owns much long distance backbone infrastructure. They likely purchase from the backbone providers. Comcast probably has a local hub in neighborhoods that services a few thousand customers but then uses a backbone provider for their long distance fiber.

Your traffic speed is only as fast as the bottleneck. If you're on 10Gb and the IP address you're talking to only has a 56k modem then you can only talk as fast as their 56k modem. By fast I mean bandwidth. Think of bandwidth like a water pipe where the diameter of the pipe is the bandwidth and the pressure is the ping.

This was something I was just curious about. I am a little confused on how the actual physical network lines work.

So does a company have to dig up the roads to install line, then they own those lines or network grid or whatever you want to call it? If so, do they have a central location that manages all those networked lines or do they have multiple stations spread out all over by distance, amount of use, etc.

Say you have Comcast, AT&T, etc, do they share lines ever, or do they only use the physical lines they own and installed themselves? Is there such a thing as "common" or shared lines throughout a city?

So say I want to go to IP address 173.255.204.184. If they are on a Comcast network what is it that allows somebody from AT&T to access it?

If you are on fiber, how can you still download at fast speeds if something is hosted on a non-fiber line?

Dumb questions I know, but something I was always curious about.

 

[little2v]

Comcast is actually a Tier 1 ISP. People pay them, they don't pay anyone anything. They actually own/operate one of the largest backbones. They were even the first to do 100 gig. They carry more traffic than anyone.

 

[WhiteHawk]

Porn. Lots of Porn.

 

[Killjoy]

Yea, it's a little convoluted nowadays. The different tier levels were more clear cut in '90s and '00s. This is why I said - take it with a grain of salt.

Comcast, to my understanding, is still buying transit from Tata and NTT, which by definition makes them a Tier 2. I have no way to validate the accuracy of this. My understanding is that this purchased transit is ~1% of Comcast's total peering volume, so very negligible. But yes, they like to act like a Tier 1 otherwise, and yes, they do operate a large network & backbone in NA.

However, if you want to talk large Tier 1 ISPs that have a broader reach than Comcast, both in the US and abroad, they'd have a hard time competing with L3, Cogent, Telia and other big boys. I'd even argue ATT is bigger. But, it's all penis measuring at the end of the day...

 

[Justindwright]

Comcast is actually a Tier 1 ISP. People pay them, they don't pay anyone anything. They actually own/operate one of the largest backbones. They were even the first to do 100 gig. They carry more traffic than anyone.

yup, they rent/lease their fibers to ATT, Verizon and a few others.