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Is it common for ISPs to connect to each other directly?

Yes, this does happen quite a lot, and it is called private peering. It has some benefits over peering over an IXP: dedicated bandwidth, you can be sure you can use the full capacity of the ...
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14 votes
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How do routers on the backbone avoid IP address conflicts?

The RIRs assign addressing to the ISPs. An ISP not following the rules will quickly find itself ostracized and cut off from the rest of the Internet. IANA owns the addressing and assigns each of the ...
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12 votes
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Who pays for traffic when it transits multiple providers

EDIT: I forgot to mention this - if you're interested, there have been books written about this topic. I highly recommend Bill Norton's The Internet Peering Playbook. Available in print or digital ...
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10 votes
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Who assigns IP s to the ISP s?

IANA is responsible for the assignment of IP-blocks and AS-numbers to regional internet registries (RIRs). There are 5 RIR's: RIPE (Europe, Middle East, Central Asia) AfriNIC (Africa) APNIC (Asia-...
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10 votes

What's the difference between autonomous systems, ISPs and RIRs?

You are pretty accurate. IANA is the Internet Assigned Numbers Authority. Its function is to make sure that numbers that need to be unique are actually unique. That includes protocol values, IPv4 ...
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10 votes

What does "10Gbps wave connection" mean?

Most likely they mean a wavelength on a DWDM path. With DWDM, a fiber operator can use one single pair of fibers to carry a number of different colors (wavelengths) of light using multiplexing. Each ...
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8 votes
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Is the Slow-Start algorithm responsible for ISP speed throttling?

Short answer: No, ISPs do not use TCP Slow-Start as the main way to throttle customer bandwidth. Long answer: There are many ways that an ISP can throttle the bandwidth a particular customer gets ...
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8 votes
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Why is the internet *not free?

Most ISPs have to buy service from other ISPs to be able to reach every part of the internet. That is called "transit". If you start a small ISP you usually buy transit from one or more bigger ISPs. ...
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8 votes
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Single Public IP Address for multiple physical locations

Based on your edit, it sounds like you want anycast. This is a common among large, global companies. You advertise the same network from multiple places, and routing will take traffic to the closest (...
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8 votes

Is a point-to-point T1 line literally a line in real life?

No. There may be a dedicated circuit between the routers and the nearest telco central office, but between offices they are switched and multiplexed onto other, higher capacity circuits. Today, most ...
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8 votes

If IPv6 exists, why do we still pay for static IPv4 addresses?

IPv4 and IPv6 are two different protocols. They are not interchangeable without a lot of work. So if you want to talk to v4 devices you run v4. If you want to talk to v6 devices you run v6. Most of ...
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8 votes
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In practice, how are BGP Advertisement destinations determined and configured?

Some connection between the two ISPs is needed. Dedicated fibers (for example in a datacenter they're both present in) is very common. But there are other possibilities: a layer 2 connection (for ...
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7 votes
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Two ISP bgp topology?

Even if you could still get PI IPv4 addresses in Asia: if your ISPs don't want to route your IP addresses then there is nothing you can do. Tunnels and LISP could solve some of your problems (I use ...
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7 votes

Who pays for traffic when it transits multiple providers

Who pays for traffic when it transits multiple providers? Ultimately, you do. John Jensen did a fantastic job explaining how this works overall, but I suspect a diagram could help. I will borrow the ...
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7 votes
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Prefix hijacked by another ISP

At this moment, there's not that much that ISP's can do to prevent these kind of hijacks except, as you said, doing proper filtering of received and announced prefixes. Unfortunately many ISP's still ...
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7 votes
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BGP null route when DDoS?

The only answer we can give you is 'talk to your ISP'. Remotely triggered blackholing (RTBH) is an often used technique, but we can't tell if your ISP supports this. When using RTBH, you can announce ...
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7 votes

What are the significance of different types of routers?

These are not different types of routers, they are different roles. It usually depends on where, topologically, the device placed in the network. Edge routers, for example, are placed at the network ...
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7 votes

Is a point-to-point T1 line literally a line in real life?

Literally? No. Unless the devices were very close, it's very unlikely they would ever have been directly connected. Even 20-30 years ago, in the era of T1's, there were repeaters, digital cross-...
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6 votes

Why doesn't ISPs reset DSCP at the edge before delivering traffic to customers?

I have no practical experience in running CoS/DSCP in ISP networks, but a logical explanation would be that it doesn't make sense to just change fields in a header. Even if I as an intermediate ISP ...
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6 votes
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Multi-homing and BGP routing with less than /24

Most transit provider will refuse to announce tough BGP a prefix longer than /24. (I.E. /25 for example) It's related to the size of the routing tables in the routers. You have to understand that ...
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6 votes
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Can I set two gateways or more on the same subnet with NAT on a Cisco router?

I think you misunderstood how a router process a packet, thus coming with a solution that is not at all appropriate for your needs. Why? Let say computer A has the following configuration: mac ...
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6 votes

Can ISP know computer MAC address in local network?

A mac address doesn't make it past the first hop (most likely your home router). It stays local to the broadcast network. IMEI isn't transmitted over wifi, so your ISP will also not see your IMEI. ...
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6 votes
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How does a ping to a public IP work in my same AS?

In general, traffic to addresses within your network should never go via your upstream ISP. Routers in your network should have a route for the every IP prefix in your network and exchange those via ...
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6 votes

Is it common for ISPs to connect to each other directly?

My understanding is that IXPs provide the primary means of ISPs to connect with each other I think that is a massive oversimplification. In general connections between autonomous systems (this ...
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6 votes

Can I make 2 ISP providers' IP addresses into 1 IP address?

While it might not be possible to solve your narrow question about IP addresses without provider-independent addressing and control of your own routing, it is certainly possible to do something the ...
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6 votes
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What does NAT64 do which can't be done by deploying IPv6 + NAT444?

What it does is simplify your network administration, particularly for large high-traffic networks. Running dual stack means administering two seperate IP allocations for every network. Running IPv6 ...
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5 votes

Cisco / Spanning Tree on Access Ports from ISP

In my opinion, you've set things up "wrong". (and so has the ISP) Never, EVER, trust what the ISP puts on your link. If you're running a metro-e interface into a switch, everything possible should be ...
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5 votes
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Simple question: Cisco 1750 AUX Port as "ADSL WIC"

The first diagram will not work, and in fact may result in damage to your router. The AUX port is a regular RS232 serial port, which is completely incompatible with ADSL. Don't do it. The second ...
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5 votes
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Autonomous System Number overlap confusion

You need to think of the difference between IP Range "Announcement" vs Origin AS. So from the perspective of what Hurricane Electrics AS6939 sees announced from its Peers. If you look at the Whois ...
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5 votes

What causes packet loss when using full bandwidth from ISP?

There are a number of possibilities here, not limited to, but including: The CPE's CPU is maxing out. (CPE=Customer Premesis Device) Check the specifications for the router you are using to make ...
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