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31

Most likely if they're a big university they are their own ISP, using BGP to connect their network to the internet via a number of upstream networks. Nothing stops them from using IP addresses they should not be using, and it would work in their local network. However, it won't work on the Internet. Their upstream networks providing them connectivity should ...


26

Even when sending packets across continents, a TTL of 255 is more than enough - there simply aren't more routers involved. Running a quick test (from Germany) shows 17 hops to the US and 18 to Japan. Usually, you don't get above 30 or so. This is due to the hierarchical structure of the Internet - you hit your ISP's backbone with just 2-5 hops, another 2-3 ...


26

Connecting an interface to a network makes it a part of that network. Therefore, the IP address is a property of the connection, not the host. Likewise, a host can have many network connections and accordingly, IP addresses. Different interfaces often have different functions, so it's important to distinguish between them (e.g. internal console, public ...


21

One of my buddies is saying that TCP will be a problem for this gateway because it is going to establish a new connection for every message it sends (not kafka but the underlying transportation protocol itself is the issue), requiring a new port each time. At the rate we'll be sending these clients messages (gigabytes), kafka will run out of ports to read ...


20

Only one device is allowed to transmit at any given time. At any other given time, another device is allowed to transmit. How can you have a conversation at a dinner table if only person can speak at any time?


19

The IPv6 documentation prefix (2001:db8:::/32) must be used ONLY for documentation purposes. It means written examples, diagrams, PPT presentations, Textbook explanations, etc. This range shouldn't be used in practical networks. There is a "private IP range" of fc00::/7 which should be used for device testing, demos, courses, etc. as per RFC4193 Unicast ...


19

You cannot multicast on the public Internet, but you can multicast across the public Internet to another site by using a tunnel that supports multicast. Multicast routing is very different from unicast routing, and all the routers in the path of the multicast packets need to have multicast routing configured.


19

Google in particular uses distributed datacenters around the globe. They announce the same IP network at various places and due to the way routing protocols work, you reach the nearest one. bbc.co.uk points to an IP address that belongs to Fastly, Inc, a content delivery network, that also has points of presence around the world, including Asia, but I don't ...


18

Some LAN protocols, on some media, are half duplex. That means that only one host on a LAN can send a frame at any given time. The classic example of this is the original ethernet, but the modern example is Wi-Fi. The original ethernet ran on coax, and it used CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to detect collisions where two ...


15

Because 224.0.0.0/24 is the range assigned by IANA for local multicast - Local Network Control Block. Addresses in this range are non-routable, they can only exist on a link, and cannot be forwarded by a router. These protocols only require multicast to operate within a single link, often to provide dynamic neighbour discovery and flooding of protocol ...


14

No. That said, let's see a simplified example: I have a computer with three interfaces: eth0 (wired Ethernet), wlan0 (wifi), and vboxnet0 (virtualbox). One of the interfaces is connected to an internal network, one is connected to the internet, and the last one is connected to a network of virtual computers. Let's say I have just one address, 10.1.2.3, and ...


14

IPv4 address space is in short supply, so some people decide to use IP space ( allocated, but not advertised) that doesn't belong to them. The consequences are pretty well described in the article you quote.


13

The requirement exists to prevent collisions. This is a bit more important than most people recognize. Even if you have systems which currently don't communicate with other systems over the internet you still need your addresses to be globally unique. You may now or in the future need to add a host which can communicate both with your internal network and ...


13

Is this okay? Hardly ideal. I assume since you are using cheap, obsolete switches, that you're on a very limited budget. You'll have to weigh the factors below. Does a cascade of switches affect overall performance? The problem with cascading switches is that you are concentrating traffic on the links to upstream switches. For example, the last switch ...


12

What stops them from attributing their routers and hosts already in use IP addresses? Nothing. Over the years, I have seen both organizations of all sizes, both public and private, do this including a world wide recognized "brand" company. In fact, I have seen this more often in business settings than university settings (largely due to the fact that more ...


11

If your test environment is separated from your local network you hypothetically could use any IPv6 addresses which are not reserved for special uses. However, if you are looking for an equivalent of private IPv4 adresses you should take a look in RFC4193. There you can see that fc00::/7 is the suitable subnet for testing purposes. On the other hand you ...


10

YANG is the answer here. To quote from RFC8345, which defines YANG: This document defines an abstract (generic, or base) YANG data model for network/service topologies and inventories. The data model serves as a base model that is augmented with technology-specific details in other, more specific topology and inventory data models. Protocols ...


10

When companies merge or set up an extranet to communicate, it has proven difficult with IPv4 Private addressing because the companies often use the same or overlapping address space, and that requires the ugly hack of NAT to get around, and that can cause problems and break many protocols. This was identified as a problem when IPv6 ULA was being developed, ...


9

No, that's not correct. You don't need a router for two hosts to communicate using IP as long as they're in the same network.


9

As an end-user, you cannot multicast across the Internet, unless using a tunnel. As a larger organization, like a video provider or an ISP, it is certainly possible to forward multicast packets across their domain boundary (i.e. across an Internet). How ? Essentially, to forward multicast packets within your own domain (or Autonomous System, AS), you use ...


9

A small addition to the other answers to be more complete: although many routers seem to send out packets with a TTL of 255 (for the packets they produce themselves of course, not those they forward!), most operating systems send out packets with much lower initial TTL values: Windows uses 128 (since Windows NT 4), MacOS X and Linux both use 64 Some ...


9

For the most part, no. Hubs are also known as repeaters - meaning that they basically echo whatever is coming in to a given port out all other ports in the domain. The idea is (or, more properly, was) to replicate the behavior of a shared piece of coaxial cable, meaning that the individual hosts had to assure that only one member of the LAN was ...


9

Router describes the general technical function (layer-3 forwarding) or a hardware device intended for that purpose, while gateway describes the function for the local segment (providing connectivity to elsewhere). You could also state that "you set up a router as gateway". Another term is hop which describes the forwarding in between subnets. It's just a ...


9

What is IP squat space Space that someone uses to number their networks even though it is either allocated to someone else or may be allocated to someone else in the future. "squat space" is generally not routed on the public internet by the squatter. Doing so would be considered a hijack which is a much more serious matter. Instead it is generally used ...


8

Just from the RFC I can't see anything defining that documentation is strictly written text. Do you have any source for this interpretation? According to the IANA IPv6 Special-Purpose Address Registry, the 2001:db8::/32 Documentation address range cannot be used in source or destination addressing, is not forwardable (routable) nor globally reachable, and ...


8

My question is: is it such a big deal to put cabling into a closed rack? No. It can make working on the cabling more difficult and add time (i.e. labor costs) to the work, but I have seen this done well plenty of times. Of course, many organizations choose to use top of rack switches or extenders rather than cabling. Is it such a big deal to have a ...


8

I would imagine that with TCP A will resend the packages until it's gotten an acknowledgement for them all which would degrade A's performance because of having to resend packages all day long (need confirmation on that thought as well) but with UDP or other such protocols the question remains. TCP has "the sliding window mechanism that controls the ...


8

8 bit is more than enough. because of ISP peering you can reach destination by travelling through less than 5 or 6 ISPs, and because of backbone network architecture, the packet will transfer only through 3 or 4 router maximum in one ISP. if you increase the TTL, for un-routed destinations, the packet will be travelling in network until TTL become 0 - which ...


8

My understanding is that when you establish a TCP connection, that connection remains open until it is timed out by the application or forcibly closed by either the server or client. From the perspective of TCP, there is no client or server (client/server is an application concept that is off-topic here). TCP establishes a connection between peers, and ...


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