Networking

Front 1

True or False? Explain why: Modern networks are so reliable we don't need to worry about lost packets.

Back 1

FALSE.
Packets travel around networks. Packets contain some amount of information. However, a packet doesn’t know how to get to its destination. Even the source host doesn’t generally know a route to the destination (only if the destination is on the local network). A packet is like a postcard with the address written on it: it relies on the routers it passes though to make the right decisions.

To maintain maximum Interoperability, the Internet is built heavily on the TCP/IP stack. TCP/IP is a complete suite of networking protocols. The Internet Protocol (IP) is one of the protocols in the TCP/IP stack and is used for the communication of datagrams over a network. IP is an unreliable protocol. This is a technical term that means that it does not guarantee delivery of packets.

Although it is not necessary to use IP on a network, many modern networks are integrated into the Internet and so most know how to deal with IP. This means that modern networks should be concerned about how to deal with lost packets, because they need to know how to deal with the unreliable nature of IP.

Front 2

True or False? Explain why: NAT is enough to solve IPv4 address exhaustion problem.

Back 2

FALSE.

NAT = Network Address Translation.

NAT is a method of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device.

An IP address needs to be unique to every device that connects to a network, and consists of four groups of up to three numbers - 192.168.111.123 is an example. However, this means that there's a limit to the amount of addresses available, and a lot are specially reserved for certain purposes. There are simply not enough IPv4 addresses for the amount of devices currently used.

Using NAT means that lots of network connected devices can be "masked" under one single IP address, largely reducing the number of IP addresses required for each individual device. It does create the problem the the "outside world" cannot see any individual device addresses other than the routers IP. Multiple devices look like they have the same IP address.

NAT hasn't solved the IPv4 address exhaustion problem, it's merely postponed the inevitable death of IPv4 (old habits die hard). Devices connected to the Internet are still increasing, so even with NAT, there is still a problem. The solution to the exhaustion problem is IPv6.

IPv6 uses increased size address spaces, massively increasing the number of addresses available for devices to use. The number is so huge it should be okay for the future.

Front 3

True or False? Explain why: In IPv6 MTUs are big enough so that there is not a fragmentation problem.

Back 3

TO BE FILLED IN

Front 4

True or False? Explain why: There is so many computers on the Internet a hacker won't be able to find my computer and so I don't need a firewall.

Back 4

FALSE.

The Internet is open and vulnerable so being connected to Internet means you are at risk of a whole array of cyber threats. Hackers are just one of the many threats that firewalls help prevent. It could be the case that you never get hacked, but you could accidentally download some malware and you have no firewall to prevent the download from happening.

A firewall works as a barrier, or a shield, between your PC and cyber space. When you are connected to the Internet, you are constantly sending and receiving information in small units called packets. The firewall filters these packets to see if they meet certain criteria set by a series of rules, and thereafter blocks or allows the data. This way, hackers cannot get inside and steal information such as bank account numbers and passwords from you.

Front 5

True or False? Explain why: Nobody uses the ISO 7 layer model as it's slower than the 4 layer model.

Back 5

TO BE FILLED IN

Front 6

What is fragmentation in the IP? [2 marks]

Back 6

IP fragmentation is an Internet Protocol (IP) process that breaks datagrams into smaller pieces (fragments), so that packets may be formed that can pass through a link with a smaller maximum transmission unit (MTU) than the original datagram size. The fragments are reassembled by the receiving host

Front 7

What are the fragmentation fields in IPv4 headers and how does it solve the fragmentation problem?

Back 7

A three-bit field, used to control or identify fragments. They are (in order, from high order to low order):- bit 0: Reserved; must be zero.[note 1]- bit 1: Don't Fragment (DF)- bit 2: More Fragments (MF)If the DF flag is set, and fragmentation is required to route the packet, then the packet is dropped. This can be used when sending packets to a host that does not have sufficient resources to handle fragmentation. It can also be used for Path MTU Discovery, either automatically by the host IP software, or manually using diagnostic tools such as ping or traceroute. For unfragmented packets, the MF flag is cleared. For fragmented packets, all fragments except the last have the MF flag set. The last fragment has a non-zero Fragment Offset field, differentiating it from an unfragmented packet.