networks

13COMP

Raspberry Pi

LINUX OS

assessment

A good place to start: Y12 networking

What are all the things that happen whe you send information over the internet?

This is a shameless AI explanation, but good and succinct.

Class brainstorm/memory test - What has to happen for a cat picture to get uploaded to instagram?

How do we think about it? Introducing the OSI model!

The OSI model is one of the two main ways network communication is described. You will find heaps if you search for it. If you find a great resource, leave a link in classroom.

Mr Britton thinks this one from computerphile is good.

Another AI production, but it's 95% good.

Layers 5, 6, 7 - The software layers

These are the software layers. These layers are where software developers do their stuff. Usually these get lumped together. They all happen before any networking takes place.

(Geek humor: An error on layer 8 is a user error - Same as a PEBCAK error)

Layers 2, 3, 4 - Logical networking layers

This is where the interesting stuff happens. We will examine this by looking at how the data is encapsulated.

Layer 4 - Transport - Segments or Datagrams

Data sent from the application to the operating system to be sent over the network

Usually via TCP or UDP - Both of these remember which application the data was from by creating a port (an identifying number)

TCP header

TCP guarantees delivery of all the packets in order so it includes a sequence number and an acknowledgement, it has a checksum to detect corruption and ask for a re-send.

UDP header

UDP is designed for speed. The header is tiny, it includes a checksum to detect corruption but if the packet is bad it is just discarded.

Layer 3 - Network - Packets

The data is ready to send. It just needs to know where to go. This is where the IP address is added. Of course it will look different depending on whether you are using IPv4 or IPv6

IPv4 header:
Variable length, up to 60 bytes

IPv6 header:
Fixed length 40 bytes

Layer 2 - Datalink - Frames

Now your computer needs to send on the data, unfortunately your computer can only talk directly to machines on it's network. To do this it adds a header with the hardware (MAC) address of the next router*.

*The protocol for working out which router is next is the Border Gateway Protocol

Ethernet Frame

Wifi Frame link

Encapsulation overview...

Layer 1 - The physical layer

Now you're dealing with physics. Electricity, light, radio. This is the place where things actually move.

And a quiz on the OSI model

And next - ICMP

Internet Control Message Protocol

A very handy layer 3 protocol. It's the mechanism behind ping and tracert.

A good article that describes ICMP very well in points 1 & 2 then goes into lots of detail about how it can be misused.

Check your understanding

Addressing methods: Unicast, multicast, broadcast

Review of everything we've done with network layers.

Extra stuff...

Quick look at various protocols

If you didn't like the one above, try this

Another more in-depth description of DNS of DNS

DNS nuaghtyness

DCHP

HTTP & HTML

SSH

If you encounter the issue below like this one....

You can use this command below to fix it, it will add the keys for the linux distro.

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 49023CD01DE21A7B

(you may just need to change the key value to correspond with your error)

port forwarding

Use the internet look up security issues with port forwarding...

what is ICMP?

traceroute is used to display the physical routing path between 2 internet devices communicating with each other. It maps out the journey from one router to another - sometimes called a hop. Using traceroute to diagnose network problems can help administrators locate the source of a network delay.

ping is a simpler traceroute. It sends out pings -- also referred to as echo request message -- and the measures the amount of time it takes the message to reach its destination and return the source. These replies are called echo reply messages. Pings are useful for gathering latency information about a specific device. Unlike traceroute, ping does not provide a picture map of the routing layout.

Looking at specific protocols

Who manages the protocols?

The Internet Engineering Task Force (IETF) is an open standards organization, which develops and promotes voluntary Internet standards, in particular the standards that comprise the Internet protocol suite (TCP/IP).
The International Standards Organisation (OSI) is a multinational organization that tries to standardize network communication protocols at the international level. OSI (Open System Interconnection) is a model that ISO put together as a networking communication standard.
The Internet Consortium for Assigned Names and Numbers (ICANN) controls the DNS hierarchy and the allocation of IP addresses

OSI and TCP/IP Layers & associated protocols

TCP/IP

A simple overview

TCP/IP

A bit more in depth

UDP vs TCP

A bit more in-depth than the video at the top of the web page

The 5 layer network model is the TCP/IP model.

Goes into detail with UDP and TCP protocols.

HTTP, HTTPS & SSL

FTP

POP3 vs IMAP

The Future and Protocols

From: APNIC - Internet protocols are changing

Background

When the Internet started to become widely used in the 1990s, most traffic used just a few protocols: IPv4 routed packets, TCP turned those packets into connections, SSL (later TLS) encrypted those connections, DNS named hosts to connect to, and HTTP was often the application protocol using it all.

For many years, there were negligible changes to these core Internet protocols.

As a result, network operators, vendors, and policymakers that want to improve (and sometimes, control) the Internet have adopted a number of practices based upon the official protocol to tweak things, whether intended to debug issues, improve quality of service, or impose policy.

Now, significant changes to the core Internet protocols are underway. While they are intended to be compatible with the Internet at large (since they won’t get adoption otherwise), they might be disruptive to those who have taken liberties with undocumented aspects of protocols or made an assumption that things won’t change.

Why we need to change the Internet

There are a number of factors driving these changes.

The limits of the core Internet protocols have become apparent, especially regarding performance. Because of structural problems in the application and transport protocols, the network was not being used as efficiently as it could be, leading to end-user perceived performance (in particular, latency).

This translates into a strong motivation to evolve or replace those protocols because there is a large body of experience showing the impact of even small performance gains.

The ability to evolve Internet protocols — at any layer — has become more difficult over time, largely thanks to the unintended uses by networks discussed above. For example, HTTP proxies that tried to compress responses made it more difficult to deploy new compression techniques; TCP optimization in middleboxes made it more difficult to deploy improvements to TCP.

Finally, we are in the midst of a shift towards more use of encryption on the Internet. Encryption is one of best tools we have to ensure that protocols can evolve and many protocols have been developed to insist on encryption.

You can read about these further by going to the APNIC site referenced above.

Determining the best network path

from CISCO

Determining the best path involves the evaluation of multiple paths to the same destination network and selecting the optimum or shortest path to reach that network. Whenever multiple paths to the same network exist, each path uses a different exit interface on the router to reach that network.

The best path is selected by a routing protocol based on the value or metric it uses to determine the distance to reach a network. A metric is the quantitative value used to measure the distance to a given network. The best path to a network is the path with the lowest metric.

Dynamic routing protocols typically use their own rules and metrics to build and update routing tables. The routing algorithm generates a value, or a metric, for each path through the network. Metrics can be based on either a single characteristic or several characteristics of a path. Some routing protocols can base route selection on multiple metrics, combining them into a single metric.

The following lists some dynamic protocols and the metrics they use:

Routing Information Protocol (RIP): Hop count
Open Shortest Path First (OSPF): Cisco routers use a cost based on cumulative bandwidth from source to destination
Enhanced Interior Gateway Routing Protocol (EIGRP): Bandwidth, delay, load, reliability