Week 9 - Pre Networking

Created Wednesday 21 October 2020

Layers (OSI)

Application (HTTP, telnet, etc)
Presentation (framework MIME)
Session (pipe,SOCKS)
Transport (reliable packet delivery, TCP or UDP)
Network (nodes and address, IP)
Data (PPP)
Physical (wires, radio, USB)

Please Do Not Throw Sausage Pizza Away

Layers (OSI)

Application (HTTP, telnet, etc)
Presentation (framework MIME)
Session (pipe,SOCKS)
Transport (reliable packet delivery, TCP or UDP)
Network (nodes and address, IP)
Data (PPP)
Physical (wires, radio, USB)

NOTE - NEARLY EVERYTHING ABOVE PHYSICAL CAN
GET ALL JUMBLY AND SWITCHED AROUND


There is no cloud.


The Internet:

A bunch of computers connected together, that's it.

The ones in the middle do routing and transfer



IP addresses

Because numbers can be big, we could have a system that simply assigns
a unique number to every computer connected to the internet.

In fact we do, it's called IPv6

IP addresses

Because numbers can be big, we could have a system that simply assigns
a unique number to every computer connected to the internet.

In fact we do, it's called IPv6
(lOl wE DonT eveN UsE iT rEALly..
working on it, but we're still at about 94% the other thing

IP Addresses (IPv4)

4 billion oughta be enough, right? nooope, so we need NAT
Network
Address
Translation

This is what the ROUTERS do

if you see:
192.168.*.*
10.*.*.*
etc, these are "internal" networks. The routers do the job of subdividing

Internal networks

These can be deeply physical- pure wire

They can be wireless. Probably what you got at your house


And they can be virtual. VPN


What is a VPN again?

Badly named, of course:

//TECHNICALLY://
A Virtual Private Network

THE THING YOU SEE ADVERTISED
Uses VPN technology to act as a
QUASI-ANONYMOUS ENCRYPTED PROXY

So you could have a use/need for multiple VPNS

(and crappy Android only lets you have one, jerks, whats the deal with apple?)

(and you can mix up all these. I kind of know how and kind of don't)

One thing the above does: it mixes up the layers


TCP/IP AGAIN! (Your "new" VPN address)
-VPN (e.g. OpenVPN)
TCP (or UDP)/IP (with your "real" ip address / or router address)

(note, all are usually still valid by default unless your routing says otherwise)


TCP vs UDP


TCP - reliable handshake where you verify packets (SYN/ACK)
(important for encryption et al. VERIFICATION)
UDP - just spray them datas out there and see what happens
(cool for things like streaming, where the reassembly is heavy work by the computers)

TCP vs UDP



Tasteful Consensual Photos

(Hello, may I send you this?
Yes you may.
Here you go!
Thank you!)

TCP vs UDP


Unsolicited D(ramatic?) Pics

JUST BLASTIN PACKETS OUT THERE


SSH - another tool to do this sort of thing


SSH is a tool for directly (like by typing commands as if you were in front)
and INDIRECTLY (forwarding ports and services)

ssh -N -L 1993:outlook.office365.com:993
-L 1587:smtp.office365.com:587 pi@fib0

(real talk if you seriously need this holler at me)

PORTS

Somewhat like "telephone extensions" —
Or perhaps "doors vs. windows. vs garage doors vs. cargo doors, etc"

Further subdivides computer/IP addresses for purposes of separating concerns
e.g. We expect WEB traffic on 80 or 445 (though we can use a different one,
this is like climbing through a window even though there is a door)

PORTS

e.g.:

22 - SSH
80 - unencrypted Web
445 - encrypted Web
6881-6889 - Bittorrent


More on Ports

The CLASSICS:
21 - FTP
23 - Telnet
25 - SMTP (unencrypted)
53 - DNS (you shouldn't have this open)
90 - http (unencrypted)
110- POP
143 - IMAP (unencrypted)
3389 - RDP

Once again, a simple explanation of why Microsoft deserves to be bankrupt:

What's a good and easy way to secure a building? (assume locks work)

One way would be to lock all the doors and windows, and then only open the ones you need when you need to?

Reasonable and linuxy

Or you could do what Windows did


Once again

The reason for this mess.

A computer doesn't do anything unless it is told to.

The Windows people wrote the software this way:

Linux doesn't do this


And when it does, it's a mistake, not a design choice.

You have to MANUALLY turn on the programs that listen and obey orders.

(e.g. SSH or a web server, etc. Usually not the Microsoft backdoors, et al

but you know, those updates)

Cybersecurity words:

Open ports are now part of your "attack surface"

And you need to minimize that.

UPNP

Universal Plug 'n Play

Basically, the opposite of a firewall. Opens your router ports automatically


ROUTING:

Gateways, Addresses and Masks, oh my.

Routing works via Masks; i.e. if the first set of numbers matches a rule, you route that way..
If not, you go down the chain until something does, or you hit a default


ALSO OTHER STUFF


Hostnames

Locally, you can mostly pick your own.

Also, you may choose within a domain


DNS (Domain Name System)

Turns e.g. jrm4.com to 75.73.272.28

(hehe why is this fake for sure?)


Other Tools: TOR

TINC vpn


SSH

Default port 22
But, as mentioned last time, you *could* change it.
Some places will not allow you to.

This is a common attack surface, for obvious reasons —
This is the default method for "being in front" of a computer remotely.
(as mentioned before, you can also tunnel through here)



Backlinks: FSU Courses:LIS4774:RawSlides