I'd like you to imagine that we've
discovered a malicious application that's
running on our network.
And so we talk to the security team,
and we asked them to block it so it can't course
through the veins of our network.
Now, in order to do their job, and to stop that traffic,
it's likely they're going to need
to know a few things including, number one, what
protocol or protocols is this application
or this malicious software using?
And secondly, what ports are involved?
Because there's going to be a big part of them implementing
controls to stop that type of traffic.
And even for applications and services
that are not malicious, it's handy for us
to know some of the common protocols and ports that
are used on our networks today.
So here's a nice handy table I'd like to just chat
with you about for a moment.
On the left-hand side, we have the actual protocol itself.
Then we have a little bit more information
here in this column in the middle.
And then over here, on the right,
we have some of the common well-known ports.
So if a user is going to the internet with a browser, it'
very likely they're going to using HTTP or HTTPS.
The big difference is one is plain text HTTP,
and the other has security services enabled as part of it.
And those protocols used TCP ports 80 and 443, respectively.
If a network administrator wanted to remotely connect over
to a router or a switch to do management on that,
they could remotely log on and get a command line interface.
They could type in characters, if you will,
to that system by using Telnet.
Telnet uses the well-known port at the transport layer
of TCP port 23.
However, because it's unencrypted, anybody who's
eavesdropping or who steals those packets off the network,
they'll be able to determine what's going on.
So most the time, for security, instead
of using Telnet, a more secure administrator
would be using SSH, Secure Shell, which
provides the same functionality of a remote connection
to a system, but it adds encryption and security
on top of it to make it more secure.
And SSH uses the well-known port of TCP 22.
When a computer is tyring to go to www.google.com,
in the background, that's being translated,
that name, into an IP address.
And that's an example of doing a DNS query
that our computer does behind the scenes for us
thousands of times a day.
And for that, at the transport layer,
it uses UDP as the transport protocol,
and port number 53 is the well-known port
for the DNS server.
In the world of TCP/IP, each host
is going to have an address.
We can assign IP addresses to clients
using a dynamic protocol called DHCP, the Dynamic Host
Configuration Protocol.
And that uses UDP port 67 and 68,
depending on if the packet from the client to the server
or response is coming from a DHCP server
going back to a DHCP client.
If we want to move files around, there's
lots of ways of doing it including these three
options right here--
FTP, File Transfer Protocol TFTP, Trivial File Transfer
Protocol, and SFTP, which, depending
on which protocol you're actually using
could be SSH file transfer protocol or secure file
transfer protocol.
And over here, in the right-hand column,
we have the common well-known ports associated
with those three protocols.
Another very common network service
is being used by millions of people every day is email.
And so we have several email protocols as well--
SMT, the Simple Mail Transfer protocol,
which is being used for outbound email or email that's
going back and forth between email servers.
We have Post Office Protocol version
3, or, POP which is a client application used to get email
from an email server.
We also have a protocol called IMAP, Internet Message Access
Protocol that can be used between an email client
and an email server for the retrieval and notifications
of email messages.
And those three protocols have three well-known ports
respectively associated with each of them.
Sometimes we need access to a remote device.
And one protocol we can use to do that
is RDP, Remote Desktop Protocol.
And it's well-known port is TCP port 3389.
Among the things we take for granted,
including accurate time, and most computer systems
are using, in the background, some flavor of NTP, Network
Time Protocol, which uses UDP port
123, as the well-known port associated with the NTP
server that can allow a computer to reach out, get the time,
and then synchronize its own time based on the server.
Another big advance over the last decade or so
in the world of IP networks is to have voice traffic
and telephone calls over IP networks.
And one of the protocols involved with that
is SIP, Session Initiation Protocol.
And well known ports associated with SIP
include TCP and UDP port 5060 as well as TCP port 5061.
A very popular protocol in a Microsoft network
that includes the ability to receive and send
files over the network is a protocol
called SMB, Server Message Block,
which is associated with the well known port of TCP 445.
One popular option of merging lots and lots of users
in an organization is to have a central repository
with all the users--
Bob, Sally, Lois, et cetera--
and then, whenever it needs to check and verify
things like passwords for those users,
they can check with that centralized server or servers.
And one protocol it can use to do that
is LDAP, the Lightweight Directory Access Protocol.
There is a version that does not use security
for the communications.
And there's, yet, another version
that does include the security.
And that's LDAPS, and that is for LDAP
that includes the benefits to TLS/SSL
for the protection of that communication when using LDAP.
So the less secure LDAP uses TCP and UDP port 389,
while LDAPS uses TCP port 636.
And the last protocol, on the list here I want to talk about,
is H.323, which is a whole suite of protocols
that can be used for audio and video over networks.
And some well-known ports associated with H.323
include UDP port 1719, TCP port 1720, and a boatload more.
And what you'll discover is that, as you
work with specific protocols more and more,
you'll become more and more familiar
with those specific ports used by those protocols.
I hope this has been informative for you.
And I'd like to thank you for viewing.