>> Let's take a look at some of these protocols that
are a part of the TCP/IP suite.
The first one we'll take a look at is
FTP, File Transfer Protocol.
This is for uploading and downloading files.
A few things mentioned,
first there's a reference to the port numbers,
port 20 and 21.
We have to know those.
I also mentioned a specific fact about FTP.
It's not secure. Credentials traverse
the network in plain text.
So that's always going to be
a problem when you think about network security.
We don't ever want passwords
on the network in plain sight.
We really need to focus on securing the FTP,
which is coming up on the slide.
One of the tools that we can use to
secure FTP is a protocol called SSH.
SSH is Secure Shell.
Secure Shell is going to provide us
security over an unsecured network.
Secure Shell uses TCP port 22,
and this was designed to replace some of
the remote administration protocols,
like Telnet and FTP,
or if you work with Unix,
their utility is called the R utilities.
All of those have traditionally sent
passwords across the network in plain text.
By using SSH instead of plain FTP,
you get a more secure connection.
If you're replacing FTP with secure FTP,
then that now uses port 22,
also because SSH is really
the protocol that's providing
the transport and the security.
I will also mention that another protocol SCP,
Secure Copy Protocol,
uses SSH also port 22.
They love to ask questions about
this on the exam because it's
not just SSH that uses port 22,
it's SCP and S/FTP,
which can be something that's tricky to remember.
Make sure you know these.
Just spoke about Telnet and said
that Telnet is also another one of
those protocols that transmits
data across the wire and plain text.
We don't like that.
Telnet instead of telnetting into a system, we SSH.
Telnet uses TCP port 23.
SMTP, Simple Mail Transfer Protocol.
You have several different mail protocols.
What SMTP is for is sending
mail from mail server to mail server.
When you're talking about sending
mail from your system up
or from side-to-side, that's SMTP.
We've got other protocols that download
our mail for us or allow us to view our mail,
but when we're talking about sending, SMTP.
A friend of mine says to think of it
as send mail to people,
and that's exactly right.
SMTP though really stands for
Simple Mail Transfer Protocol, port 25.
Another protocol that we can look at
is really a protocol and a service.
It's called TACACS Plus.
TACACS Plus is port 49,
and this is a remote authentication server.
When clients are trying to access
your network from a remote location,
maybe they're connecting in a VPN,
a wireless access point,
even the back in the day when we used to dial up,
there needed to be a system
where we could centralize control,
and that system was TACACS Plus.
We'll talk about that more with
remote access in just a bit.
An important service on the network.
DNS, Domain Name Service,
or you could hear Domain Naming Service.
You and I like user-friendly names.
However, for systems to connect,
they need IP addresses.
We have to have some reference point
that we can go to and say,
"Hey, what's the IP address for weather.com?"
Or whatever it is we're looking for.
That's our DNS server.
Our DNS server provides us with
name resolutions that we can
connect to via IP address to host.
DNS works at port 53.
Now in a little bit,
we'll talk about the DNS database and how it works.
But for now, remote naming to
IP addresses, to IP addresses,
to user-friendly names, to IP addresses,
that's DNS port 53.
DHCP, another important network service.
DHCP provides IP addresses to clients automatically.
Rather than having an administrator
walk around from host to host,
IP not and an assigned IP address,
a client comes online,
pairs the DHCP server and gets an IP address.
That's very helpful.
One of the things we'll talk about is how
DHCP works and the process called DORA,
Discover Offer Requests Acknowledge.
That's coming up in just a bit.
DHCP operates on port 67 and 68.
Now an alternative to FTP,
we talked about this one a little bit earlier
when we were at Layer 4 of the OSI model.
We talked about an alternative to FTP called TFTP,
Trivial File Transfer Protocol.
TFTP is used in some environments when we're
looking to download operating systems for devices.
For example, if I'm doing an operating
system upgrade on a router or something,
I might use TFTP.
A lot of the times we think to use FTP or other means.
This is port 69, and if you'll remember,
the difference of TFP,
it piggybacks on UDP, which is connectionless.
FTP piggybacks on TCP,
which is connection oriented.
Lots of letters in this class.
[LAUGHTER] I hope you're keeping up.
HTTP, I think we're all
familiar with web traffic, Hypertext Transfer Protocol.
This is port 80.
If we're communicating with web traffic,
we're using port 80.
I'll mention that HTTP is not secure and in of itself.
We're going to have to add some security in just a bit.
For now, HTTP is port 80.
POP, Post Office Protocol.
I mentioned to you that SMTP was for sending mail.
When you're downloading email to your devices,
you're feeling those devices,
perhaps even on the server.
What we're looking at is using
>> one of the two protocols.
>> POP is very common and we're on Version 3, POP3.
There's also a protocol called IMAP,
which will come up in just a minute,
but that's Internet Mail Application Protocol.
That would be an alternative to POP3.
POP3 uses port 110.
Network Time Protocol.
Network Time Protocol is really important because it
controls the synchronization of devices on the network.
Many network services,
particularly Kerberos and several others,
require that our systems be in sync.
Network Time Protocol is
a service running on your domain controller that
helps ensure everybody's using
the same time clock and that we're synchronized.
NTP uses port 1,
2, 3. You know what?
I was going to tell you guys an NTP joke,
but my time is always off.
[LAUGHTER] I hope you enjoyed that.
I'll be here all week, folks.
There's our friend IMAP that we talked about earlier.
An alternative to POP.
Downloads mail from the server and uses port 143.
SNMP, Simple Network Management Protocol,
this is a protocol that
allows us to capture information on our networks,
that way we can monitor and be aware of
the traffic and the various events that are going on.
With SNMP, we have three main elements, an agent,
a central manager, and an MIB,
which is our management information base.
Our agent is whatever
network devices are running the SNMP software.
The central manager, which is ultimately
your management system that's
pulling all the information together,
and then our management information base.
All your agents contain
an information database specific to
the various parameters and
the information that's being captured.
This is the database that's used to request
the agent for specific information and
then make sure that information is transmitting
it and formatting in such a way that can be useful.
That's the management information database.
A Simple Network Management Protocol uses port 161.