1
00:00:06,540 --> 00:00:10,770
- [Instructor] Servers Part
2: E-mail and Proxy Servers.

2
00:00:10,770 --> 00:00:13,650
An e-mail server stores and supplies

3
00:00:13,650 --> 00:00:17,250
incoming and outgoing e-mail to users

4
00:00:17,250 --> 00:00:20,490
and possibly to other e-mail servers.

5
00:00:20,490 --> 00:00:25,490
Common usages include POP3
accounts, IMAP accounts,

6
00:00:26,070 --> 00:00:30,300
and HTTPS connections
within a web browser.

7
00:00:30,300 --> 00:00:33,690
An e-mail server might
handle the sending of data,

8
00:00:33,690 --> 00:00:36,183
the receiving of data, or both.

9
00:00:37,260 --> 00:00:38,400
For the A-plus exams,

10
00:00:38,400 --> 00:00:43,400
you should know how to connect
a client to an e-mail server.

11
00:00:44,460 --> 00:00:49,460
This is done by using appropriate
e-mail client software

12
00:00:49,470 --> 00:00:51,540
such as Outlook,

13
00:00:51,540 --> 00:00:54,300
and knowing the server name,

14
00:00:54,300 --> 00:00:57,240
protocols, and ports to be used,

15
00:00:57,240 --> 00:00:59,190
the username and password,

16
00:00:59,190 --> 00:01:02,883
and whether there is any
additional security involved.

17
00:01:04,020 --> 00:01:05,670
One common example

18
00:01:05,670 --> 00:01:09,300
of an e-mail server is Microsoft Exchange,

19
00:01:09,300 --> 00:01:13,170
so very common to have
that with a Windows server.

20
00:01:13,170 --> 00:01:14,100
And so if we look here,

21
00:01:14,100 --> 00:01:18,270
we have our LAN and we
have our client computers,

22
00:01:18,270 --> 00:01:20,220
and we have two e-mail servers,

23
00:01:20,220 --> 00:01:23,730
one here which is located in the DMZ area

24
00:01:23,730 --> 00:01:25,710
on this side of the firewall,

25
00:01:25,710 --> 00:01:28,650
and one over here that's
just on the internet,

26
00:01:28,650 --> 00:01:30,570
out on the cloud.

27
00:01:30,570 --> 00:01:32,460
And you might have either of these

28
00:01:32,460 --> 00:01:34,860
in your company or organization,

29
00:01:34,860 --> 00:01:37,920
and there's different reasons for these.

30
00:01:37,920 --> 00:01:40,920
You might wanna have your
e-mail server internally

31
00:01:40,920 --> 00:01:42,120
for various reasons.

32
00:01:42,120 --> 00:01:43,140
And if you did,

33
00:01:43,140 --> 00:01:45,180
you'd wanna protect
that to a certain extent

34
00:01:45,180 --> 00:01:46,710
by placing it on a DMZ.

35
00:01:46,710 --> 00:01:49,110
You don't want it on the LAN.

36
00:01:49,110 --> 00:01:53,400
This way, clients on the LAN
can access the e-mail server,

37
00:01:53,400 --> 00:01:57,630
but those clients on the LAN
are protected by the firewall.

38
00:01:57,630 --> 00:02:01,440
Also clients out on the
cloud, out on the internet,

39
00:02:01,440 --> 00:02:04,620
can access the e-mail
server as well if necessary.

40
00:02:04,620 --> 00:02:07,680
People working from
home, people on the road.

41
00:02:07,680 --> 00:02:10,770
Or the e-mail server could
be stored on the internet,

42
00:02:10,770 --> 00:02:12,960
on the cloud altogether,

43
00:02:12,960 --> 00:02:15,810
and people access it
from wherever they are.

44
00:02:15,810 --> 00:02:19,440
At the workplace, at home,
on the road, and so on.

45
00:02:19,440 --> 00:02:20,460
And so you configure

46
00:02:20,460 --> 00:02:23,160
the client computer's
software like Outlook

47
00:02:23,160 --> 00:02:26,220
or whatever it is that
you're using to connect out

48
00:02:26,220 --> 00:02:28,050
to the e-mail server.

49
00:02:28,050 --> 00:02:31,470
And so let's say we were just
configuring a POP3 account.

50
00:02:31,470 --> 00:02:33,240
We'd have to set that up here,

51
00:02:33,240 --> 00:02:36,810
and we would need to know
the e-mail server's name,

52
00:02:36,810 --> 00:02:41,490
for example, mail.example.com,

53
00:02:41,490 --> 00:02:44,490
and we need to know that mail server name

54
00:02:44,490 --> 00:02:48,810
for POP3 and also for SMTP.

55
00:02:48,810 --> 00:02:51,450
Then we'd need to know the port numbers

56
00:02:51,450 --> 00:02:52,800
that those protocols are using.

57
00:02:52,800 --> 00:02:57,210
So for example, for secure
POP3, that would be 995.

58
00:02:57,210 --> 00:03:00,780
For secure SMTP, that would be 465.

59
00:03:00,780 --> 00:03:02,490
And then the username and password,

60
00:03:02,490 --> 00:03:05,430
and then we'd be able to connect
through to get our e-mail

61
00:03:05,430 --> 00:03:08,640
over the internet or
through the LAN to our DMZ,

62
00:03:08,640 --> 00:03:10,953
wherever that e-mail server is stored.

63
00:03:12,060 --> 00:03:16,260
Now, a proxy server is used
primarily as a go between

64
00:03:16,260 --> 00:03:19,500
for the client and the website accessed.

65
00:03:19,500 --> 00:03:22,800
It's commonly used to cached information

66
00:03:22,800 --> 00:03:26,490
so that another user
accessing the same webpage

67
00:03:26,490 --> 00:03:29,190
won't have to get it from the internet

68
00:03:29,190 --> 00:03:33,000
because it already exists
on the proxy server,

69
00:03:33,000 --> 00:03:36,063
which increases general
performance and efficiency.

70
00:03:37,050 --> 00:03:42,050
Most commonly, it's used
with HTTP and HTTPS,

71
00:03:42,390 --> 00:03:45,030
but it could be used by
other protocols as well,

72
00:03:45,030 --> 00:03:50,030
such as FTP and also
SMTP with e-mail servers.

73
00:03:51,930 --> 00:03:55,020
Examples of this include Squid,

74
00:03:55,020 --> 00:03:59,610
also Apache web server with
the appropriate proxy add-on,

75
00:03:59,610 --> 00:04:04,610
WinGate and the proxy
role in Windows Server.

76
00:04:05,010 --> 00:04:07,980
So you could use a Windows
server for that as well.

77
00:04:07,980 --> 00:04:09,360
So let's show how this works.

78
00:04:09,360 --> 00:04:13,200
Here, we have some computers
on the local area network,

79
00:04:13,200 --> 00:04:15,810
and we have a proxy server here as well.

80
00:04:15,810 --> 00:04:18,240
So let's say that one of these computers

81
00:04:18,240 --> 00:04:20,220
wanted to go to a website,

82
00:04:20,220 --> 00:04:23,373
and we'll just use
example.com as the example.

83
00:04:24,480 --> 00:04:29,310
That computer would go through
the proxy server every time

84
00:04:29,310 --> 00:04:32,493
and then out to the internet
and out to that website.

85
00:04:34,080 --> 00:04:37,590
That web information, that website page,

86
00:04:37,590 --> 00:04:39,600
would be stored at the proxy server

87
00:04:39,600 --> 00:04:41,403
and then forwarded to this client.

88
00:04:42,990 --> 00:04:44,760
Later, if another computer

89
00:04:44,760 --> 00:04:48,000
wanted to go to that same web server,

90
00:04:48,000 --> 00:04:50,700
it wouldn't actually have
to go out to the internet

91
00:04:50,700 --> 00:04:53,010
to get that homepage information

92
00:04:53,010 --> 00:04:55,473
because that is stored
at the proxy server.

93
00:04:56,580 --> 00:04:58,980
So that information would be forwarded

94
00:04:58,980 --> 00:05:01,230
by the proxy server to this client,

95
00:05:01,230 --> 00:05:03,120
and it'll effectively be faster

96
00:05:03,120 --> 00:05:05,520
and more efficient because of that.

97
00:05:05,520 --> 00:05:07,140
Now, on the client side,

98
00:05:07,140 --> 00:05:11,070
first of all you have to have
the server set up to do this,

99
00:05:11,070 --> 00:05:12,690
but you'd have to make the connections

100
00:05:12,690 --> 00:05:15,060
from the client side as well.

101
00:05:15,060 --> 00:05:17,130
So to do that in Windows,

102
00:05:17,130 --> 00:05:18,990
you would go to your Internet Properties,

103
00:05:18,990 --> 00:05:21,000
which you can get to from the browser

104
00:05:21,000 --> 00:05:22,740
or from the Control Panel.

105
00:05:22,740 --> 00:05:24,273
You would go to Connections,

106
00:05:25,200 --> 00:05:27,153
then you'd go to LAN settings,

107
00:05:28,410 --> 00:05:30,427
and then you would select Proxy server.

108
00:05:30,427 --> 00:05:33,510
"Use a proxy server for your LAN."

109
00:05:33,510 --> 00:05:36,120
And that's for this individual client.

110
00:05:36,120 --> 00:05:40,020
Then you'd need to know the IP
address of that proxy server,

111
00:05:40,020 --> 00:05:43,920
or the name, so that you could connect.

112
00:05:43,920 --> 00:05:45,420
And you'd type in the IP address

113
00:05:45,420 --> 00:05:48,300
and the ports you wanna
use with that proxy server.

114
00:05:48,300 --> 00:05:49,470
If we click on Advanced,

115
00:05:49,470 --> 00:05:51,510
we'll see we have multiple options here.

116
00:05:51,510 --> 00:05:54,480
We could do HTTP, which
is normally port 80.

117
00:05:54,480 --> 00:05:59,250
Secure, meaning SSL or TLS,
which is normally port 443.

118
00:05:59,250 --> 00:06:02,400
FTP and so on.

119
00:06:02,400 --> 00:06:04,350
Again, you just need to know the name

120
00:06:04,350 --> 00:06:06,810
or the IP address of that proxy server

121
00:06:06,810 --> 00:06:09,690
and the ports that it is using

122
00:06:09,690 --> 00:06:14,160
internally on the inbound side
to allow those connections.

123
00:06:14,160 --> 00:06:15,570
Once that's done,

124
00:06:15,570 --> 00:06:18,300
that connectivity could
be made from this computer

125
00:06:18,300 --> 00:06:19,800
through the proxy server,

126
00:06:19,800 --> 00:06:22,413
and you would set that up
on each of the clients.

127
00:06:23,850 --> 00:06:27,900
Now, proxy can also be used in reverse.

128
00:06:27,900 --> 00:06:29,790
To protect a web server,

129
00:06:29,790 --> 00:06:33,960
an organization might
implement a reverse proxy.

130
00:06:33,960 --> 00:06:37,710
This device is placed within
the area of the network

131
00:06:37,710 --> 00:06:40,203
where that web server resides.

132
00:06:41,220 --> 00:06:44,430
Requests from clients on the internet

133
00:06:44,430 --> 00:06:49,430
are forwarded by the reverse
proxy to the web server.

134
00:06:50,430 --> 00:06:54,510
This way, the clients are unaware

135
00:06:54,510 --> 00:06:57,183
of the web server's actual identity.

136
00:06:59,190 --> 00:07:01,380
Reverse proxies can also be used

137
00:07:01,380 --> 00:07:05,400
for encrypting the web
session through the internet

138
00:07:05,400 --> 00:07:07,680
and also load balancing

139
00:07:07,680 --> 00:07:10,620
where client requests can be distributed

140
00:07:10,620 --> 00:07:12,690
to multiple web servers.

141
00:07:12,690 --> 00:07:14,850
Let's say we had a very busy website.

142
00:07:14,850 --> 00:07:16,830
We might have three web servers

143
00:07:16,830 --> 00:07:20,250
that are mirrors of the same website.

144
00:07:20,250 --> 00:07:23,280
The reverse proxy would
select the web server

145
00:07:23,280 --> 00:07:26,460
that's being used the
least at the current time,

146
00:07:26,460 --> 00:07:30,300
so it balances the load
between web servers,

147
00:07:30,300 --> 00:07:32,430
especially when there's a lot of traffic

148
00:07:32,430 --> 00:07:34,383
over the internet to that website.

149
00:07:35,250 --> 00:07:37,470
Now, remember, the A-plus exams

150
00:07:37,470 --> 00:07:41,670
don't require in-depth
knowledge of servers,

151
00:07:41,670 --> 00:07:44,250
but make sure that you know the basics

152
00:07:44,250 --> 00:07:48,090
when it comes to e-mail
servers and proxy servers

153
00:07:48,090 --> 00:07:50,583
and their locations on the network.