1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>Content</title>
<base target="_self">
</head>
<body background="../../images/bg.gif" topmargin="0" leftmargin="0" marginheight="0" marginwidth="0" onLoad="window.focus();" link="#808080" vlink="#808080" alink="#808080">
<table border="0" cellpadding="0" cellspacing="0" width="100%" height="53">
<tr>
<td bgcolor="#336666" width="18" valign="top" height="28">
<img border="0" src="../../images/content_lines.gif" width="16" height="25">
<img border="0" src="../../images/transdot.gif" width="2" height="1"></td>
<td bgcolor="#336666" height="28"><font face="Arial" size="2" color="#FFFFFF"><b>2.1</b></font></td>
<td bgcolor="#336666" height="28"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
<td bgcolor="#336666" width="100%" height="28"><strong>
<font face="Arial" size="2" color="#FFFFFF">WAN Technologies Overview</font></strong></td>
<td width="9" bgcolor="#336666" height="28"> </td>
</tr>
<tr>
<td bgcolor="#669999" height="25" width="18"> </td>
<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
2.1.1</font></b></td>
<td bgcolor="#669999" height="25"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
<td bgcolor="#669999" height="25" width="100%"><strong>
<font face="Arial" size="2" color="#FFFFFF">WAN technology</font></strong></td>
<td bgcolor="#669999" height="25" width="9"> </td>
</tr></table>
<table border="0" cellpadding="0" cellspacing="0" width="95%" bordercolor="#111111">
<tr>
<td width="15"></td>
<td>
<font FACE="Arial" SIZE="2">
A WAN is a data communications network that operates beyond the
geographic scope of a LAN. One primary difference between a WAN and a
LAN is that a company or organization must subscribe to an outside WAN
service provider in order to use WAN carrier network services. A WAN uses data
links provided by carrier services to access the Internet and connect
the locations of an organization to each other, to locations of other
organizations, to external services, and to remote users. WANs
generally carry a variety of traffic types, such as voice, data, and
video. Telephone and data services are the most commonly used WAN
services.</font><p>
<font face="Arial" size="2">Devices on the subscriber premises are
called customer premises equipment (CPE).
<img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"> The
subscriber owns the CPE or leases the CPE from the service provider. A
copper or fiber cable connects the CPE to the service provider�s
nearest exchange or central office (CO). This cabling is often called
the local loop, or "last-mile". A dialed call is connected locally to
other local loops, or non-locally through a trunk to a primary center.
It then goes to a sectional center and on to a regional or
international carrier center as the call travels to its destination.
<img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></font></p>
<p>
<font FACE="Arial" SIZE="2">
In order for the local loop to carry data, a device such as a modem is
needed to prepare the data for transmission. Devices that put data on
the local loop are called data circuit-terminating equipment, or data
communications equipment (DCE). The customer devices that pass the
data to the DCE are called data terminal equipment (DTE).
<img border="0" src="../../images/3.gif" align="absmiddle" width="12" height="12"> The DCE
primarily provides an interface for the DTE into the communication
link on the WAN cloud. The DTE/DCE interface uses various physical
layer protocols, such as High-Speed Serial Interface (HSSI) and V.35. These protocols establish the codes and
electrical parameters the devices use to communicate with each other.
<img border="0" src="../../images/4.gif" align="absmiddle" width="12" height="12"></font></p>
<p>
<font FACE="Arial" SIZE="2">
WAN links are provided at various speeds measured in bits per second
(bps), kilobits per second (kbps or 1000 bps), megabits per second
(Mbps or 1000 kbps) or gigabits per second (Gbps or 1000 Mbps). The
bps values are generally full duplex. This means that an E1 line can
carry 2 Mbps, or a T1 can carry 1.5 Mbps, in each direction
simultaneously.
<img border="0" src="../../images/5.gif" align="absmiddle" width="12" height="12"></p>
<p>
<TABLE bgcolor="#B0AFAF" width="95%" border="0" cellspacing="0" cellpadding="0">
<TR>
<TD valign="top">
<TABLE bgcolor="#669999" width="100%" cellspacing="0" cellpadding="0" border="0">
<TR>
<TD width="5">
<img border="0" src="../../images/lab_toplft.gif" width="116" height="23"></TD>
<TD><IMG alt="" height="1" width="3" src="../../images/s.gif"></TD><TD align="right" valign="top">
<IMG alt="" src="../../images/corner_ur_7.gif" width="7" height="7"></TD>
</TR>
</TABLE>
<TABLE bgcolor="#B0AFAF" width="100%" cellspacing="0" cellpadding="0" border="0">
<TR>
<TD>
<TABLE width="100%" cellpadding="2" cellspacing="0" border="0" bordercolor="#111111">
<TR>
<TD bgcolor="#ffffff" width="15"> </TD>
<TD bgcolor="#ffffff"><font FACE="Arial" SIZE="2" COLOR="#000000">
<p><font color="#808080">
<img border="0" src="../../images/links_icon.gif" width="25" height="25">
<b>Web Links</b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>Introduction to WAN Technologies<p>
<a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/introwan.htm">
http://www.cisco.com/univercd/cc/td/
doc/ cisintwk/ito_doc/ introwan.htm</a></font></p>
<p>
<IMG alt="" height="2" width="1" src="../../images/s.gif"></p>
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE><p>
</font>
</td>
</tr>
</table>
</body>
</html>
|
