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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
|
<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns="http://www.w3.org/TR/REC-html40">
<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%">
<tr>
<td bgcolor="#336666" width="18" valign="top">
<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"><b><font face="Arial" size="2" color="#FFFFFF">2.2</font></b></td>
<td bgcolor="#336666"><img border="0" src="../../images/transdot.gif" width="10" height="1"></td>
<td bgcolor="#336666" width="100%">
<strong><font face="Arial" size="2" color="#FFFFFF">WAN Technologies</font></strong></td>
<td width="9" bgcolor="#336666"> </td>
</tr>
<tr>
<td bgcolor="#669999" height="25" width="18"> </td>
<td bgcolor="#669999" height="25"><b><font face="Arial" size="2" color="#FFFFFF">
2.2.6</font></b></td>
<td bgcolor="#669999"><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">ATM</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">Communications providers saw a need for a permanent shared
network technology that offered very low latency and jitter at much
higher bandwidths. Their solution
was Asynchronous Transfer Mode (ATM). ATM has data rates beyond 155
Mbps. As with the other shared technologies, such as X.25 and Frame
Relay, diagrams for ATM WANs look the same. <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></font><p>
<font face="Arial" size="2">ATM is a technology that is capable of
transferring voice, video, and data through private and public
networks. It is built on a cell-based architecture rather than on a
frame-based architecture. ATM cells are always a fixed length of 53
bytes. The 53 byte ATM cell contains a 5 byte ATM header followed by
48 bytes of ATM payload. Small, fixed-length cells are well suited for
carrying voice and video traffic because this traffic is intolerant of
delay. Video and voice traffic do not have to wait for a larger data
packet to be transmitted.</font></p>
<p>
<font face="Arial" size="2">The 53 byte ATM cell is less efficient
than the bigger frames and packets of Frame Relay and X.25.
Furthermore, the ATM cell has at least 5 bytes of overhead for each
48-byte payload. When the cell is carrying segmented network layer
packets, the overhead will be higher because the ATM switch must be
able to reassemble the packets at the destination. A typical ATM line
needs almost 20% greater bandwidth than Frame Relay to carry the same
volume of network layer data.</font></p>
<p>
<font face="Arial" size="2">ATM offers both PVCs and SVCs, although
PVCs are more common with WANs.</font></p>
<p>
<font face="Arial" size="2">As with other shared technologies, ATM
allows multiple virtual circuits on a single leased line connection to
the network edge.</font></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">
<a href="javascript:void(0)" onClick="window.open('../../activities/ch02/activity_2_2_6.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');">
<img border="0" src="../../images/media_icon.gif" width="25" height="25"></a> <b>
<a onClick="window.open('../../activities/ch02/activity_2_2_6.html','Interactivity','width=740,height=390,toolbar=0,resizable=yes,scrollbars=0,screenX=26,screenY=38,left=26,top=38');" href="javascript:void(0)">Interactive Media Activity</a></b></font></p>
</font><font FACE="Arial" SIZE="2" COLOR="#808080">
<p>Checkbox: WAN Technologies Asynchronous Transfer Mode (ATM)</p>
<p>Upon completing this activity, the student
will be able to identify the characteristics associated with ATM
connections.</p>
</font><font FACE="Arial" SIZE="2" COLOR="#000000">
<p><IMG alt="" height="2" width="1" src="../../images/s.gif"></p></TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
<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>Asynchronous Transfer Mode (ATM) Switching<p>
<a target="_blank" href="http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/atm.htm">
http://www.cisco.com/univercd/cc/
td/doc/cisintwk/ito_doc/atm.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 face="Arial" size="2"> </font>
</td>
</tr>
</table>
</body>
</html>
|
