diff options
| author | Sven Eisenhauer <sven@sven-eisenhauer.net> | 2023-11-10 15:11:48 +0100 |
|---|---|---|
| committer | Sven Eisenhauer <sven@sven-eisenhauer.net> | 2023-11-10 15:11:48 +0100 |
| commit | 33613a85afc4b1481367fbe92a17ee59c240250b (patch) | |
| tree | 670b842326116b376b505ec2263878912fca97e2 /Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html | |
| download | Studium-master.tar.gz Studium-master.tar.bz2 | |
Diffstat (limited to 'Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html')
| -rw-r--r-- | Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html b/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html new file mode 100644 index 0000000..d79bb1b --- /dev/null +++ b/Bachelor/CCNA4/en_CCNA4_v30/ch2/2_1_5/content.html @@ -0,0 +1,157 @@ +<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%">
+ <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</font></b><font face="Arial" size="2" color="#FFFFFF"><b>.1</b></font></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 Overview</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">
+ 2.1.5</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">Packet and circuit switching
+ </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">
+ Packet-switched networks were developed to overcome the expense of
+ public circuit-switched networks and to provide a more cost-effective
+ WAN technology.<p>When a subscriber makes a telephone call, the dialed
+ number is used to set switches in the exchanges along the route of the
+ call so that there is a continuous circuit from the originating caller
+ to that of the called party. Because of the switching operation
+ used to establish the circuit, the telephone system is called a
+ circuit-switched network. If the telephones are replaced with modems,
+ then the switched circuit is able to carry computer data.
+ <img border="0" src="../../images/1.gif" align="absmiddle" width="12" height="12"></p>
+ <p>The internal path taken by the circuit between exchanges is shared
+ by a number of conversations. Time division multiplexing (TDM) is
+ used to give each conversation a share of the connection in turn. TDM
+ assures that a fixed capacity connection is made available to the
+ subscriber. </p>
+ <p>If the circuit carries computer data, the usage of this
+ fixed capacity may not be efficient. For example, if the circuit is
+ used to access the Internet, there will be a burst of activity on the
+ circuit while a web page is transferred. This could be followed by no
+ activity while the user reads the page and then another burst of
+ activity while the next page is transferred. This variation in usage
+ between none and maximum is typical of computer network traffic.
+ Because the subscriber has sole use of the fixed capacity allocation,
+ switched circuits are generally an expensive way of moving data.</p>
+ <p>An alternative is to allocate the capacity to the traffic only when
+ it is needed, and share the available capacity between many users.
+ With a circuit-switched connection, the data bits put on the circuit
+ are automatically delivered to the far end because the circuit is
+ already established. If the circuit is to be shared, there must be
+ some mechanism to label the bits so that the system knows where to
+ deliver them. It is difficult to label individual bits, therefore they
+ are gathered into groups called cells, frames, or packets.
+ The packet passes from exchange to exchange for delivery through the
+ provider network. Networks that implement
+ this system are called packet-switched networks.
+ <img border="0" src="../../images/2.gif" align="absmiddle" width="12" height="12"></p>
+ <p>The links that connect the switches in the provider network belong
+ to an individual subscriber during data transfer, therefore many
+ subscribers can share the link. Costs can be significantly lower
+ than a dedicated circuit-switched connection. Data on packet-switched
+ networks are subject to unpredictable delays when individual packets
+ wait for other subscriber packets to be transmitted by a switch.</p>
+ <p>The switches in a packet-switched network determine, from
+ addressing information in each packet, which link the packet must be
+ sent on next. There are two approaches to this link
+ determination, connectionless or connection-oriented. Connectionless
+ systems, such as the Internet, carry full addressing information in
+ each packet. Each switch must evaluate the address to
+ determine where to send the packet. Connection-oriented systems
+ predetermine the route for a packet, and each packet need only carry
+ an identifier. In the case of Frame Relay, these are called Data Link
+ Control Identifiers (DLCI). The switch determines the onward route by
+ looking up the identifier in tables held in memory. The set of entries
+ in the tables identifies a particular route or circuit through the
+ system. If this circuit is only physically in existence while a packet
+ is traveling through it, it is called a Virtual Circuit (VC).</p>
+ <p>The table entries that constitute a VC can be established by
+ sending a connection request through the network. In this case the
+ resulting circuit is called a Switched Virtual Circuit (SVC). Data
+ that is to travel on SVCs must wait until the table entries have been
+ set up. Once established, the SVC may be in operation for hours, days
+ or weeks. Where a circuit is required to be always available, a
+ Permanent Virtual Circuit (PVC) will be established. Table entries are
+ loaded by the switches at boot time so the PVC is always available.</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>Packet vs Circuit Switching<p>
+ <a target="_blank" href="http://www.cina.org/ac051599/sld011.htm">
+ http://www.cina.org/ac051599/sld011.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>
\ No newline at end of file |