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    <title>24-Port 4-Gbps Fibre Channel Module BB_Credit Buffers </title>
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<a name="wp1073118"> </a><h1 class="pTitle">
24-Port 4-Gbps Fibre Channel Module BB_Credit Buffers

</h1>
<a name="wp1073123"> </a><p class="pBody">
<a href="buffers13.html#wp1073127">Table&#160;14-6</a> lists the BB_credit buffer allocation for 24-port 4-Gbps Fibre Channel switching modules.

</p>
<a name="wp1073187"> </a><p class="pBodyRelative">
</p><div>
<table border="2" cellpadding="2" id="wp1073127table1073124">
  <caption><a name="wp1073127"> </a><div class="pTableTitle">
Table&#160;14-6	24-Port 4-Gbps Switching Module BB_Credit Buffer Allocation

</div>
</caption>
  <tr bgcolor="#CCCCCC" align="left" valign="middle">    <th colspan="1" rowspan="3"><a name="wp1073135"> </a><p class="pCellHeading">
BB_Credit Buffer Allocation

</p>
</th>
    <th colspan="3" rowspan="1"><a name="wp1073137"> </a><p class="pCellHeading">
BB_Credit Buffers Per Port

</p>
</th>
</tr>
  <tr bgcolor="#CCCCCC" align="left" valign="middle">    <th colspan="2" rowspan="1"><a name="wp1073145"> </a><p class="pCellHeading">
Dedicated Rate Mode

</p>
<a name="wp1073146"> </a><p class="pCellHeading">
4-Gbps Speed

</p>
</th>
    <th><a name="wp1073150"> </a><p class="pCellHeading">
Shared Rate Mode

</p>
<a name="wp1073151"> </a><p class="pCellHeading">
4-Gbps Speed

</p>
</th>
</tr>
  <tr bgcolor="#CCCCCC" align="left" valign="middle">    <th><a name="wp1073158"> </a><p class="pCellHeading">
ISL<a href="#wp1073157"><sup class="Footnote">1</sup></a>

</p>
</th>
    <th><a name="wp1073160"> </a><p class="pCellHeading">
Fx Port

</p>
</th>
    <th><a name="wp1073162"> </a><p class="pCellHeading">
Fx Port

</p>
</th>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1073164"> </a><p class="pBody">
Default BB_credit buffers

</p>
</td>
    <td><a name="wp1073166"> </a><p class="pBody">
250

</p>
</td>
    <td><a name="wp1073168"> </a><p class="pBody">
16

</p>
</td>
    <td><a name="wp1073170"> </a><p class="pBody">
16

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1073172"> </a><p class="pBody">
Maximum BB_credit buffers

</p>
</td>
    <td><a name="wp1073174"> </a><p class="pBody">
250

</p>
</td>
    <td><a name="wp1073176"> </a><p class="pBody">
250

</p>
</td>
    <td><a name="wp1073178"> </a><p class="pBody">
16

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1073180"> </a><p class="pBody">
Total number of BB_credits buffers per module

</p>
</td>
    <td colspan="3" rowspan="1"><a name="wp1073182"> </a><p class="pBody">
6000

</p>
</td>
</tr>
</table>

<table>
  <tr>
    <td><a name="wp1073157"> </a><p class="pTableFootnote">
<a href="#wp1073158"><sup class="Footnote">1</sup></a>ISL = E port or TE port.

</p>
</td>
  </tr>
</table>
</div>
<p class="pBodyRelative">
</p>
<a name="wp1073189"> </a><p class="pBody">
The following considerations apply to BB_credit buffers on 24-port 4-Gbps Fibre Channel switching 
modules:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1073190"> </a><li class="pSmartList1">BB_credit buffers for ISL connections can be configured from a minimum of 2 buffers to a 
maximum of 250 buffers for dedicated rate mode or 16 buffers for shared rate mode.
</li>
<a name="wp1073191"> </a><li class="pSmartList1">BB_credit buffers for Fx port mode connections can be configured. The minimum is 2 buffers and 
the maximum of 250 buffers for dedicated rate mode or 16 buffers for shared rate mode.
</li>
<a name="wp1073192"> </a><li class="pSmartList1">Performance buffers are not supported on this module.
</li>
</ul></div>
<a name="wp1073193"> </a><p class="pBody">
Each port group on the 24-port 4-Gbps Fibre Channel switching module consists of six ports. The ports 
in shared rate mode have a bandwidth oversubscription of 2:1 by default. However, some configurations 
of the shared ports in a port group can have a maximum bandwidth oversubscription of 4:1 (considering 
that each port group has 12.8-Gbps bandwidth). 

</p>
<a name="wp1073195"> </a><p class="pBody">
The following example configurations are supported by the 24-port 4-Gbps Fibre Channel switching 
modules:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1073196"> </a><li class="pSmartList1">Six ports with shared rate mode and 4-Gbps speed (2:1 oversubscription) (default) 
</li>
<a name="wp1073197"> </a><li class="pSmartList1">Two ports with dedicated rate mode and 4-Gbps speed plus <br />
four ports with shared rate mode and 4-Gbps speed (with 4:1 oversubscription)
</li>
<a name="wp1073198"> </a><li class="pSmartList1">One port with dedicated rate mode and 4-Gbps speed plus <br />
three ports with dedicated rate mode and 2-Gbps speed plus <br />
two ports with shared rate mode and 4-Gbps speed (4:1 oversubscription)
</li>
<a name="wp1073199"> </a><li class="pSmartList1">Six ports with dedicated rate mode and 2-Gbps speed
</li>
<a name="wp1073200"> </a><li class="pSmartList1">Three ports with dedicated rate mode and 4-Gbps speed plus<br />
three ports with shared rate mode and 1-Gbps speed 
</li>
</ul></div>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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