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    <title>24-Port 8-Gbps Fibre Channel Module BB_Credit Buffers </title>
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    <blockquote>
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<a name="wp1072827"> </a><h1 class="pTitle">
24-Port 8-Gbps Fibre Channel Module BB_Credit Buffers

</h1>
<a name="wp1072831"> </a><p class="pBody">
<a href="buffers10.html#wp1072836">Table&#160;14-3</a> lists the BB_credit buffer allocation for the 24-port 8-Gbps Fibre Channel switching module.

</p>
<a name="wp1072912"> </a><p class="pBodyRelative">
</p><div>
<table border="2" cellpadding="2" id="wp1072836table1072832">
  <caption><a name="wp1072836"> </a><div class="pTableTitle">
Table&#160;14-3	24-Port 8-Gbps Switching Module BB_Credit Buffer Allocation

</div>
</caption>
  <tr bgcolor="#CCCCCC" align="left" valign="middle">    <th colspan="1" rowspan="3"><a name="wp1072844"> </a><p class="pCellHeading">
BB_Credit Buffer Allocation

</p>
</th>
    <th colspan="3" rowspan="1"><a name="wp1072846"> </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="wp1072854"> </a><p class="pCellHeading">
Dedicated Rate Mode

</p>
<a name="wp1072855"> </a><p class="pCellHeading">
8-Gbps Speed

</p>
</th>
    <th><a name="wp1072859"> </a><p class="pCellHeading">
Shared Rate Mode

</p>
<a name="wp1072860"> </a><p class="pCellHeading">
8-Gbps Speed

</p>
</th>
</tr>
  <tr bgcolor="#CCCCCC" align="left" valign="middle">    <th><a name="wp1072864"> </a><p class="pCellHeading">
ISL

</p>
</th>
    <th><a name="wp1072866"> </a><p class="pCellHeading">
Fx Port

</p>
</th>
    <th><a name="wp1072868"> </a><p class="pCellHeading">
Fx Port

</p>
</th>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1072870"> </a><p class="pBody">
Default BB_credit buffers

</p>
</td>
    <td><a name="wp1072872"> </a><p class="pBody">
500

</p>
</td>
    <td><a name="wp1072874"> </a><p class="pBody">
32

</p>
</td>
    <td><a name="wp1072876"> </a><p class="pBody">
32

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1072878"> </a><p class="pBody">
Maximum BB_credit buffers

</p>
</td>
    <td><a name="wp1072883"> </a><p class="pBody">
500<a href="#wp1114461"><sup class="Footnote">1</sup></a>

</p>
</td>
    <td><a name="wp1072885"> </a><p class="pBody">
500<sup class="cSuperscript">1
</sup>
</p>
</td>
    <td><a name="wp1072887"> </a><p class="pBody">
32

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td colspan="4" rowspan="1"><a name="wp1072889"> </a><p class="pCellHeading">
Total Number of BB_Credit Buffers per Module

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1072897"> </a><p class="pBody">
Ports 1 through 12

</p>
</td>
    <td colspan="3" rowspan="1"><a name="wp1072899"> </a><p class="pBody">
6000

</p>
</td>
</tr>
  <tr align="left" valign="top">    <td><a name="wp1072905"> </a><p class="pBody">
Ports 13 through 24

</p>
</td>
    <td colspan="3" rowspan="1"><a name="wp1072907"> </a><p class="pBody">
6000

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

<table>
  <tr>
    <td><a name="wp1114461"> </a><p class="pTableFootnote">
<a href="#wp1072883"><sup class="Footnote">1</sup></a>When connected to Generation 1 modules, reduce the maximum BB_credit allocation to 250.

</p>
</td>
  </tr>
</table>
</div>
<p class="pBodyRelative">
</p>
<a name="wp1072914"> </a><p class="pBody">
The following guidelines apply to BB_credit buffers on 24-port 8-Gbps Fibre Channel switching 
modules:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072915"> </a><li class="pSmartList1">BB_credit buffers allocated for ports 1 through 12 and 13 through 24 can be a maximum of 6000 
each so that the load is distributed.
</li>
<a name="wp1072916"> </a><li class="pSmartList1">BB_credit buffers for ISL connections can be configured from a minimum of 2 buffers to a 
maximum of 500 buffers for dedicated rate mode.
</li>
<a name="wp1072917"> </a><li class="pSmartList1">BB_credit buffers for Fx port mode connections can be configured. The minimum is 2 buffers and 
the maximum of 500 buffers for dedicated rate mode or 32 buffers for shared rate mode.
</li>
<a name="wp1072918"> </a><li class="pSmartList1">Performance buffers are not supported on this module.
</li>
</ul></div>
<a name="wp1072919"> </a><p class="pBody">
Each port group on the 24-port 8-Gbps Fibre Channel switching module consists of three ports. The ports 
in shared rate mode in a port group can have a maximum bandwidth oversubscription of 10:1 considering 
that each port group has 12.8-Gbps bandwidth. 

</p>
<a name="wp1072921"> </a><p class="pBody">
The following example configurations are supported by the 24-port 8-Gbps Fibre Channel switching 
modules:

</p>
<div class="pSmartList1"><ul class="pSmartList1">
<a name="wp1072922"> </a><li class="pSmartList1">Three ports with shared rate mode and 8-Gbps speed (2:1 oversubscription) (default)
</li>
<a name="wp1072923"> </a><li class="pSmartList1">One port with dedicated rate mode and 8-Gbps speed plus<br />
two ports with shared rate mode and 8-Gbps speed (4:1 oversubscription)
</li>
<a name="wp1072924"> </a><li class="pSmartList1">One port with dedicated rate mode and 8-Gbps speed plus <br />
one port with dedicated rate mode and 4-Gbps speed plus<br />
one port with shared rate mode and 8-Gbps speed (10:1 oversubscription)
</li>
<a name="wp1072925"> </a><li class="pSmartList1">Two ports with dedicated rate mode and 4-Gbps speed plus<br />
one port with shared rate mode and 8-Gbps speed (2:1 oversubscription)&#160;
</li>
<a name="wp1072926"> </a><li class="pSmartList1">Three ports with dedicated rate mode and 4-Gbps speed
</li>
</ul></div>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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