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<title>SNA通过帧中继网</title>
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<p><font color="#008080" size="6"><em><strong><img
src="webimages/Sna_fr.GIF" width="300" height="64"></strong></em></font></p>
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<td><p align="right">帧中继具有的高<br>
速,低时延特性<br>
非常适合对时间<br>
敏感性很高的<br>
SNA网传输.这一<br>
章我们将介绍SNA<br>
数据透过帧中继<br>
网传输.包括为什<br>
么用帧中继传输<br>
SNA数据,好处,<br>
FEP Centric中<br>
BNN和BAN的概念<br>
及不同<br>
Router/FRAD <br>
Centric的实现.<br>
最后举例说明<br>
它们配置.</p>
</td>
<td> </td>
<td> </td>
<td><ul>
<li><a href="#pp1"><font color="#008080">介绍SNA透过帧中继传输</font></a><ul>
<li><a href="#pp2"><font color="#008080">为什么用帧中继传输SNA数据</font></a></li>
<li><a href="#pp3"><font color="#008080">RFC
1490</font></a></li>
</ul>
</li>
<li><a href="#pp4"><font color="#008080">路由器透过帧中继网访问前端处理器</font></a><ul>
<li><a href="#pp5"><font color="#008080">帧中继边界网络节点(BNN)</font></a></li>
<li><a href="#pp6"><font color="#008080">帧中继边界访问节点(BAN)</font></a></li>
</ul>
</li>
<li><a href="#pp7"><font color="#008080">路由器作FRAD设备访问前端处理器或Cisco
CIP卡</font></a></li>
<li><a href="#pp8"><font color="#008080">监控信息</font></a></li>
<li><a href="#pp9"><font color="#008080">配置实例</font></a></li>
</ul>
</td>
</tr>
</table>
<hr>
<p><a name="pp1"></a><font color="#008080" size="4"><em><strong>介绍SNA透过帧中继传输</strong></em></font></p>
<p>帧中继具有的高速,低时延特性非常适合对时间敏感性很高的SNA网传输.这一章我们将介绍SNA数据透过帧中继网传输.包括为什么用帧中继传输SNA数据,好处,FEP
Centric中BNN和BAN的概念及不同Router/FRAD Centric的实现.最后举例说明它们配置.</p>
<p><a name="pp2"></a><font color="#808080"><em><strong>为什么用帧中继传输SNA数据</strong></em></font></p>
<p>帧中继具有的高速,低时延特性非常适合对时间敏感性很高的SNA网传输.大家知道,SNA是发轮询信息确定下面PU设备是否处于激活状态的,由于网络数率,冲突等引起时延而使轮询应答超时是不必要的.帧中继另外提供许多好处为SNA传输:</p>
<ul>
<li>多种协议(SNA,IP,IPX,...)在一个PVC中运行<br>
SNA,IP,IPX,...</li>
</ul>
<ul>
<li>增强整体网络性能<br>
用高速帧中继链路代替低速专线.</li>
</ul>
<ul>
<li>降低网络使用费用<br>
帧中继价格较专线低.</li>
</ul>
<ul>
<li>未来升级容易<br>
IBM认可的易于升级到以后的ATM骨干网</li>
</ul>
<p><a name="pp3"></a><font color="#808080"><em><strong>RFC 1490</strong></em></font></p>
<p>RFC 1490定义了帧中继端到端的多协议打包方式.它支持SNA使用LLC2打包,实现链路层的排队,应答和流量控制.Cisco
IOS软件和NCP支持两种帧格式:</p>
<ul>
<li>RFC 1490 routed format for LLC2,在帧中继论坛FRF.3中详细说明,NCP端作BNN(Frame
Relay Boundary Network Node).需要NCP 7.1以上才支持.</li>
</ul>
<ul>
<li>RFC 1490 802.5 source-route bridged format,作BAN(Frame
Relay Boundary Access Node).需要NCP 7.3以上才支持.</li>
</ul>
<p><strong>RFC 1490 Routed Format for LLC2(BNN)</strong></p>
<p><img src="gif/s3217.gif" width="415" height="47"></p>
<p><strong>RFC 1490 Bridged Frame Format</strong></p>
<p><img src="gif/h7115.gif" width="328" height="293"></p>
<hr>
<p><a name="pp4"></a><font color="#008080" size="4"><em><strong>路由器透过帧中继网访问前端处理器(FEP
Centric)</strong></em></font></p>
<p><strong>FEP Centric</strong>指的是路由器在远端,透过帧中继网访问大机的前端处理器.可以实现多个协议在一条PVC中运行,线路费用也大大降低.</p>
<p><a name="pp5"></a><font color="#808080"><em><strong>帧中继边界网络节点(BNN)</strong></em></font></p>
<p>RFC 1490支持用LLC打包方式传输SNA数据,提供链路层次序,应答和流量控制.</p>
<p>相关的命令:</p>
<table border="2" bordercolordark="#808080"
bordercolorlight="#808080">
<tr>
<td>功能</td>
<td>命令</td>
</tr>
<tr>
<td>与一个帧中继DLCI的LLC连接</td>
<td><font face="Times New Roman"><strong>fras map llc</strong>
<em>mac-address lan-lsap lan-rsap</em> <strong>serial</strong>
<em>port</em> <strong>frame-relay</strong> <em>dlci
fr-lsap fr-rsap</em> [<strong>pfid2</strong> | <strong>afid2</strong>
| <strong>fid4</strong>] </font></td>
</tr>
<tr>
<td>与一个帧中继DLCI的SDLC连接</td>
<td><font face="Times New Roman"><strong>fras map sdlc</strong>
<em>sdlc-address </em><strong>serial</strong> <em>port </em><strong>frame-relay</strong>
<em>dlci fr-lsap fr-rsap</em> [<strong>pfid2</strong> | <strong>afid2</strong>
| <strong>fid4</strong>] </font></td>
</tr>
</table>
<p>请看配置实例"<a href="#pp11"><font color="#00FF00">BNN
Configuration (LAN) Sample</font></a>"和"<a
href="#pp15"><font color="#00FF00">BNN Configuration (SDLC)
Sample</font></a>".</p>
<p><a name="pp6"></a><font color="#808080"><em><strong>帧中继边界访问节点(BAN)</strong></em></font></p>
<p>BAN(Boundary Access Node)简化了路由器配置,当PU迁移,网卡变动不必象BNN那样改变路由器配置.</p>
<p>相关的命令:</p>
<table border="2" bordercolordark="#808080"
bordercolorlight="#808080">
<tr>
<td>功能</td>
<td>命令</td>
</tr>
<tr>
<td>帧中继BAN配置</td>
<td><font face="Times New Roman"><strong>fras ban</strong>
l<em>ocal-ring bridge-number ring-group ban-dlci-mac</em>
<strong>dlci</strong> <em>dlci#1 [dlci#2 . . . dlci#5] </em>[<strong>bni</strong>
<em>mac-addr</em>] </font></td>
</tr>
</table>
<p>请看配置实例"<a href="#pp12"><font color="#00FF00">BAN
Configuration (LAN) Sample</font></a>"和"<a
href="#pp16"><font color="#00FF00">BAN Configuration (SDLC)
Sample</font></a>".</p>
<hr>
<p><a name="pp7"></a><font color="#008080" size="4"><em><strong>路由器作FRAD设备访问前端处理器或Cisco
CIP卡</strong></em></font></p>
<p>我们可以用路由器作FRAD设备,串口直接连到帧中继网上,访问前端处理器或Cisco
CIP卡.</p>
<p>相关的命令:</p>
<table border="2" bordercolordark="#808080"
bordercolorlight="#808080">
<tr>
<td>功能</td>
<td>命令</td>
</tr>
<tr>
<td>指定DLSW+ remote peer</td>
<td><strong>dlsw remote-peer </strong><em>list-number </em><strong>frame-relay
interface serial </strong><em>number dlci-number</em></td>
</tr>
<tr>
<td>定义DLSw+和DLCI映射</td>
<td><strong>frame-relay map llc2 </strong><em>dlci-number</em></td>
</tr>
</table>
<p>请看"<a href="#pp13"><font color="#00FF00">DLSw+ Lite
Configuration Sample</font></a>"配置实例,具体请参阅<font
color="#00FF00"> </font><a href="dlsw.htm"><font color="#00FF00">DLSw+设计向导</font></a>.</p>
<p> </p>
<hr>
<p><a name="pp8"></a><font color="#008080" size="4"><em><strong>监控信息</strong></em></font></p>
<p>用show和debug监控网络信息.</p>
<ul>
<li><font face="Times New Roman"><em><strong>show fras</strong></em></font></li>
<li><font face="Times New Roman"><em><strong>show frame-relay
pvc</strong></em></font></li>
<li><font face="Times New Roman"><em><strong>show llc2</strong></em></font></li>
<li><font face="Times New Roman"><em><strong>debug
frame-relay llc</strong></em></font></li>
</ul>
<hr>
<p><a name="pp9"></a><font color="#008080" size="4"><em><strong>配置实例</strong></em></font></p>
<ul>
<li><a href="#pp10"><font color="#008080">LAN to Frame Relay</font></a><ul>
<li><a href="#pp11"><font color="#008080">BNN
Configuration(LAN)</font></a></li>
<li><a href="#pp12"><font color="#008080">BAN
Configuration(LAN)</font></a></li>
</ul>
</li>
<li><a href="#pp13"><font color="#008080">DLSw+ Lite
Configuration</font></a></li>
<li><a href="#pp14"><font color="#008080">SDLC to Frame Relay</font></a><ul>
<li><a href="#pp15"><font color="#008080">BNN
Configuration(SDLC)</font></a></li>
<li><a href="#pp16"><font color="#008080">BAN
Configuration(SDLC)</font></a></li>
</ul>
</li>
</ul>
<p><a name="pp10"></a><font color="#808080"><em><strong>LAN to
Frame Relay</strong></em></font></p>
<p><font color="#000000"><strong><img src="gif/s3219.gif"
width="461" height="170"></strong></font></p>
<p><a name="pp11"></a><font color="#000000"><strong>BNN
Configuration(LAN):</strong></font></p>
<p>interface tokenring 0<br>
no ip address<br>
no keepalive<br>
ring-speed 16<br>
fras map llc 0800.5a8f.8802 4 4 serial 0 frame-relay 16 4 4<br>
fras map llc 0800.5a8f.8804 4 4 serial 0 frame-relay 16 8 4<br>
fras map llc 0800.5a8f.8806 4 4 serial 0 frame-relay 17 4 4<br>
!<br>
interface serial 0<br>
mtu 2500<br>
no ip address<br>
encapsulation frame-relay IETF<br>
keepalive 12<br>
frame-relay lmi-type ansi<br>
frame-relay map llc2 16<br>
frame-relay map llc2 17</p>
<p><a name="pp12"></a><font color="#000000"><strong>BAN
Configuration(LAN):</strong></font></p>
<p>source-bridge ring-group 33<br>
!<br>
interface serial 0<br>
mtu 4000<br>
encapsulation frame-relay ietf<br>
frame-relay lmi-type ansi<br>
frame-relay map llc2 16<br>
frame-relay map llc2 17<br>
fras ban 34 11 33 4000.3745.0001 dlci 16 17<br>
!<br>
interface tokenring 0<br>
ring-speed 16<br>
source-bridge 32 10 33</p>
<p><a name="pp13"></a><font color="#000000"><strong>DLSw+ Lite
Configuration:</strong></font></p>
<p><font color="#000000"><strong><img src="gif/s3704.gif"
width="544" height="146"></strong></font></p>
<p>source-bridge ring-group 100<br>
dlsw local-peer peer-id 1.1.1.1<br>
dlsw remote-peer 0 frame-relay interface serial 0 30<br>
!<br>
interface tokenring 0<br>
ring-speed 16<br>
source-bridge active 1 1 100<br>
!<br>
interface serial 0<br>
mtu 3000<br>
no ip address<br>
encapsulation frame-relay<br>
frame-relay lmi-type ansi<br>
frame-relay map llc2 30</p>
<p><a name="pp14"></a><font color="#808080"><em><strong>SDLC to
Frame Relay</strong></em></font></p>
<p><font color="#000000"><strong><img src="gif/s3220.gif"
width="409" height="116"></strong></font></p>
<p><a name="pp15"></a><font color="#000000"><strong>BNN
Configuration(SDLC):</strong></font></p>
<p>interface serial 1<br>
no ip address<br>
encapsulation sdlc<br>
no keepalive<br>
clockrate 56000<br>
sdlc address C1<br>
sdlc xid C1 05D01501<br>
sdlc role primary<br>
fras map sdlc C1 serial 0 frame-relay 16 4 4<br>
!<br>
interface serial 0<br>
mtu 2500<br>
no ip address<br>
encapsulation frame-relay ietf<br>
keepalive 12<br>
frame-relay lmi-type ansi<br>
frame-relay map llc2 16</p>
<p><a name="pp16"></a><font color="#000000"><strong>BAN
Configuration(SDLC):</strong></font></p>
<p>source-bridge ring-group 666<br>
!<br>
interface serial 1<br>
no ip address<br>
encapsulation sdlc<br>
no keepalive<br>
clockrate 56000<br>
sdlc role primary<br>
sdlc traddress 4000.1000.1111 110 5 666<br>
sdlc address C1<br>
sdlc xid C1 05D01501<br>
sdlc partner 4000.1000.222 C1<br>
!<br>
interface serial 0<br>
mtu 2500<br>
no ip address<br>
encapsulation frame-relay ietf<br>
keepalive 12<br>
frame-relay lmi-type ansi<br>
frame-relay map llc2 16<br>
fras ban 120 1 666 4000.1000.2222 dlci 16</p>
<hr>
<p><img src="zijin%20copywrite.GIF" width="600" height="48"></p>
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