综合业务数字网 （Intergrated Services Digital Network,ISDN) 第十八章 综合业务数字网 （Intergrated Services Digital Network,ISDN)

ISDN的起源和优点 ISDN起源于1968年 当时人们预测它将访问集成到广泛的服务的范围（语音、网络互联、报文交换和有线电视） 1、连接建立极快 2、比租用线路费用底 3、比模拟线路的传输速度更快

什么是 ISDN ISDN 能够提供声音、视频、数据等传输服务 Small office Digital PBX Provider network Telecommuter Purpose: this figure describes various ISDN environments. Emphasize: The icons in the cloud represent ISDN switches. The figure displays different sites that may use ISDN. Home office Central site ISDN 能够提供声音、视频、数据等传输服务

ISDN的两种服务方式 ISDN服务根据不同的信道数目分为： 1、BRI (Basi Rate Interface) 典型的ISDN BRI服务提供两个B信道和一个D信道 （2B+D） 应用于小型企业或家庭； 2、PRI（Primary Rate Interface） [北美和日本]提供的ISDN PRI服务提供二十三个B信道和一个D信道 （23B+D）速率可达1.544Mbps [欧洲]提供的ISDN PRI服务提供三十个B信道和一个D信道（30B+D） 速率可达2.048Mbps 应用于大型企业，PRI通过利用多个信道捆绑在一起，来实现高带宽 的网络环境。

Signaling information (LAPD) ISDN 访问方式 Channel Capacity Mostly Used for B 64 kbps Circuit-switched data (HDLC, PPP) D 16/64 kbps Signaling information (LAPD) BRI NT1 D 2B Service provider network Purpose: The figure explains BRI and PRI. Emphasize: Be aware of geographic variations regarding ISDN services. With PRI, for example, there are 23 B channels in the United States and Japan and 30 in Europe. Highlight that LAPD is the data link protocol on the D channel and PPP is typically seen on the B channels. PRI CSU/DSU D 23 or 30B BRI 和 PRI 是ISDN的两种常见访问方式

BRI 呼叫处理 ISDN service provider 1 3 4 ISDN Switch ISDN Switch 2 SS7 Purpose: This figure describes the ISDN BRI call setup process. Emphasize: The D channel is always up. The D channel is the signaling channel. The B channels are used to send data. 2 SS7 B channel(s) D channel/SS7 signaling

Service provider network ISDN 功能和参考点 Local loop TE1 NT2 NT1 Service provider network S T U ISDN Terminal TE2 R TA 硬件设备的主要功能 参考点的划分和不同的接口 Purpose: This figure highlights ISDN hardware standards and reference points. Emphasize: The TE1 designates a native ISDN device that can connect directly to its S/T interface. The TE1 characterizes a Cisco router that has a BRI. The NT1 is a required external device that converts the 4-wire connection on the T interface to a 2-wire U line interface. The U interface also ensures rate conversion, clock synchronization, frame alignment, and adequate power supply, an provides an operational and maintenance control point for the service provider. The TE2 designates a nonnative ISDN device that requires a TA for its S interface signals. The TE2 characterizes a Cisco router without a BRI. The TA is an external device required on nonnative ISDN devices. The TA adapts the standard R-type device signals (RS-232, V.35, and so on) for the ISDN S/T interface. The S interface enables the connection for user devices and provides access the the useful transmission rate (for example, 144 kbps for BRI). The T interface corresponds to the S interface from the provider perspective. The T interface offers the total transmission rate (for example, 192 kbps from 2B*64+1D*16+1Y*48). There is also a V interface that is part in the ISDN cloud. It is not covered here because it does not affect the CPE side of the connection Terminal Adapter Existing Terminal

Service provider network Cisco ISDN BRI 接口 Native ISDN interface—int bri 0 Service provider network TE1 bri 0 NT1 S/T Purpose: This figure further highlights ISDN hardware standards and reference points for native and non-native ISDN devices. Emphasize: Non-native ISDN devices, TE2s lack an ISDN BRI interface. To configure this device add an external TA to the serial interface; the TA contains the BRI S/T interface. If the router does not have an NT1 interface, an external one must be provided. A simple way to check if the router is equipped with a built in NT1 is to check if it has an S/T or U interface. If the router has an S/T interface, it does not have a built in NT1. If it has a U interface, it has a built in NT1. Note: Never connect a router with a U interface to an NT1 device because it could result in problems with the hardware. NT1 TE1 bri 0 TE2 S/T R TA NT1 U S0 Nonnative ISDN interface—int serial 0 (EIA/TIA-232, V.35, X.21)

什么是按需拨号路由(DDR) 需要时建立连接 数据通讯完成时切断 ISDN 或 PSTN Dallas Corporate PSTN Chicago ISDN I need to send data to Dallas. Purpose: This figure introduces students to DDR. Emphasize: Explain that DDR is used to refer to a collection of dialup features. 需要时建立连接 数据通讯完成时切断 ISDN 或 PSTN

何时使用 DDR 定期连接 小数据量传输 Telecommuter Headquarters Vendor Purpose: This figure explains when one would want to use DDR. Emphasize: DDR is used for low-volume, periodic connections when traffic demands do not dictate the use of a dedicated line. DDR addresses the need for periodic network connections over a circuit-switched WAN service. By using WAN connections only on an as-need basis, DDR saves WAN-usage costs. Note: Provide some scenarios when DDR may be used. Headquarters 定期连接 小数据量传输 Vendor

“Interesting” packet arrives DDR 工作过程 “Interesting” packet arrives DCE 1. 决定目标路径 Layer 1 of 4: Purpose: This figure explains DDR operation. Emphasize: Layer 1 shows interesting packets arriving at the router.

“Interesting” packet arrives DDR 工作过程 “Interesting” packet arrives DCE 1. 决定目标路径 2. 指明建立 DDR 通话的触发条件 Layer 2 of 4: Purpose: This figure explains DDR operation. Emphasize: Layer 2 shows the router looking for a route to a destination. Introduce the concept of “interesting” traffic. This traffic is defined by some criteria, such as a particular kind of protocol or being permitted by an access list. Once this traffic has been identified, the router can monitor for interesting packets.

“Interesting” packet arrives DDR 工作过程 “Interesting” packet arrives Dial connection ISDN or Basic Service DCE 1. 决定目标路径 2. 指明建立 DDR 通话的触发条件 3. 检查拨号信息 Layer 3 of 4: Purpose: This figure explains DDR operation. Emphasize: Layer 3 adds “dial connection” and dashed WAN connection between routers. The DCE device places a call to a predefined destination.

“Interesting” packet arrives DDR 工作过程 “Interesting” packet arrives Dial connection ISDN or Basic Service DCE 1. 决定目标路径 2. 指明建立 DDR 通话的触发条件 3. 检查拨号信息 4. 数据传输 5. 会话结束 Layer 4 of 4: Purpose: This figure explains DDR operation. Emphasize: Layer 4 adds fourth and fifth lines. After a user-defined idle period, the call is disconnected. Point out that static routes are configured between the routers to avoid periodic transmissions over the WAN that would be caused by dynamic routing.

“Interesting” packet arrives 配置 DDR “Interesting” packet arrives DCE Layer 1 of 3: Purpose: This figure explains how to configure Legacy DDR. Emphasize: It is important to note that these configuration steps are aligned with how the router processes a DDR call (refer to the “DDR Operation” discussion. In layer 1, you must define the static route. 1 指定静态路由—使用哪条路由?

“Interesting” packet arrives 配置 DDR “Interesting” packet arrives DCE Layer 2 of 3: Purpose: This figure explains how to configure Legacy DDR. Emphasize: In layer 2, you must define “interesting” traffic by specifying a protocol or access list. 1 指定静态路由—使用哪条路由? 指定触发数据—什么样的数据能够建立连接? 2

“Interesting” packet arrives 配置 DDR “Interesting” packet arrives Dial connection ISDN or Basic Service DCE Layer 3 of 3: Purpose: This figure explains how to configure Legacy DDR. Emphasize: Configure the dialer information. 1 指定静态路由—使用哪条路由? 指定触发数据—什么样的数据能够建立连接? 配置拨号信息—播叫哪个号码? 2 3

任务 1: 指定路由信息 ISDN ip route 10.40.0.0 255.255.0.0 10.1.0.1 Subnet 10.40.0.0 10.1.0.1 10.1.0.2 Subnets 10.10.0.0 10.20.0.0 ISDN Home Central bri 0 5551000 bri 0 5552000 ip route 10.40.0.0 255.255.0.0 10.1.0.1 Purpose: This figure reviews how to configure a static route. Emphasize: Static routes were covered in the “Determining IP Routes” chapter. Static routes are commonly used with DDR. Dynamic routing protocols are not commonly used with DDR because the line could come up every time there is a routing update. Specify address of next hop router ip route 10.10.0.0 255.255.0.0 10.1.0.2 ip route 10.20.0.0 255.255.0.0 10.1.0.2 Network prefix and prefix mask

任务 2: 指定触发条件 没有访问列表 所有的数据都可以建立连接 有访问列表 Deny FTP Deny Telnet dialer-list 1 protocol ip permit 所有的数据都可以建立连接 有访问列表 Purpose: This figure explains how to specify interesting traffic on a Cisco router. Emphasize: This step involves some planning because access lists allow for much flexibility. You must know exactly what kind of traffic should engage the line. The dialer-list protocol command identifies interesting traffic based on protocol type. It can be used to specify an entire protocol suite. It can also be used to link an access list that more narrowly defines interesting packets to a dialer group. dialer-list 1 protocol ip list 101 access-list 101 deny tcp any any eq ftp access-list 101 deny tcp any any eq telnet access-list 101 permit ip any any Deny FTP Deny Telnet 除了FTP和Telnet以外的数据都可以建立连接

任务 3: 配置拨号信息 这两个值要匹配 根据实际情况在端口上设置拨号信息 hostname Home ! isdn switch-type basic-5ess interface BRI0 ip address 10.1.0.1 255.255.255.0 encapsulation ppp dialer idle-timeout 180 dialer map ip 10.1.0.2 name Central 5552000 dialer-group 1 no fair-queue ppp authentication chap router rip network 10.0.0.0 no ip classless ip route 10.10.0.0 255.255.0.0 10.1.0.2 ip route 10.20.0.0 255.255.0.0 10.1.0.2 dialer-list 1 protocol ip permit 根据实际情况在端口上设置拨号信息 Purpose: This figure explains how to configure the dialer interface. Emphasize: Remind students to configure PPP on the dialer interface as they did on the serial interface in the “Establishing Serial Point-to-Point Connections” chapter. PPP is the data link protocol operating on the B channels. The dialer-group command assigns an interface to a dialer access group (specified with the dialer-list command), and connects the interface to access list statements that identify interesting protocol traffic. You can apply the same dialer list to one or more interfaces. 这两个值要匹配

任务 3: 配置拨号信息 How do I get to subnetwork 10.10.0.0? ISDN Number to dial 10.1.0.1 10.1.0.2 Subnets 10.10.0.0 10.20.0.0 ISDN Home Central bri 0 5551000 bri 0 5552000 interface BRI0 ip address 10.1.0.1 255.255.255.0 encapsulation ppp dialer idle-timeout 180 dialer map ip 10.1.0.2 name Central 5552000 dialer-group 1 no fair-queue ppp authentication chap Purpose: This figure further explains how to configure the dialer interface. Emphasize: The dialer-map command maps the remote protocol address to a telephone number. You need this command if you will be dialing multiple sites. If you will be dialing only one site, you could use and unconditional dialer string command that always dials the one phone number regardless of the traffic destination. Note: This step is unique to Legacy DDR. Although the information is always required, the steps to configure destination information are different if using dialer profiles instead of Legacy DDR. If you are dialing only one site, you could use the dialer-string command, although this method is rarely used because it does not allow for authentication. Number to dial Remote host name Used for PPP CHAP

DDR 配置总述 3 1 2 hostname Home ! isdn switch-type basic-5ess interface BRI0 ip address 10.1.0.1 255.255.255.0 encapsulation ppp dialer load-threshold 125 either dialer idle-timeout 180 dialer map ip 10.1.0.2 name Central 5552000 dialer-group 1 ppp authentication chap router rip network 10.0.0.0 no ip classless ip route 10.10.0.0 255.255.0.0 10.1.0.2 ip route 10.20.0.0 255.255.0.0 10.1.0.2 dialer-list 1 protocol ip permit 3 Purpose: This figure summarizes the tasks just presented. Emphasize: Many times a configuration can look very confusing and complex. This page attempts to simplify the DDR configuration by showing a comprehensive configuration and matching the commands to the tasks just discussed. Match the commands to the configuration tasks. 1 2

DDR 配置命令 设置启用第二个通道传输数据的条件 设置会话切断前的延迟时间 Router(config-if)#dialer load-threshold load [ outbound | inbound | either ] 设置启用第二个通道传输数据的条件 设置会话切断前的延迟时间 Purpose: This figure presents some optional DDR commands. Emphasize: The dialer idle-timeout as a default value of 120. The dialer idle-timeout command specifies the amount of time the link stays idle before the connection is terminated. The dialer idle-timeout command is like a stopwatch. When the last interesting packet leaves the router, the router sets a timer to measure how long the interface is idle (defined by the absence of interesting traffic). If interesting traffic arrives, the timer is reset. If no interesting packets arrive at the interface before the timer expires, then the call is hung up even if non-interesting traffic is on the line. The dialer load-threshold controls the conditions under which another call can be placed to the same destination. If you had too much traffic trying to squeeze over one phone line, then based on this parameter you may wish to place another simultaneous call to increase your bandwidth. In releases before 11.1, load was only monitored in the outgoing direction. Router(config-if)#dialer idle-timeout seconds

DDR 配置举例 ISDN Access list defining interesting packets on Cisco A access-list 101 permit tcp any any eq smtp access-list 101 permit tcp any any eq telnet dialer-list 1 protocol ip list 101 ! ip route 192.168.12.0 255.255.255.0 10.108.126.2 ip route 192.168.14.0 255.255.255.0 10.108.126.2 ! interface bri 0 ip address 10.108.126.1 255.255.255.0 dialer-group 1 dialer map ip 10.108.126.2 name B 5551234 ! dialer idle-timeout 300 Access list defining interesting packets on Cisco A Static routes to reach destination Interface configuration for DDR Purpose: This figure explains how to use access control lists with DDR. Time to wait before dropping call 10.108.126.1 10.108.126.2 Subnets 192.168.12.0 192.168.14.0 ISDN A B

查看ISDN 信息 触发线路的连接 显示线路的连接状态 使用ISDN 时, 会话建立时的状态显示 显示 ISDN 的连接状态 显示路由表 Router#ping or telnet 显示线路的连接状态 Router#show dialer 使用ISDN 时, 会话建立时的状态显示 Router#show isdn active Purpose: This figure highlights some of the verification commands used in ISDN. Emphasize: Summarize the commands shown and provide examples of when each is used. 显示 ISDN 的连接状态 Router#show isdn status 显示路由表 Router#show ip route

查看ISDN 信息 显示 ISDN 第二层信息 显示 ISDN 会话建立和切断情况 显示会话建立和切断状态 在端口上清除已经建立的连接 Router#debug isdn q921 显示 ISDN 第二层信息 Router#debug isdn q931 显示 ISDN 会话建立和切断情况 Router#debug dialer Purpose: This figure further highlights some of the verification commands used in ISDN. Emphasize: Summarize the commands shown and provide examples of when each is used. 显示会话建立和切断状态 Router(config-if)#shutdown 在端口上清除已经建立的连接