wideareanetworkingprotocol(ppt47)-经营管理(编辑修改稿)

wideareanetworkingprotocol(ppt47)-经营管理(编辑修改稿)内容摘要：

binterfaces on the serial line  Each subinterface uses a DLCI to represents the destinations for Frame Relay PVC work  Each subinterface uses its own subwork  Work for Partial mesh Frame Relay work  Configuring subinterfaces actually works to subdivide the Frame Relay work into smaller subworks.  Subinterfaces also solve the problem with routing protocols that use split horizon.  There are two types of subinterfaces:  Pointtopoint Used when a single virtual circuit connects one router to another. Each pointtopoint subinterface requires its own sub.  Multipoint Used when the router is the center of a star of virtual circuits. Uses a single sub for all routers’ serial interfaces connected to the frame switch. 来自 中国最大的资料库下载 Mapping Frame Relay  In order for IP devices at the ends of virtual circuits to municate, their addresses must be mapped to the DLCIs.  There are two ways to make this mapping happen:  Use the Frame Relay map mand for manually mapping. This is also the only way to configure multiple frame encapsulation types on an interface  Use the inversearp (by default enable) function to perform dynamic mapping of the IP address to the DLCI number but it’s not as stable as using the map mand because virtual circuits can be insidiously and dynamically mapped to unknown devices. 来自 中国最大的资料库下载 Frame Relay Configuration Tasks (1)  Router(configif  encapsulation framerelay [cisco|ietf]  Sets frame relay encapsulation for connection to nonCisco Routers (the default encapsulation is for same Cisco Routers)  Router(configif)  framerelay lmitype [ansi|cisco|q933a]  Selects LMI type  Beginning with IOS version , the LMI type is autosensed. This enables the interface to determine the LMI type supported by the switch.  Router(configif)  framerelay map protocol protocoladdress DLCI [cisco|ietf] [broadcast]  Defines how to reach a destination  The broadcast keyword at the end tells the router to forward broadcasts for this interface to this specific virtual circuit. Remember that Frame Relay is a nonbroadcast multiaccess (NBMA) encapsulation method, which will not broadcast routing protocols by default. 来自 中国最大的资料库下载 Frame Relay Configuration Tasks (2)  Router(config)  interface type.subinterfacenumber {pointtopoint|multipoint}  Creates the logical subinterface for Frame Relay  Generally the subinterface number matches the DLCI number but this is not a requirement – it only helps in the administration of the interfaces.  Router(configif)  framerelay interfacedlci dlci  Assigns a DLCI to the Frame Relay subinterface on the router 来自 中国最大的资料库下载 Frame Relay Congestion Control Frame Relay switch control congestion as follows:  DE (Discard Eligibility) When a Frame Relay router detects congestion on the Frame Relay work, it will turn the DE bit on in a Frame Relay packet header. If the switch is congested, the Frame Relay switch will discard the packets with the DE bit set first. If your bandwidth is configured with a CIR of zero, the DE will always be on.  FECN (ForwardExplicit Congestion Notification) When the Frame Relay work recognizes congestion in the cloud, the switch will set the FECN bit to 1 in a Frame Relay packet header. This will indicate to the destination DCE that the path just traversed is congested.  BECN (BackwardExplicit Congestion Notification) When the switch detects congestion in the Frame Relay work, it will set the BECN bit in a Frame Relay packet and send it to the source router, telling it to slow down the rate at which it is transmitting packets. 来自 中国最大的资料库下载 Committed Information Control (CIR)  Frame Relay is based on the assumption that not all customers need to transmit constant data all at the same time. Frame Relay works best with bursty traffic.  Frame Relay providers allow customers to buy a lower amount of bandwidth than what they really might need. This is called the Committed Information Rate (CIR).  The CIR specifies that as long as the data input by a device to the Frame Relay work is below or equal to the CIR, then the work will continue to forward data for the PVC. However, if data rates exceed the CIR, it is not guaranteed.  You can use a zero CIR to save money if retransmission of packets is acceptable. However, understand that the DE bit will always be turned on in every frame. 来自 中国最大的资料库下载 Monitoring Frame Relay  show framerelay lmi mand will give you the LMI traffic statistics exchanged between the local router and the Frame Relay switch.  show frame pvc mand will list all configured PVCs and DLCI numbers.  the status of each PVC connection and traffic statistics  the number of BECN and FECN packets received on the router  show interface mand displays line, protocol, DLCI, and LMI information  show frame map mand will show you the Network layer–to–DLCI mappings  debug frame lmi mand will show output on the router consoles by default. The information from this mand will allow you to verify and troubleshoot the Frame Relay connection by helping you to determine whether the router and switch are exchanging the correct LMI information 来自 中国最大的资料库下载 Integrated Services Digital Network (ISDN) Introduction to ISDN ISDN Components Basic Rate Interface (BRI) Primary Rate Interface (PRI) ISDN with Cisco Routers ISDN Configuration Tasks ISDN Configuration Example 来自 中国最大的资料库下载 Introduction to ISDN  A set of munication protocols proposed by telephone pany allowing digital services run over existing telephone works  Support data, text, voice, music, graphic and video transmission simultaneously, .  Highspeed image applications  Highspeed file transfer  Videoconferencing  Multiple links into homes of telemuters 。