Frame Relay Learning (NA)

Background of Frame Relay generation:

1 Primary Two-point leased frame relay costs less

2 saving the interface of network devices

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, use Frame relay to create an extremely high-cost full-internetwork.

Example:

Suppose a company has three branch offices, if you use T1 Connect each branch office to the HQ, you need to occupy the three serial interface of the head office router. Now that you are using Frame Relay PVCs, each branch office can use T1 to connect to the service provider, as is the case with headquarters. In this case, the headquarters of the T1 line will have 3 PVC, one per branch office. Although there is only one acceptance and CSU/CDU of the headquarters, three PVC is like 3 separate links. 2 T1 interfaces and 2 csu/cdu are saved .

Term

Frame replayencapsulation Type (package type for Frame relay)

There are two kinds of package types for Frame Relay: Cisco and the IETF (Internet Engineering Task force). Default Usage Cisco, This is also the package type used when connecting Cisco devices . If you use Frame relay to connect Cisco devices and non-Cisco devices, you should use the package type IETF. regardless of which package type you use, you must keep both ends consistent.

Virtual Circles ( virtual circuit )

in any two DTE between Devices , Frame Relay provides a virtual circuit that looks like an actual circuit.

There are two kinds of virtual circuit, permanent virtual circuit (Permanent virtual circles) and switching virtual circuits (switched virtual circles.). The switching virtual circuit establishes this virtual circuit when there is data transmission. The data transfer is complete and can be removed .

Data Linkconnection identifies (DLCIs)

in Frame Relay. PVC is identified by using a data link link identifier. Typically, the Frame Relay service provider provides DLCI values.

Configuration statement: Router A (config-if): Frame-relayinterface-dlci 102

Inversarp Reverse ARP

ARP maps the MAC address to an IP address. the IARP runs on the frame relay circuit, maps the DLCI to an IP address, and lets frame relay know how to get to the other end of the PVC.

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1 R1 Issue query

2 Frame Relay switch informs the R1 (DLCI number)

3 Reverse ARP request (R1 issued), representing its identity

4 DLCI in Frame Relay switch query corresponding dlci- Physical Interface Association table (DLCI converted to R4 value of R2 to DLCI segment )

5 Reply (Response to Frame Relay switch DLCI value is 201)

6 the IP address corresponding to the DLC .

LMI ( Local management interface )

The local management interface is a signaling standard that is used between the local router and the first frame relay switch that it links to, allowing the provider network and DTE communicates information about the operation and status of virtual circuits.

Frame Relay Congestion Control ( Frame Relay congestion controller )

Discard Eligibility ( can be discarded ): It isknown that when a burst occurs (transmission packet exceeds The CIR of the PVC ), if the provider's network is in a congested state, exceeding the CIR groups can be discarded. Therefore, for an excess grouping, the DE is identified in the frame .

forward-showing congestion notification ( FECN aware that the switch will forward the frame relay header after the Frame relay network has been congested

-type congestion notification ( FECN) bit is set to 1to tell the destination DTEthat the frame passed through the path has been congested.

Back-congestion notification ( BECN) The switch detects that the frame relay network is congested and congestion occurs in front of the source router. However, after receiving this congestion message, Cisco routers will not take any action.

Frame Relay Learning (NA)