ccna chapter 11 by jetarvind kumar madhukar

Release 16/07/2009 Jetking Infotrain Ltd.

Establishing Frame Relay Connection

Chapter 11

Release 16/07/2009Jetking Infotrain Ltd.

Chapter Objectives

Discuss the Frame Relay components Explain virtual circuit Explain LMI configuration and Encapsulation Explain DLCI addressing details Explain concerns of network layer and frame layer Troubleshoot LMI Configure Frame Relay


Recall - I

Speed, Multiple Device Support, Inexpensive are The features of ISDN are

Network Termination Device 1 (NT1), Network Termination Device 2 (NT2), ISDN Router, Terminal Equipment 1 (TE1), Terminal Equipment 2 (TE2), Terminal Adapter (TA) are e ISDN devices

ISDN is a channelized service. A channelized service splits a wire into many logical channels or time slots


Recall - II

ISDN supports two types of connections such as the Basic Rate Interface (BRI) and Primary Rate Interface (PRI)

You can verify the ISDN connections using two commands: show interface command show isdn status command


Frame Relay

Features of Frame Relay Operates at a higher speed (44.3 Mbps) Operates only in physical and data link layers Is less expensive than other WAN connection

such as X.25 Has error detection at the data link layer only Provides faster transmission for media that are

more reliable and protocols that have flow and error control at the higher layers


Frame Relay Components - I


Frame Relay Components - II

The basic terms associated with the Frame Relay network are as follows: Data Terminal Equipment (DTE) Data Communications Equipment (DCE) Access link Local access rate DLCI LMI Committed Information (CIR)


Frame Relay Components - III

Committed burst (Bc) Excess Burst (Be) Forward explicit congestion notification (FECN) Backward explicit congestion notification (BECN) Discard Eligibility (DE) indicator


Logical Connectivity of Frame Relay Network


Committed Information Rate (CIR) Frame Relay allows multiple users to use the packet

switched network at the same time The only limitation of Frame Relay is that not all

users can transmit the data at the same time Frame Relay provides dedicated bandwidths to all

the users for data transmission The Frame Relay can function as a leased line if the

access rate and CIR values are same


Standard Frame Relay Frame Structure The frame format allows you to understand the functionality of Frame

Relay Each frame has flags that indicate the start and end of the frame


Frame Relay Encapsulation Types The Frame Relay has two types of encapsulations

that you can view using the encapsulation frame-relay ? command: Cisco Internet Engineering Task Force (IETF)

The devices in a network can communicate only if their Frame Relay encapsulation types are same


Virtual Circuit

A Virtual Circuit (VC) represents the path on which the frame travels. Virtual circuits enable you to compare Frame Relay to leased physical circuit

There are two types of virtual circuits, such as: Permanent Virtual Circuit (PVC) Switched Virtual Circuit (SVC)


Virtual Circuits


Partial Mesh Network


LMI Configuration and Encapsulation LMI is the signaling standard used between the

Frame Relay DTE and Frame Relay DCE LMI is the communication between the router and

the nearest Frame Relay switch The LMI performs the following functions:

Implements a keepalive function to verify the flow of data between the DTE and DCE

Informs whether Permanent Virtual Circuit (PVC) is active or not


LAPF Header


Identifying the type of protocol If the Frame Relay is using the LAPF header then

the DTEs cannot support multiprotocol traffic because there is no way to identify the type of protocol

To solve this problem. Cisco Encapsulation and RFC 1490 Encapsulation is used


Cisco Encapsulation


RFC 1490 Encapsulation


DLCI Addressing


DLCI Addressing Details

The exact number of DLCI is dependent on the following factors: Protocols being routed Broadcast traffic Speed of line Static Routes Size of routing protocol and SAP updates


Frame Relay involves following issues related to the transmission of data packets from the layer 3 across the network: Layer 3 addressing with Frame Relay Broadcast handling

Concerns of Network Layer and Frame Relay


Frame Relay Layer 3 Addressing The Frame Relay implementation of Cisco provides

three different options to assign subnets and IP address on the Frame Relay interfaces. The options are: A subnet that contains all the Frame Relay Data

Terminal Equipments (DTE) A subnet for each virtual circuit Hybrid of the above two options


Full Mesh Network


Partial Mesh Network


Hybrid Network


Broadcast Handling

The Frame Relay can send copies of broadcast over all the virtual circuits

The Frame Relay does not have the capability to replicate and deliver across multiple virtual circuits to several destinations

The routers need to send broadcast for certain features to activate their functioning


Frame Relay Service Internetworking Frame Relay networks use Asynchronous Transfer

Mode (ATM) in the core of the Frame Relay network The working of ATM is similar to a Frame Relay.

However, ATM has certain features that make it more effective than Frame Relay

The service provider uses the ATM to build the core of the Frame Relay networks as shown in figure


Frame Relay Network


Network as it Appears to Routers


Configuration Steps for Remote Router routes


Steps to Change DLCI Status


Frame Configuration Command - I

Commands Description

encapsulation frame-relay [ieft|cisco]

Defines the Frame Relay encapsulation which is preferred over HDLC and PPP

frame-relay lmi-type{ansi|q933a|cisco]

Defines the type of LMI messages that are sent to the switch

bandwidth num Enables to set the interface speed of the router

frame-relay map [protocol protocol-address dlci}payload-compression frf9 stac caim [element-number][broadcast] [ieft|cisco]

Defines statically the mapping between the network layer and DLCI


Frame Configuration Command - IIkeepalive sec Enables to configure the way and time

interval that the LMI messages are sent and received

interface serial number.sub [point-to-point|multipoint]

Enables to create a subinterface or reference a subinterface that is already created

frame-relay interface-dlci dlci [ieft|cisco] [voice-cir cir] [ppp virtual-template-name]

Links the DLCI to the subinterface


Frame Configuration Commands in the Privileged Mode - I Command Description

show interfaces Displays the status of the physical interface

show frame-relay lmi [type number]

Displays LMI status information

show frame-relay pvc Displays a list of all the configured PVCs and DLCI numbers

show frame-relay map Provides a list of network layer addresses mapped to DLCI numbers

show ip route Displays the available routes for the packets to travel from one router to another


Basic Frame Relay Network


Verification of Frame Relay Encapsulation on Router1


Output of show ip route Command


Output of show frame-relay lmi Command


Output of show frame-relay pvc Command


Output of show frame-relay map Command


Configuring Frame Relay Subinterfaces Frame Relay subinterfaces provide a solution to the

problem of split horizon on the partially meshed Frame Relay networks

Cisco routers support two types of subinterfaces given as follows: Point-to-point subinterface Multipoint subinterfaces


Frame Relay Point-to-Point Subinterfaces


Frame Relay Multipoint Subinterfaces


Hub-and-Spoke Frame Relay Network


Fully Meshed Network


Frame Relay Congestion Control Frame Relay reduces the network overhead by

implementing congestion-control mechanism Frame Relay implements two congestion-notification

mechanisms such as Forward-explicit congestion notification (FECN) and Backward-explicit congestion notification (BECN)

The Frame Relay frame includes following three bits that allow congestion control: Discard Eligibility (DE) Forward-explicit congestion notification (FECN) Backward-explicit congestion notification (BECN)


Frame Relay Error Checking

Frame Relay uses cyclic redundancy check (CRC) error checking mechanism

The CRC compares two derived values from the two mathematical functions computed at the source and the destination devices

This determines whether an error occurred during the transmission of data from source to destination


Case Study

At the Gujarat branch of the Blue Diamond Steel organization, all Cisco routers are implemented on the network. The routers use HDLC as the default encapsulation method for data transmission. All the transaction between the departments of the company is carried out over the network. However, unfortunately, some important information of Finance department regarding policies could not reach to the Software Management department’s destination computer because it was lost in transit.


Problem

Information was lost due to network congestion in network


Suggested Solution

All the branches should be integrated using the Frame Relay technology. Frame Relay provides a

congestion control mechanism that can prevent the loss of critical data


Frame Relay Backup using ISDN


Output of show ip route Command


Troubleshooting Frame Relay

The commons issues in the Frame Relay can be resolved using the debug command

This command enables you to troubleshoot the Frame Relay connections

You can use the router console to enter these commands: debug frame-relay events Command debug Frame Relay packet Command


Summary - I

Frame Relay networks are multi-access networks where more than two devices can be attached to the network

A Virtual circuit (VC) represents the path on which the frame travels. Virtual circuits enable you to compare Frame Relay to leased physical circuit. There two types of virtual circuits are: Permanent virtual circuit (PVC) Switched virtual circuit (SVC)

LMI is the definition used between the Frame Relay DTE and Frame Relay DCE, which means that the data send by the DTE is processed between them


Summary - II

Sometimes you might face problems with the connection to the carrier switch. The commands available are to troubleshoot LMI are: show interfaces show frame-relay lmi debug frame-relay lmi

The DLCI identifies a virtual circuit for the Frame Relay to forward the frames to appropriate remote site when multiple access list use the same access list


Summary - III

The Frame Relay implementation of Cisco provides with three different options to assign subnets and IP address on the Frame Relay interfaces. The options are: A subnet that contains all the Frame Relay data

terminal equipments (DTE) A subnet for each virtual circuit Hybrid of the above two

Frame Relay networks use Asynchronous Transfer Mode (ATM) in the core of the Frame Relay network

ccna chapter 11 by jetarvind kumar madhukar

Education

frame relay components

encapsulation frame

time frame relay

limitation of frame

frame layer

frame format

functionality of frame

frame travels