Differentiate between the following WAN services: FRAME RELAY, ISDN/LAPD, HDLC and PPP
Frame relay is used to connect large number of sites in the network because it is relatively inexpensive to do so. The service provider gives you a frame relay circuit and is charged for the amount of data and the bandwidth you use as oppose to T1 circuit that charges with a flat monthly rate whether you use partial bandwidth or the full bandwidth regardless. Frame relay is a high performance WAN protocol that operates at the Data Link layer and the Physical layer of the OSI model.
Integrated Services Digital Network (ISDN) is designed to run over existing telephone networks. It can deliver end to end digital service carrying voice and data. ISDN operates at OSI model, physical layer, data link layer and network layer. It can carry multimedia and graphics with all other voice, data services. ISDN supports all upper layer protocolsand you can choose PPP, HDLC or LAPD as your encapsulation protocol. It has two offerings, Primary rate which is 23B+D channels. 23, 64 kbps and one 64kbps mainly used for signaling. The other is the Basic Rate which has 2B+D channels two 64kbps and one 16kbps.
At data link layer ISDN supports two protocols; LAPB and LAPD. LAPB is used to mainly transfer data from upper layers and has three types of frames. I-Frames carry upper layer information and carries out sequencing, flow control, error detection and recovery. S- Frames carry control information for the I-frame. LAPD provides an additional multiplexing function to the upper layers enabling number of network entities to operate over a single physical access. Each individual link procedure acts independently of others. The multiplex procedure combines and distributes the data link channels according to the address information of the frame. Each link is associated with a specific Service Access Point (SAP), which is identified in the part of the address field.
High Level Data Link Control (HDLC) is a bit oriented data link layer frame protocol that has many versions similar to LAP, LAPB, and LAPD. CISCO routers default encapsulation is HDLC, but it is proprietary to CISCO.
Point to Point Protocol (PPP) is a Data Link Layer protocol that can be used over ether asynchronous (dial up) or synchronous (ISDN) lines. It uses Link Control Protocol (LCP) to build and maintain data link connections. Included in PPP is the authentication protocols, PAP and CHAP, and data compression. It supports IP, IPX, AppleTalk, DECnet and OSI/CLNS.
Recognize key Frame Relay terms and features
Frame Relay is a high performance WAN protocol that operates at the physical and data link layer of the OSI reference model. It was originally designed to operate on ISDN circuits, but today it is used on variety of network interfaces. To configure Frame Relay on a CISCO router, we have to specify it as an encapsulation on a serial interface. There are only two encapsulation methods are available, CISCO, the default and the type IETF.
A frame Relay connection between CISCO devices the type: CISCO is used and between a CISCO device and a non CISCO device type IETF is used.
#encapsulation frame relay cisco or #encapsulation frame relay ietf
Frame Relay virtual circuits are identified by Data Link Connection Identifiers (DLCI). DLCIs are issued by the Frame Relay service provider. It is used to map IP addresses at each end of the virtual circuit. Local Management Interface (LMI) was developed by CISCO and others to enhance the CCITT-ITU standard with protocol features that allowed internetworking devices communicate easily with a Frame Relay network. LMI messages provide current DLCI values, global or local significance of the DLCI values and the status of virtual circuits. CISCO supports three types of LMIs: CISCO which is the default, ANSI and Q933A.
List commands to configure, maps and subinterfaces
To configure DLCI (config-if) #frame-relay interface-dlci 16 Any number from 0 to 4292967295 can be as the DLCI number.
To configure LMI (config-if)#frame-relay lim-type q933a
Subinterfaces can have multiple virtual circuits on a single serial interface and treat each virtual circuit as a separate interface. The advantage of using subinterfaces is that you can assign different network layer characteristics each subinterface and virtual circuit, such as IP routing on one virtual circuit and IPX routing on another.
(config)# int s0.16 The serial interface s0 configured with a subinterface 16
There are two types of subinterfaces, point to point and multipoint. Point to point is used when a single virtual circuit connect one router to another. Multipoint is used when the router is in the middle of star virtual circuits.
Map command is used to map IP devices address at the end of the virtual circuits to DLCIs so that they can communicate. There are two types of mapping: Use Frame Relay map command and use inverse-arp function. Example of Frame Relay map command:
#int s).16
#encap frame relay ietf
#no inverse-arp
#ip address 172.16.30.1 255.255.255.0
#frame relay map ip 172.16.30.17 30 cisco broadcast
Example of Frame Relay inverse-arp command:
#int s0.16
#encap frame-relay ietf
#ip address 172.16.30.1 255.255.255.0
Frame relay is used to connect large number of sites in the network because it is relatively inexpensive to do so. The service provider gives you a frame relay circuit and is charged for the amount of data and the bandwidth you use as oppose to T1 circuit that charges with a flat monthly rate whether you use partial bandwidth or the full bandwidth regardless. Frame relay is a high performance WAN protocol that operates at the Data Link layer and the Physical layer of the OSI model.
Integrated Services Digital Network (ISDN) is designed to run over existing telephone networks. It can deliver end to end digital service carrying voice and data. ISDN operates at OSI model, physical layer, data link layer and network layer. It can carry multimedia and graphics with all other voice, data services. ISDN supports all upper layer protocolsand you can choose PPP, HDLC or LAPD as your encapsulation protocol. It has two offerings, Primary rate which is 23B+D channels. 23, 64 kbps and one 64kbps mainly used for signaling. The other is the Basic Rate which has 2B+D channels two 64kbps and one 16kbps.
At data link layer ISDN supports two protocols; LAPB and LAPD. LAPB is used to mainly transfer data from upper layers and has three types of frames. I-Frames carry upper layer information and carries out sequencing, flow control, error detection and recovery. S- Frames carry control information for the I-frame. LAPD provides an additional multiplexing function to the upper layers enabling number of network entities to operate over a single physical access. Each individual link procedure acts independently of others. The multiplex procedure combines and distributes the data link channels according to the address information of the frame. Each link is associated with a specific Service Access Point (SAP), which is identified in the part of the address field.
High Level Data Link Control (HDLC) is a bit oriented data link layer frame protocol that has many versions similar to LAP, LAPB, and LAPD. CISCO routers default encapsulation is HDLC, but it is proprietary to CISCO.
Point to Point Protocol (PPP) is a Data Link Layer protocol that can be used over ether asynchronous (dial up) or synchronous (ISDN) lines. It uses Link Control Protocol (LCP) to build and maintain data link connections. Included in PPP is the authentication protocols, PAP and CHAP, and data compression. It supports IP, IPX, AppleTalk, DECnet and OSI/CLNS.
Recognize key Frame Relay terms and features
Frame Relay is a high performance WAN protocol that operates at the physical and data link layer of the OSI reference model. It was originally designed to operate on ISDN circuits, but today it is used on variety of network interfaces. To configure Frame Relay on a CISCO router, we have to specify it as an encapsulation on a serial interface. There are only two encapsulation methods are available, CISCO, the default and the type IETF.
A frame Relay connection between CISCO devices the type: CISCO is used and between a CISCO device and a non CISCO device type IETF is used.
#encapsulation frame relay cisco or #encapsulation frame relay ietf
Frame Relay virtual circuits are identified by Data Link Connection Identifiers (DLCI). DLCIs are issued by the Frame Relay service provider. It is used to map IP addresses at each end of the virtual circuit. Local Management Interface (LMI) was developed by CISCO and others to enhance the CCITT-ITU standard with protocol features that allowed internetworking devices communicate easily with a Frame Relay network. LMI messages provide current DLCI values, global or local significance of the DLCI values and the status of virtual circuits. CISCO supports three types of LMIs: CISCO which is the default, ANSI and Q933A.
List commands to configure, maps and subinterfaces
To configure DLCI (config-if) #frame-relay interface-dlci 16 Any number from 0 to 4292967295 can be as the DLCI number.
To configure LMI (config-if)#frame-relay lim-type q933a
Subinterfaces can have multiple virtual circuits on a single serial interface and treat each virtual circuit as a separate interface. The advantage of using subinterfaces is that you can assign different network layer characteristics each subinterface and virtual circuit, such as IP routing on one virtual circuit and IPX routing on another.
(config)# int s0.16 The serial interface s0 configured with a subinterface 16
There are two types of subinterfaces, point to point and multipoint. Point to point is used when a single virtual circuit connect one router to another. Multipoint is used when the router is in the middle of star virtual circuits.
Map command is used to map IP devices address at the end of the virtual circuits to DLCIs so that they can communicate. There are two types of mapping: Use Frame Relay map command and use inverse-arp function. Example of Frame Relay map command:
#int s).16
#encap frame relay ietf
#no inverse-arp
#ip address 172.16.30.1 255.255.255.0
#frame relay map ip 172.16.30.17 30 cisco broadcast
Example of Frame Relay inverse-arp command:
#int s0.16
#encap frame-relay ietf
#ip address 172.16.30.1 255.255.255.0
List commands to monitor Frame Relay operation on the router
In the user mode key in the following:
Router>sho frame ?
ip show frame relay IP statics
lmi show frame relay lmi statics
map show frame relay map table
pvc show frame relay pvc statics
route show frame relay route
traffic show frame relay protocol statics
Identify PPP operations to encapsulate WAN data on CISCO routers
Point to Point Protocol (PPP) is a data link protocol that can be used on asynchronous (dial up) or synchronous ISDN circuits. It uses Link Control Protocol (LCP) to build and maintain data link connections. Some features included in PPP are: Password Authentication Protocol (PAP) and Challenge Handshake Password Authentication Protocol (CHAP). Data compression and multiprotocols such as IP, IPX , AppleTalk DECnet and OSI/CLNS are supported. Encapsulate PPP on the router
#int s0#encapsulate ppp
State a relevant use and context for ISDN networking
Integrated Services Digital Network (ISDN) can run on existing telephones lines to provide an end to end digital service for both domestic and business uses. ISDN can carry, in addition to voice and data, multimedia as well. ISDN can used as a backup circuit for high speed network links. CISCO routers can be configured to automatically dial up on an ISDN link when the main network link goes down.
Identify ISDN protocols, function groups, reference points and channels
ISDN protocols were defined by CCITT (now ITU-T), and there are three protocols that define the complex transmission issues:
· Protocol specifications beginning with latter E, specify ISDN on the existing
telephone network, ie; Analog lines.
· Protocol specifications beginning with letter I, specify concepts, terminology
and services.
· Protocol specifications beginning with letter Q, specify trunk switching and
signaling.
Describe CISCO’s Implementation of ISDN BRI
ISDN Basic Rate Interface (BRI), service provides two B channels and D channel, which is also known as 2B+D. B channels operate at 64 kbps and carries user information where D channel operates at 16 kbps and usually carry control and signaling information. D channel signaling protocol spans the OSI reference model’s, Physical layer, Data link layer and the Network layer. The two 64 kbps lines can be used as a single 128 kbps channel. To place a call on ISDN is similar to placing a call on Plain Old Telephones (POTS). For ISDN network to identify a call placed on its network, you must use directory numbers and Service Profile Identifiers (SPID)s. These two items are given to you by the service provider. Directory number is a telephone number you will use when you call. The SPID is a number the telephone uses to identify equipment on your ISDN
connection. Majority of switches in US are either AT&T 5ESS, 4ESS or Northern Telcom DMS 100. Attaching a CISCO router to ISDN needs either a Network Termination 1 or an ISDN modem. If router has a BRI interface, (called Terminal End Point 1) then it is ready to be connected to the ISDN network.
Router#config t
Router(config)#isdn switch-type basic-dms100
Router(config)#int bri0
Router(config-if)#encap ppp
Router(config-if)#isdn spid 775456721
Router(config-if)#ppp authentication chap
Identify ISDN protocols, function groups, reference points and channels
ISDN protocols were defined by CCITT (now ITU-T), and there are three protocols that define the complex transmission issues:
· Protocol specifications beginning with latter E, specify ISDN on the existing
telephone network, ie; Analog lines.
· Protocol specifications beginning with letter I, specify concepts, terminology
and services.
· Protocol specifications beginning with letter Q, specify trunk switching and
signaling.
Describe CISCO’s Implementation of ISDN BRI
ISDN Basic Rate Interface (BRI), service provides two B channels and D channel, which is also known as 2B+D. B channels operate at 64 kbps and carries user information where D channel operates at 16 kbps and usually carry control and signaling information. D channel signaling protocol spans the OSI reference model’s, Physical layer, Data link layer and the Network layer. The two 64 kbps lines can be used as a single 128 kbps channel. To place a call on ISDN is similar to placing a call on Plain Old Telephones (POTS). For ISDN network to identify a call placed on its network, you must use directory numbers and Service Profile Identifiers (SPID)s. These two items are given to you by the service provider. Directory number is a telephone number you will use when you call. The SPID is a number the telephone uses to identify equipment on your ISDN
connection. Majority of switches in US are either AT&T 5ESS, 4ESS or Northern Telcom DMS 100. Attaching a CISCO router to ISDN needs either a Network Termination 1 or an ISDN modem. If router has a BRI interface, (called Terminal End Point 1) then it is ready to be connected to the ISDN network.
Router#config t
Router(config)#isdn switch-type basic-dms100
Router(config)#int bri0
Router(config-if)#encap ppp
Router(config-if)#isdn spid 775456721
Router(config-if)#ppp authentication chap
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