1,ISDN specifies a number of reference points that define logical interfaces between functional groups, such as TAs and NT1s. ISDN reference points include the following:
R:The reference point between non-ISDN equipment and a TA
S:The reference point between user terminals and the NT2
T:The reference point between NT1 and NT2 devices
U:The reference point between NT1 devices and line-termination equipment in the carrier network. The U reference point is relevant only in North America, where the NT1 function is not provided by the carrier network
2,According to Cisco:Two layer 3 specifications are used for ISDN signaling:ITU-T I.450 (also known as ITU-T Q.930) and ITU-T I.451(also known as ITU-T Q.931). Together, these protocols
support user-to-user, circuit-switched, and packet-switched connections. A variety of call-establishment, call-termination, information and miscellaneous messages are specified, including SETUP, CONNECT, RELEASE, USER INFORMATION, CANCEL, STATUS, and DISCONNECT. These messages are functionally similar to those provided by the X.25 protocol
3,Layer 2 of the ISDN signaling protocol is Link Access Procedure, D channel(LAPD). LAPD is similar to High-Level Data Link Control(HDLC) and Link Access Procedure, Balanced(LAPB). As the expansion of the LAPD acronym indicates, this layer it is used across the D channel to ensure that control and signaling information flows and is received properly
4,At the TestKing network, you are responsible for provisioning and setting up new ISDN connections. A new ISDN PRI is being installed at a remote location and you want to configure the router. What T1 controller command can you use to configure the controller for ISDN PRI operation?
answer:ISDN switch-type
5,If a frame handler suffers from congestion, it will notify the corresponding access nodes by FECN(C/R=0) and BECN(C/R=1) bits set to one. The access nodes won't accept frames that exceed the CIR any longer unless the congestion alarm has stopped(FECN=0, BECN=0)
When the congestion queue thresholds configured at the interface or class level of the PE router are exceeded, PE router does the following:
Sets the FECN bit to 1 on the outgoing packets
Sets the BECN bit to 1 for all traffic destined for the originating CE router, which decreases its traffic based on the number of BECN packets it received
6,Show frame-relay pvc
The show frame-relay pvc command displays the status of each configured connection as well as traffic statistics. This command is also useful for viewing the number of backward explicit
congestion notification(BECN) and forward explicit congestion notification(FECN) packets received by the router. the PVC status can be active,inactive, or deleted.
7,LMI(Local Management Interface)
Local Management Interface (LMI) is a signaling standard between the CPE device and theFrame Relay switch that is responsible for managing the connection and maintaining status between the devices. LMIs include support for a keepalive mechanism, which verifies that
data is flowing; a multicast mechanism, which provides the network server with its local DLCI; the multicast addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a status mechanism, which provides an ongoing status on the DLCIs known to the switch.
Although the LMI is configurable, beginning in Release 11.2, the Cisco router tries to autosense which LMI type the Frame Relay switch is using by sending one or more full status requests to the Frame Relay switch. The Frame Relay switch responds with one or
more LMI types. The router configures itself with the last LMI type received. Three types of LMIs are supported:
• cisco - LMI type defined jointly by Cisco, StrataCom, Northern Telecom, and Digital
Equipment Corporation, nicknamed “the gang of four”
• ansi - Annex D, defined by the ANSI standard T1.617
• q933a - ITU-T Q.933 Annex A
8,CIR(committed information rate)
The CIR is the rate that an administrator would want to transmit at during times when the network isn't congested. The CIR that you want isn't necessarily the same as the CIR of the service provider.CIR rates are purchased from the provider. When the data rates exceed the CIR, the frames are marked as Discard Eligible(DE) and are not guaranteed to be delivered across the frame relay network
9,SVCs(switched virtual circuits)
SVCs are temporary connections used in situations requiring only sporadic data transfer between DTE devices across the Frame Relay network. A communication session across an SVC consists of the following four operational states:
Call setup,Data transfer,Idle,Call termination
10,Which statement best describes a digital certificate, which is being implemented in the TestKing network as a VPN technology?
answer:A digital identification mechanism which establishes credentials issued by a certification authority
Digital certificates,on the other hand, use a trusted third-party authentication system, which scales linearly when the number of involved parties becomes large. A CA(certification authority) is an entity trusted by all the certificate users or that has been granted power to issue digital certificates and vouch for the binding between data items contained in a certificate.The CA manages the life cycle of certificates and, depending on the type of certificate and the certification practice statement that applies, may be responsible for the life cycle of key paris associated with the certificates.
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