Dce Dte
Cisco Ccna And Ccnp Bcran Exam Training Frame Relay Pvc, Svc, Dlci, And Map Statements
Cisco CCNA And CCNP BCRAN Exam Training Frame Relay PVC, SVC, DLCI, and Map Statements
In today's CCNP certification tutorial, we'll concentrate on the BCRAN exam and Frame Relay PVCs, SVC, and DLCIs in particular.Visit here http://plumbingsupply-copperorg.blogspot.com
There are actually two kinds of virtual circuits - Permanent Virtual Circuits (PVCs) and Switched Virtual Circuits (SVCs). An SVC doesn't have anything to do with an L2 switch - it's a VC that is built only under predefined circumstances, similar to an ISDN connection that is only built when interesting traffic hits the line. SVCs go through a basic four-step process, and it's a lot like ISDN:
Call Setup -- Just what it sounds like, the circuit between the two DTEs is created.
Data Transfer -- Again, just what it sounds like.
Idle -- The connection is active, but no data is going across the line. As with an ISDN call, if the call stays idle too long, the call will be torn down.
Call Termination - The call is torn down.
A PVC is just what the name says - it's permanent, and is already built when traffic needs to be sent. PVCs have two steps, data transfer and idle. Unlike an SVC, when a PVC goes to idle, the PVC will not be torn down.
The DLCI (pronounced "del-see") is simply an identifier for the connection between the DTE and the closest DCE in the frame switch. If Spoke1 is going to use the path shown below to communicate with the hub, the DTE defines the connection between Spoke1 and the first Frame switch in the cloud. You don't just make the DLCI number up - the Frame provider will provide you with the DLCIs you should use.
The key to a successful Frame configuration is remembering that the local DLCI must be mapped to a remote IP address. There are two ways to do this, one being dynamic and the other involving a static configuration. Those of you who have read my previous books know that I'm all for the router and the switch using dynamic methods as often as possible, since dynamically learned information is the easiest information to keep current. However, in this case, the static method of DLCI - IP address mapping is considered more reliable than the dynamic method, Inverse Address Resolution Protocol (IARP).
To allow IARP to perform dynamic mappings, just enable Frame with encapsulation frame-relay and open the interface. When you see the word dynamic in the output of show frame map, that particular mapping was performed by Inverse ARP.
It's highly recommended that you run either static or dynamic DLCI mappings - don't use them both on the same interface. This can result in incomplete mappings if and when the router is reloaded.Visit here http://plumbingsupply-copperorg.blogspot.com
About the Author
Visit here http://plumbingsupply-copperorg.blogspot.com
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Differences Between RS232, RS485 And RS422
RS232, RS485 and RS422 mainly defines the electrical signal characteristics of drivers and receivers like, signaling rate, voltage levels, short circuit behavior, maximum load capacity and voltage withstand levels. But there are some differences between each of them. Any engineer or specialist in electronic data communications can differentiate between RS232, RS485 and RS422 easily but it might not be easy for all. For them, the differences between the three are enlisted below.
1. RS232 is the oldest standard of the Electronics Industries Associations (EIA) which was followed later by RS422 and RS485. The origin of RS232 can be traced back to the days when remote teletype machines were connected to main frames via modems. Communications between DCE (Data Circuit-terminating equipment) and DTE (Data Terminal Equipment) used to happen sequentially. The entire process was very slow and very mechanical. With the help of RS232, EIA made a standard which minimized incompatibilities to make life easier for those involved with the information technology department and data communication. But shortcomings and limitations in speed, flow control and reliability posed a question on the performance of RS232. This is where RS422 came in. RS422 provided a solution to the problem by using two sets of negative and positive pairs of voltages. RS422 has speed up to 10 megabits per second with a connection distance of about 4000 feet.
2. RS422 has two twisted pairs carrying negative and positive voltages which help it to communicate in both directions at the same time. In case of RS232, communication takes place one after another. RS422 provides data transmission using differential or balanced signaling. It has unidirectional and non reversible transmission lines. Unlike EIA 485, it allows multiple receivers but not multiple drivers. It has the advantage of differential receiver, differential driver and high data rates (10 megabaud at 12 meters). EIA 422 on the other hand only specifies the characteristics of electrical signaling of a single balanced signal.
RS485 also uses twisted pairs of negative and positive voltage differentials but for serial binary data communication. This is also known as EIA-485, TIA 485 because this was published by the ANSI Telecommunication Industry Association (TIA) and Electronic Industries Alliance (EIA). They can be effectively used over long distances and in environments with electrical noises. Multiple receivers can be connected to these in a multi-drop configuration.
3. RS232 and RS422 are point to point protocols but RS485 devices are addressable and have the capacity to communicate with multiple nodes, up to 32. However, RS 485 works almost like RS422 in matters of speed and distance.
4. RS485 is appropriate for variety of master or slave networks and architecture connections. Each of them can be connected bi-directionally as line termination requires special consideration. But as RS232 and RS422 are point to point, they are not suitable for this purpose.
5. As RS422 has a single driver circuit, it cannot be switched off, but EIA 485 or RS485 drivers are required to be put in the transmit mode by placing a signal to the driver.
These are the basic differences between RS232, RS422 and RS485 largely used in various industrial and commercial systems.
About the Author
Mordy Naftaly author of this article. RS232, RS422 and RS485 mainly define the electrical signal characteristics, of drivers and receivers. But still, they differ from each other and have individual characteristics and advantages.