Terms that drive me crazy

webistan

I admit I've tried to understand these terms over and over again, but I find them really confusing

-DCE/DTE
-CSU/DSU
-LAPB/LAPD

Can somebody care to clarify these.

TheShadow

Here is a general definition of the first four terms

DCE, which stands for data communications equipment or data circuit-terminating equipment, refers to a modem that is used in conjunction with a computer as the DTE (data terminal equipment).

More generally, a DCE is any device capable of communicating with the appropriate DTE, and of providing access to the appropriate type of line. For example, a modem can speak to a computer and can provide access to analog telephone lines. In digital telecommunications, a DSU (data service unit) and a CSU (communications service unit) together make up a DCE, and provide access to the digital lines.

Of course DCE/DTE cross over cables warp the whole definition of the physical boxes described above.

The last two are link access protocols in the data link layer. Here are some general definitions.

LAPB - (Link Access Protocol, Balanced) A bit-oriented, data-link layer protocol that is used in X.25 connections, such as to connect a terminal or node to a packet-switched network. LAPB is based on the HDLC protocol, and it can support half- or full-duplex communications in a point-to-point link. LAPB supports only the asynchronous balanced mode (ABM) of data transfer.

LAPD - (Link Access Protocol, D channel), which is used in ISDN (Integrated Services Digital Network). A D channel is a 16 or 64 kilobit channel used of signaling. Error correction follows that path while ISDN B channels handle data.


So whats bugging you about these or do the definitions solve it.

webistan

Thanks TheShadow, it's more clear now. I think sometimes it's better to learn material in 'human language' than staring at the book to make sense of something . Thanks again