Thanx for bruising my brain Diffy Phil.
--- Diffy De Villiers wrote: > Just to add on to what Hal said: > > The terms DTE/DCE are used at both layer1 and layer2 > of the OSI model > and at both layers they represent different > entities. > > A layer1 DTE is an acronym for a physical Data > Terminal Equipment (i.e. > a device which physically controls interface signals > such as DTR, RTS > and TxD on a serial interface). > > A layer1 DCE is an acronym for Data Communications > Equipment (i.e. a > device which controls interface signals such as DSR, > CTS, DCD and RxD > and signal timing). > > A layer2 DTE is an acronym for a logical (not > physical) Data Terminal > Equipment (i.e. a device which generate frames in > the format of a DTE > device as laid out in the protocol specification - > for example a LAPB > DTE always generates commands with an address-field > value of 1). From a > WAN service provider's point of view, the DTE > devices are normally the > equipment connected to the modem at the customer's > premises (normally > the router's serial interface). > > A layer2 DCE is an acronym for a logical Data > Circuit-terminating > Equipment (i.e. a device which generate frames in > the format of a DCE > device as laid out in the protocol specification - > for example a LAPB > DCE always generates commands with an address-field > value of 1). From a > WAN service provider's point of view, the DCE > devices are normally the > WAN switches at its premises. > > To now really confuse things, picture the following > serial link: > - Router at Customer Premises connected to a Modem > - Modem at Customer Premises connected to Modem at > Service Provider. > - Modem at Service Provider connected to WAN Switch. > > At layer 1, the router and WAN switch are known as > DTEs, the two modems > are the DCEs. > > At layer 2, the router is a DTE and the WAN switch > is a DCE (see above > definitions). In other words the WAN switch is both > a DTE (layer 1) and > a DCE (layer 2). And who said networking is easy > :-). > > NOTE that the term DTE refers to Data Terminal > Equipment at both layer1 > and layer2, but the term DCE represents different > acronyms at layers 1 > and 2. > > I hope this adds some light to the confusion!!! > > Kind Regards > > Diffy > > >>> "Phil Barker" 01/23/02 05:29PM >>> > Thanks for your answer Hal, > > I'm back on track now. > > Regards, > > Phil. > > --- "Logan, Harold" wrote: > > Phil, > > > > You and your students are falling into a trap > that's > > caused confusion > > for a lot of people, especially netacad students. > > Your student is > > correct though; normally all devices on the LAN > side > > are DTE equipment. > > The terms DTE and DCE only apply on the WAN side > of > > things... if you try > > to apply that terminology on the LAN side, you're > > bound to confuse > > yourself. Add to that, the netacad curriculum only > > tells you the > > definition of DCE and DTE equipment; it doesn't > tell > > you how the > > terminology gets applied. I personally don't like > > the fact that semester > > 2 tests students on their knowledge of WAN > > topologies and terminologies, > > when that material is really covered in semester > > 4... but that's a > > different soap box. > > > > The traditional workgroup LAN switch doesn't > really > > have a place in the > > WAN scheme of things. I know the curriculum will > > occasionally reference > > switches and DCE in the same sentence; in every > case > > I've seen so far, > > they're actually referring to WAN switches, not > LAN > > switches. There are > > probably several readers on the list who are > reading > > this and cringing, > > and thinking of any number of LAN switches that > also > > connect to a WAN > > service, but that's a bit beyond the CCNA level of > > understanding... it's > > definitely beyond the NetAcad semester 2 level. > Here > > you're sometimes > > better off omitting data for now and applying the > > KISS principle. LAN > > switches are DTE equipment, but they don't play an > > important role on the > > WAN side. > > > > As for connecting routers, hubs, switches, and > > workstations, I know it's > > tempting to call routers and computers DTE and to > > call switches and hubs > > DCE. That misnomer will work for you 9 times out > of > > 10, but it's > > fundamentally incorrect. Applying the KISS > principle > > again, you can just > > say "Like devices need a crossover cable, and > unlike > > devices need a > > patch cable". If you want to explain it a little > bit > > further, you may > > want to point out the X's on the port numbers of > one > > of your Cat 1900 > > switches. Also, many (but not all) hubs do the > same > > thing, and they use > > two parallel lines to indicate an uplink port. The > X > > indicates that a > > cross happens internally to the switch, so that > one > > device's Send is > > talking to the other device's Receive. If you go > > directly from a PC to a > > router, you don't have that cross working for you, > > so you need to use a > > crossover cable. > > > > Hopefully that dispelled more confusion than it > > caused. Good luck with > > the class, > > > > Hal Logan CCAI, CCDP, CCNP+Voice > > Network Specialist / Adjunct Faculty > > Computing and Engineering Technology > > Manatee Community College > > > > > > > -----Original Message----- > > > From: Phil Barker > > [mailto:[EMAIL PROTECTED]] > > > Sent: Wednesday, January 23, 2002 7:47 AM > > > To: [EMAIL PROTECTED] > > > Subject: DTE/DCE definitions ? CCAI woes. > > [7:32924] > > > > > > > > > Hi group, > > > > > > I have just started teaching as a CCAI and was > > asked > > > the following question yesterday in class. > > > > > > One student pointed out that the Sem 2 > curriculum > === message truncated === __________________________________________________ Do You Yahoo!? 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