Thank you Denys. Nice to see someone reverting to basics. I assume that
the 7 layer model is still current?
In my search through the IT vacancies I have come across several adds
for Applications Programmers with a knowledge of TCP/IP. Why? At the AP
level I would expect this layer to be all but invisible.
What am I missing?
Regards
John
--- Denys Beauchemin <[log in to unmask]> wrote:
> X-no-Archive:yes
> 10BASE-T is an implementation of the Ethernet IEEE
> standard on 24 gauge
> unshielded twisted-pair wiring, a baseband medium,
> at 10 megabits per second.
>
> Ethernet is a 10 megabits per second baseband.
> CSMA/CD network originally
> designed by Xerox corporation. It is now available
> at 100 Mbps on 100BASE-Tx
> and coming shortly, Gigabit Ethernet.
>
> Baseband is a network in which the entire bandwidth
> of the transmission medium
> is used by a single digital signal. Unlike
> broadband, no modulation techniques
> are used.
>
> Now, let us go back to the OSI model which was
> defined as 7 layers.
>
> 1- Physical layer. The first, or physical layer, of
> the OSI model conveys the
> bits that move along the cable. It is responsible
> for making sure that the raw
> bits get from one place to another, no matter what
> shape they are in. It deals
> with the mechanical and electrical characteristics
> of the cable. (Examples:
> Ethernet (10BASE-2, 10BASE-T, 100BASE-Tx), FDDI,
> Token ring)
> 2- Data-Link layer. The second, or data-link, layer
> of the OSI model is
> responsible for getting data packaged and onto the
> network cable. It manages
> the physical transfer, providing the blocks of data,
> synchronization, error
> control and flow control. The data-link layer is
> often subdivided into two
> parts - Logical Link Control (LLC) and Medium Access
> Control (MAC) - depending
> on the implementation. (Examples LLC, Ethernet,
> HDLC, MAC)
> 3- Network Layer. The third layer establishes,
> maintains and terminates
> connections. The network layer is responsible for
> translating logical
> addresses, or name, into physical addresses.
> (Examples: IP, APPC, X.25)
> 4- Transport Layer. The fourth layer ensures data is
> sent successfully between
> the two computers. If data is sent incorrectly,
> this layer has the
> responsibility to ask for retransmission of the
> data. (Examples: TCP, NetBEUI)
> 5- Session Layer. The session layer decides when to
> turn communication on and
> off between two computers. It coordinates the
> interaction between them,
> Unlike the network layer, it deals with the
> programs running in each machine
> to establish conversations between them. (Examples:
> UDP, NetBIOS)
> 6- Presentation Layer. The sixth or presentation
> layer performs code
> conversion and data reformatting. It is the
> translator of the network, making
> sure the computer is talking in the right language
> for the network.
> 7- Application Layer. The final layer is the
> interface between the software
> running in the computer and the network. It
> supplies functions to the software
> in the computer, such as electronic mail or file
> transfer. (Examples: SMTP,
> FTP, NFS, Telnet, SNMP, FTAM X.400, JTAM X.500)
>
> Hope this helps clear the air, so to speak.
>
> Kind regards,
>
> Denys. . .
>
> Denys Beauchemin
> HICOMP
> (800) 323-8863 (281) 288-7438 Fax: (281)
> 355-6879
> denys at hicomp.com
> www.hicomp.com
>
>
> -----Original Message-----
> From: Newman, Kevin: [SMTP:[log in to unmask]]
> Sent: Thursday, 08 July, 1999 1:13 PM
> To: [log in to unmask]
> Subject: Re: can you make terminals work on a
> network?
>
> So, if 10baseT is a protocol, where are the specs
> for it?
>
> I thought that it stood for 10Mbps capable wire,
> connector, or NIC. My
> 10baseT NIC is not tied to a specific protocol. I
> can run IPX, IP, or
> anything else that I can program to run on it. The
> NIC is about as low
> level as you can get - hardware, yet it is a 10baseT
> card.
>
> So where is the line drawn between protocol and
> hardware?
>
> Kevin
>
> > -----Original Message-----
> > From: Rick Clark [SMTP:[log in to unmask]]
> > Sent: Thursday, July 08, 1999 10:54 AM
> > To: [log in to unmask]
> > Subject: Re: can you make terminals work on a
> network?
> >
> > 10baseT is a protocol. What we should have been
> saying is, as someone
> > pointed out earlier, that the cable infrastructure
> is CAT5 (or CAT3
> > depending on your requirements).
> >
> > Rick Clark
> > WW&R
> >
> >
> > "Johnson, Tracy" wrote:
> > >
> > > THAT I can understand, copper is copper and
> crimping it down to
> > whatever contact on an RJ-45 is not a problem,
> I've been doing that
> > for years. I think of 10BaseT as a protocol, not
> a cable type.
> > >
> > > So back to my original thought, how does he get
> serial RS-232 to
> > talk 10BaseT protocol? Or is this not the
> question? The only valid
> > recipient for RS-232 protocol at one end is RS-232
> at the other.
> > >
> > > If the reference is only to cable, no problem, a
> no-brainer, I've
> > used bent paper clips on some interfaces.
> > >
> > > So, is 10BaseT a protocol or a cable?
> > >
> > > -----Original Message-----
> > > From: Bryan Greenberg
> [SMTP:[log in to unmask]]
> > > Sent: Thursday, July 08, 1999 10:10 AM
> > > To: [log in to unmask]
> > > Subject: Re: can you make terminals work
> on a network?
> > >
> > > Tracy Johnson poses the question:
> > > I'm at a loss to understand how Bryan does it.
> Especially a
> > terminal
> > > model that has only a serial port connected
> directly to a 10baseT
> > port
> > > in the second sentence.
> > >
> > > I may have munged up my thoughts on this one.
> Basically you
> > leverage
> > > the existing (or in this case newly installed)
> network wiring by
> > > running your serial terminals over the 10baseT
> cable. Most
> > > installations of network wiring will have RJ-45
> jacks on the node
> > end
> > > that are connected by individual runs of cat5
> cable to some sort of
> > > punch down panel. Normally you would then run a
> patch cable from
> > the
> > > punch down panel to a hub, completing the
> connection. If you run
> > that
> > > patch cable to a dtc instead you get a serial
> connection (if you've
> > > plugged a terminal in on the other end). If
> your network is more
> > > exotic (ie switched or not on the same side of a
> router as the dtc)
> > > then this configuration will not work.
> > >
> > > I hope this clears the fog from my writing.
> > >
> > > Bryan
>
=== message truncated ===
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