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Home > Archive > alt.certification.network-plus > December 2002 > The next directly coonected device
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The next directly coonected device
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| anna c 2002-12-20, 8:24 pm |
| Hey guys. Sorry to be asking so many questions, but I am trying to
visualize some things. Here goes: Suppose you have 4 computers: A,
B, C, and D all connected to a switch in that order. B wants to send
data to D. As the data travels the OSI layers, it gets to the Data
Link layer. This layer adds the physical address (im assuming MAC
Address) of the next directly connected device. Which device is this
in the above scenario. I would assume the MAC Address of the switch,
but I dont know. What if these same 4 computers were configured in a
physical bus topology. Which PC is the next directly connected
device? Is it A or C? Which direction does the bits flow when it
leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
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| Slammer 2002-12-20, 8:24 pm |
| If you are using a Switch it will go directly to the destination, thus
reducing network traffic. This is why people setup switched networks.
--
Slammer
MCSA, CNA, NET+, A+
"anna c" <cwesthaven@hotmail.com> wrote in message
news:7e04dc8b.0212201732.54860376@posting.google.com...
> Hey guys. Sorry to be asking so many questions, but I am trying to
> visualize some things. Here goes: Suppose you have 4 computers: A,
> B, C, and D all connected to a switch in that order. B wants to send
> data to D. As the data travels the OSI layers, it gets to the Data
> Link layer. This layer adds the physical address (im assuming MAC
> Address) of the next directly connected device. Which device is this
> in the above scenario. I would assume the MAC Address of the switch,
> but I dont know. What if these same 4 computers were configured in a
> physical bus topology. Which PC is the next directly connected
> device? Is it A or C? Which direction does the bits flow when it
> leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
| |
| Howard Phillips 2002-12-20, 9:24 pm |
| The MAC address would the the destination MAC address, in this case the MAC
of computer D.
Your computer maintains a table that tracks IP and MAC addresses. When the
computer sends a packet it uses the NETMASK to determine if the computer is
local or remote. If its local the MAC used is the MAC of the destination
device. If its remote the MAC of the GATEWAY is used.
"anna c" <cwesthaven@hotmail.com> wrote in message
news:7e04dc8b.0212201732.54860376@posting.google.com...
> Hey guys. Sorry to be asking so many questions, but I am trying to
> visualize some things. Here goes: Suppose you have 4 computers: A,
> B, C, and D all connected to a switch in that order. B wants to send
> data to D. As the data travels the OSI layers, it gets to the Data
> Link layer. This layer adds the physical address (im assuming MAC
> Address) of the next directly connected device. Which device is this
> in the above scenario. I would assume the MAC Address of the switch,
> but I dont know. What if these same 4 computers were configured in a
> physical bus topology. Which PC is the next directly connected
> device? Is it A or C? Which direction does the bits flow when it
> leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
| |
| Paul Womar 2002-12-21, 5:24 am |
| anna c <cwesthaven@hotmail.com> wrote:
> Hey guys. Sorry to be asking so many questions, but I am trying to
> visualize some things. Here goes: Suppose you have 4 computers: A,
> B, C, and D all connected to a switch in that order. B wants to send
> data to D. As the data travels the OSI layers, it gets to the Data
> Link layer. This layer adds the physical address (im assuming MAC
> Address) of the next directly connected device. Which device is this
> in the above scenario. I would assume the MAC Address of the switch,
> but I dont know.
In this context, the switch doesn't have any kind of address, it is
invisible to the network.
> What if these same 4 computers were configured in a
> physical bus topology. Which PC is the next directly connected
> device? Is it A or C?
Both.
> Which direction does the bits flow when it
> leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
AIUI a physical bus isn't directional, it goes all ways that it can at
once.
--
-> The email address in this message *IS* Valid <-
| |
| anna c 2002-12-21, 11:24 pm |
| {$PW$}@womar.co.uk (Paul Womar) wrote in message news:<1fnjgkt.1g7g66v12a71ymN%{$PW$}@womar.co.uk>...
> anna c <cwesthaven@hotmail.com> wrote:
>
> > Hey guys. Sorry to be asking so many questions, but I am trying to
> > visualize some things. Here goes: Suppose you have 4 computers: A,
> > B, C, and D all connected to a switch in that order. B wants to send
> > data to D. As the data travels the OSI layers, it gets to the Data
> > Link layer. This layer adds the physical address (im assuming MAC
> > Address) of the next directly connected device. Which device is this
> > in the above scenario. I would assume the MAC Address of the switch,
> > but I dont know.
>
> In this context, the switch doesn't have any kind of address, it is
> invisible to the network.
>
> > What if these same 4 computers were configured in a
> > physical bus topology. Which PC is the next directly connected
> > device? Is it A or C?
>
> Both.
>
> > Which direction does the bits flow when it
> > leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
>
> AIUI a physical bus isn't directional, it goes all ways that it can at
> once.
What do you mean it goes all ways that it can at once? Are the
packets duplicated? Sent twice? Or just one packet goes one way and
another packet may go some other direction? Thanx for all the
replies, anna c
| |
| Paul Womar 2002-12-22, 7:24 am |
| anna c <cwesthaven@hotmail.com> wrote:
> {$PW$}@womar.co.uk (Paul Womar) wrote in message
> news:<1fnjgkt.1g7g66v12a71ymN%{$PW$}@womar.co.uk>...
> > > Which direction does the bits flow when it
> > > leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
> >
> > AIUI a physical bus isn't directional, it goes all ways that it can at
> > once.
>
> What do you mean it goes all ways that it can at once?
I suppose it is a bit difficult to grasp, try and separate the idea of
how each device recognises the information and what it does with it,
with what is actually happening right down at the physical layer. A
cable is a lump of wire, you apply some kind of electrical current and
it will just flow in any and all ways that it can.
> Are the packets duplicated? Sent twice?
No, you have a T connector, so a single cable comes from each host and
into a connector that goes two ways, this is just a bit of dumb cable
passing some electricity (it's probably best that you forget that i is a
packet of data), it has no idea which of these 2 cables needs the signal
so it's split and it goes out both ways. I think of as if whatever
signal is being sent at the time, it fill the whole cable/circuit, so
the whole cable is either a 1 or a 0, each device reads from the cable
simultaneously, although it's no strictly true, with the speed at which
this ishappens it's close enough.
> Or just one packet goes one way and
> another packet may go some other direction?
I think after knowing a bit about physical ring stuff, a bus is a bit
different to understand. AIUI with a physical ring, each machine will
take the packet off of the wire see if it is meant for them, and then
put it back on the wire to the next host. With a bus, all hosts just
read from the wire, if it's for them they they do what tehy need to do,
if it's not then they just forget about it because the host that it was
actually meant for has already recieved it.
| |
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| I think of a bus topology a bit like a radio topology, the packets just get
sent to the wire instead of he air.
The wire in a bus topology is one long continues line, so all nodes hear the
same thing a about the same time.
Mik
"anna c" <cwesthaven@hotmail.com> wrote in message
news:7e04dc8b.0212212058.7ebb97be@posting.google.com...
> {$PW$}@womar.co.uk (Paul Womar) wrote in message
news:<1fnjgkt.1g7g66v12a71ymN%{$PW$}@womar.co.uk>...
> > anna c <cwesthaven@hotmail.com> wrote:
> >
> > > Hey guys. Sorry to be asking so many questions, but I am trying to
> > > visualize some things. Here goes: Suppose you have 4 computers: A,
> > > B, C, and D all connected to a switch in that order. B wants to send
> > > data to D. As the data travels the OSI layers, it gets to the Data
> > > Link layer. This layer adds the physical address (im assuming MAC
> > > Address) of the next directly connected device. Which device is this
> > > in the above scenario. I would assume the MAC Address of the switch,
> > > but I dont know.
> >
> > In this context, the switch doesn't have any kind of address, it is
> > invisible to the network.
> >
> > > What if these same 4 computers were configured in a
> > > physical bus topology. Which PC is the next directly connected
> > > device? Is it A or C?
> >
> > Both.
> >
> > > Which direction does the bits flow when it
> > > leaves computer B's NIC? Towards C? or towards A? Thanx, anna c.
> >
> > AIUI a physical bus isn't directional, it goes all ways that it can at
> > once.
>
> What do you mean it goes all ways that it can at once? Are the
> packets duplicated? Sent twice? Or just one packet goes one way and
> another packet may go some other direction? Thanx for all the
> replies, anna c
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