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Home > Archive > alt.certification.network-plus > December 2002 > Where does a packet go
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Where does a packet go
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| anna c 2002-12-18, 2:24 pm |
| Hello all,
Let's say you have a bridge connected on part of a LAN (star
configuration). On one side of bridge you have 3 computers A, B, C.
On the other side of bridge you have computers X, Y, Z. Computer A
wants to send data to computer C. Does the packets first go to the
bridge and then the bridge directs them to Computer C or does the
packets go to Computer B and then are sent to Computer C? In other
words, Im wondering do packets leave Computer A's NIC then travels to
the bridge or do they go straight to Computer C? Thanx!!!
| |
| Paul Womar 2002-12-18, 3:24 pm |
| anna c <cwesthaven@hotmail.com> wrote:
> Hello all,
> Let's say you have a bridge connected on part of a LAN (star
> configuration). On one side of bridge you have 3 computers A, B, C.
> On the other side of bridge you have computers X, Y, Z. Computer A
> wants to send data to computer C. Does the packets first go to the
> bridge and then the bridge directs them to Computer C or does the
> packets go to Computer B and then are sent to Computer C? In other
> words, Im wondering do packets leave Computer A's NIC then travels to
> the bridge or do they go straight to Computer C? Thanx!!!
They go to all devices on the same segment, including the bridge, in
this case the bridge will know that it does not need to pass it on so it
will do nthing with it.
--
-> The email address in this message *IS* Valid <-
| |
| Crazymiclo30 2002-12-18, 8:24 pm |
|
>Subject: Re: Where does a packet go
>From: {$PW$}@womar.co.uk (Paul Womar)
>Date: 12/18/2002 3:34 PM Eastern Standard Time
>Message-id: <1fnemgh.1gsrvpv28a83aN%{$PW$}@womar.co.uk>
>
>anna c <cwesthaven@hotmail.com> wrote:
>
>> Hello all,
>> Let's say you have a bridge connected on part of a LAN (star
>> configuration). On one side of bridge you have 3 computers A, B, C.
>> On the other side of bridge you have computers X, Y, Z. Computer A
>> wants to send data to computer C. Does the packets first go to the
>> bridge and then the bridge directs them to Computer C or does the
>> packets go to Computer B and then are sent to Computer C? In other
>> words, Im wondering do packets leave Computer A's NIC then travels to
>> the bridge or do they go straight to Computer C? Thanx!!!
>
>They go to all devices on the same segment, including the bridge, in
>this case the bridge will know that it does not need to pass it on so it
>will do nthing with it.
>--
>-> The email address in this message *IS* Valid <-
>
>
The answer given here is correct. To expand on it to make it more clear. If a
packet is sent from A to C then the bridge, B & C will all receive the packet.
Computers X, Y and Z will not.
crazymiclo
A+
| |
| Andy Barkl 2002-12-18, 10:24 pm |
| "anna c" <cwesthaven@hotmail.com> wrote in message
news:7e04dc8b.0212181211.3bd86942@posting.google.com...
> Hello all,
> Let's say you have a bridge connected on part of a LAN (star
> configuration). On one side of bridge you have 3 computers A, B, C.
> On the other side of bridge you have computers X, Y, Z. Computer A
> wants to send data to computer C. Does the packets first go to the
> bridge and then the bridge directs them to Computer C or does the
> packets go to Computer B and then are sent to Computer C? In other
> words, Im wondering do packets leave Computer A's NIC then travels to
> the bridge or do they go straight to Computer C? Thanx!!!
All workstations would receive a copy of the packet or frame but if their
MAC address was not in the destination of the frame they would discard the
message. The bridge will also receive a copy and if it knows workstation C
is on the same bridge port as workstation A, then it too will discard the
frame.
| |
| Barry Watzman 2002-12-24, 12:24 am |
| All computers on a given network see all packets. The network is a
logical bus, even if it's a physical star.
If the device is truly a bridge, it will pass all packets
unconditionally. A true bridge simply connects two networks that are
physically dissimilar in some way (for example, ABC are ethernet, XYZ
are token ring), "bridging" the two physically dissimilar networks into
a single logical network. A true bridge would pass all packets, thus
all 6 computers (and the bridge) would see all packets, but 5 of the 6
would discard the packet because it was not addressed to them.
However, the term "bridge" is used loosely, and in fact the "bridge"
might technically encompass some capabilities of a switch and/or a
router. In this case, it would apply intelligence and only pass
messages (packets) that needed to get "to the other side". However,
common casual useage aside, if this is what's happening then the device
has capabilities that extend beyond the stict [minimal] definition of a
bridge, encompassing at least some capabilities of either a switch
and/or a router.
anna c wrote:
> Hello all,
> Let's say you have a bridge connected on part of a LAN (star
> configuration). On one side of bridge you have 3 computers A, B, C.
> On the other side of bridge you have computers X, Y, Z. Computer A
> wants to send data to computer C. Does the packets first go to the
> bridge and then the bridge directs them to Computer C or does the
> packets go to Computer B and then are sent to Computer C? In other
> words, Im wondering do packets leave Computer A's NIC then travels to
> the bridge or do they go straight to Computer C? Thanx!!!
| |
| Howard Phillips 2002-12-24, 11:24 pm |
| Please forgive me and feel free to correct me where I err, but I would like
to clarify a few of the terms you threw around. I feel that your response,
while well intentioned may not be completely accurate.
"Barry Watzman" <Watzman@neo.rr.com> wrote in message
news:3E07FC9E.3060209@neo.rr.com...
> All computers on a given network see all packets. The network is a
> logical bus, even if it's a physical star.
Technical point; a 'network' can be anything from 2 computers and a
crossover cable to the entire internet. Here are a few terms to provide a
more precise description of what you might mean:
Segment, this is the logical or physical equivelent of a bus, all packets
generated or broadcast on a segment are seen by all hosts (nodes) on that
segment.
Collision Domain, Cisco term equivelent to a segment.
Broadcast Domain, Cisco term for an area of a network bound by routers.
Broadcasts have all 1s in the MAC address and are seen by all nodes on a
segment regardless of layer 2 switching.
> If the device is truly a bridge, it will pass all packets
> unconditionally. A true bridge simply connects two networks that are
> physically dissimilar in some way (for example, ABC are ethernet, XYZ
> are token ring), "bridging" the two physically dissimilar networks into
> a single logical network. A true bridge would pass all packets, thus
> all 6 computers (and the bridge) would see all packets, but 5 of the 6
> would discard the packet because it was not addressed to them.
More definitions:
Repeater, a device which reconditions and amplifies signals to extend the
physical size of a network. Repeaters forward all traffic to all ports
regardless of MAC or logical address.
Bridge, a device which creates seperate collision domains within a broadcast
domain. Bridges inspect the destination MAC address of packets and only
forward packets to ports on which that MAC address resides.
Translational Bridge, a bridge capable of reformatting packets for different
transport media. For example a translational bridge could connect a token
ring ethernet to a 10baseT ethernet. Since this is still a bridge only
those packets which require translation to reach their destination are
translated.
> However, the term "bridge" is used loosely, and in fact the "bridge"
> might technically encompass some capabilities of a switch and/or a
> router. In this case, it would apply intelligence and only pass
> messages (packets) that needed to get "to the other side". However,
> common casual useage aside, if this is what's happening then the device
> has capabilities that extend beyond the stict [minimal] definition of a
> bridge, encompassing at least some capabilities of either a switch
> and/or a router.
The term bridge is in fact used loosely, however should be used exactly when
preparing for the Network+ test, or any other certification.
I hope I recalled these terms correctly and that I haven't come off as
either and idiot or a pompous XXX.
Howard Phillips
> anna c wrote:
> > Hello all,
> > Let's say you have a bridge connected on part of a LAN (star
> > configuration). On one side of bridge you have 3 computers A, B, C.
> > On the other side of bridge you have computers X, Y, Z. Computer A
> > wants to send data to computer C. Does the packets first go to the
> > bridge and then the bridge directs them to Computer C or does the
> > packets go to Computer B and then are sent to Computer C? In other
> > words, Im wondering do packets leave Computer A's NIC then travels to
> > the bridge or do they go straight to Computer C? Thanx!!!
>
| |
| Gareth 2002-12-27, 3:24 pm |
|
"Howard Phillips" <Howard.Phillips@removethis.cosmic.com> wrote in message
news:PfbO9.36891$VA5.5904713@news1.news.adelphia.net...
> Please forgive me and feel free to correct me where I err, but I would
like
> to clarify a few of the terms you threw around. I feel that your
response,
> while well intentioned may not be completely accurate.
>
> "Barry Watzman" <Watzman@neo.rr.com> wrote in message
> news:3E07FC9E.3060209@neo.rr.com...
> > All computers on a given network see all packets. The network is a
> > logical bus, even if it's a physical star.
>
> Technical point; a 'network' can be anything from 2 computers and a
> crossover cable to the entire internet. Here are a few terms to provide a
> more precise description of what you might mean:
>
> Segment, this is the logical or physical equivelent of a bus, all packets
> generated or broadcast on a segment are seen by all hosts (nodes) on that
> segment.
>
> Collision Domain, Cisco term equivelent to a segment.
>
> Broadcast Domain, Cisco term for an area of a network bound by routers.
> Broadcasts have all 1s in the MAC address and are seen by all nodes on a
> segment regardless of layer 2 switching.
>
> > If the device is truly a bridge, it will pass all packets
> > unconditionally. A true bridge simply connects two networks that are
> > physically dissimilar in some way (for example, ABC are ethernet, XYZ
> > are token ring), "bridging" the two physically dissimilar networks into
> > a single logical network. A true bridge would pass all packets, thus
> > all 6 computers (and the bridge) would see all packets, but 5 of the 6
> > would discard the packet because it was not addressed to them.
>
> More definitions:
> Repeater, a device which reconditions and amplifies signals to extend the
> physical size of a network. Repeaters forward all traffic to all ports
> regardless of MAC or logical address.
>
> Bridge, a device which creates seperate collision domains within a
broadcast
> domain. Bridges inspect the destination MAC address of packets and only
> forward packets to ports on which that MAC address resides.
>
> Translational Bridge, a bridge capable of reformatting packets for
different
> transport media. For example a translational bridge could connect a token
> ring ethernet to a 10baseT ethernet. Since this is still a bridge only
> those packets which require translation to reach their destination are
> translated.
>
> > However, the term "bridge" is used loosely, and in fact the "bridge"
> > might technically encompass some capabilities of a switch and/or a
> > router. In this case, it would apply intelligence and only pass
> > messages (packets) that needed to get "to the other side". However,
> > common casual useage aside, if this is what's happening then the device
> > has capabilities that extend beyond the stict [minimal] definition of a
> > bridge, encompassing at least some capabilities of either a switch
> > and/or a router.
>
> The term bridge is in fact used loosely, however should be used exactly
when
> preparing for the Network+ test, or any other certification.
>
> I hope I recalled these terms correctly and that I haven't come off as
> either and idiot or a pompous XXX.
> Howard Phillips
> > anna c wrote:
> > > Hello all,
> > > Let's say you have a bridge connected on part of a LAN (star
> > > configuration). On one side of bridge you have 3 computers A, B, C.
> > > On the other side of bridge you have computers X, Y, Z. Computer A
> > > wants to send data to computer C. Does the packets first go to the
> > > bridge and then the bridge directs them to Computer C or does the
> > > packets go to Computer B and then are sent to Computer C? In other
> > > words, Im wondering do packets leave Computer A's NIC then travels to
> > > the bridge or do they go straight to Computer C? Thanx!!!
All seems okay Howard, but to be honest I think the biggest error would be
in calling the data package a "packet" - frame would be more correct :-)
G.
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