Hello Open0102,
The traditional comparison of switches and routers is pretty straight
forward. I will assume you are familiar with the seven level OSI model
of network protocols, but if not, check out
http://www.netc.org/network_guide/c.html
for a very readable guide to the OSI model and how Internet protocols
(e.g., TCP, IP, HTTP) map to the seven levels.
In brief, a switch will use the data link (or MAC) address (e.g.,
Ethernet address) to determine where to send a message. For example, I
did a quick check on my ethernet network interface which has address
00:30:65:3f:09:e8
When I plug in this interface to a switch, the switch will note that
address being generated on the wire and send all messages to this
address on that wire. To illustrate with some ASCII art...
S - 00:30:65:3f:09:e8 (A)
W
I - 00:44:68:65:3f:15 (B)
T
C - 00:A0:45:17:22:20 (C)
H
where I have three machines connected to a level 2 switch, a message
from A to B will have address 00:30:65:3f:09:e8 and 00:44:68:65:3f:15
as the destination. The switch looks up the destination address and
sends the message on the second wire. This is a *very* fast operation
and generally works at "wire speed" (i.e., 100 Mbit on a 100 Mbit
switch).
A router on the other hand will examine the data at a higher network
protocol level to determine how to send the message. The Internet
Protocol (IP) is a "routable" protocol because it includes information
used by the intermediate equipment (routers) to determine how to send
the information. As another example you can have
R - the Internet
O
U - 192.168.0.1 (A)
T
E - 192.168.0.2 (B)
R
where the router basically acts as a gateway for two machines to
connect to the Internet. Messages from (A) to (B) are sent directly
between the two systems. Messages from A (or B) to / from the Internet
use the top connection.
This routing operation can be slower because:
- the router must understand the protocol being used (different
protocols put the routing address at different locations in the
message)
- the router will often have rules to determine if a message is to be
sent. For example, a broadcast by A may be sent only to B to prevent
broadcasts to Internet machines.
- there may be more than one path to the destination; the router can
choose the "best" route based on information it has collected (or from
configuration data)
- the router may buffer the data in the case of congestion (the
switch will generally drop data if congestion occurs)
and so on.
However, with modern equipment, you can purchase "switch routers" that
basically do the work of a router at switch speeds [sigh]. For several
good references, I suggest the TechEncyclopedia at
http://www.techweb.com/encyclopedia/
or specifically
http://www.techweb.com/encyclopedia/defineterm?term=LANswitch
http://www.techweb.com/encyclopedia/defineterm?term=layer%32switch
http://www.techweb.com/encyclopedia/defineterm?term=layer%33switch
http://www.techweb.com/encyclopedia/defineterm?term=router
The comparison between IP (Internet Protocol) and IPX (Internetwork
Packet eXchange) has some clear distinctions, but these protocols are
quite similar. This is because they generally map to the same OSI
level. A good illustration is at
http://www.techweb.com/encyclopedia/defineterm?term=IPX
The differences are primarily...
- IP is a broadly adopted protocol, defined through the Internet RFC
(Request For Comment) process while IPX was defined by Novell.
- IP is often layered below TCP (Transmission Control Protocol) or
UDP (User Datagram Protocol) while IPX is often layered below SPX
(Sequence Packet eXchange).
Based on original use, IP (and TCP) was most often used on long haul
networks - the original ARPANet. IPX (and SPX) was most often used on
local area networks - basically connecting PC's to file and print
servers. There were also cases where IPX was encapsulated in IP to
allow Novell systems to exchange data across large networks. In most
cases, use of IPX continues to decline since IP has become much more
broadly adopted by all software vendors (even Novell).
For further information, check out
http://www2.uta.edu/infosys/classes/insy4320/reports/r_2_24.htm
(a general comparison between IPX/SPX and IP/TCP)
http://www.techweb.com/encyclopedia/defineterm?term=NetWare
http://www.unm.edu/~network/presentations/course/chap6/sld055.htm
(a nice chart - part of a larger presentation)
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/netwarep.htm
(one part of a large tutorial on networks - describes NetWare
protocols)
You can find a variety of good information on these topics using
search terms such as:
definition IP IPX comparison
defintion network switch router -prices
[the last phrase included to omit sites trying to sell switches &
routers]
IPX packet format
seven layer network protocol
and so on. If you need additional information, please use the
clarification request and I hope you do well in your studies.
--Maniac |
