Archived from groups: alt.internet.wireless (
More info?)
On Thu, 16 Dec 2004 16:58:58 -0800, Kevin Hill <h@k.com> wrote:
>Hi, can you explain why you think routing at L3 is better
>than L2?
Layer 2 is bridging, not routeing.
Layer 3 is routeing.
(Is it routeing or routing?)
A bridge has no concept of CIDR or netmask. Therefore, you can't just
say "take all the traffic on this here network and shove it through a
gateway over to yonder network". That's easy with a router. With
bridging, each MAC address is unique with no guaranteed commonality
with other machines on the same network. Therefore, to do routeing on
Layer 2, you would need a route for every single last lousy MAC
address on the network. That's not very practical or useful.
Also, with bridging, the manufactory assigns the MAC address (although
it can be changed). With routeing, the network admin or the DHCP
server assigns the IP address, giving much more control over
organization, topology, and routeing on Layer 3.
Also, Layer 2 has no concept of services, such as http, ftp, telnet,
etc. Layer 3 routeing allows you to control traffic by these
services. Layer 2 only knows about ethernet and cannot distinguish
the different types of traffic.
ALL (and I do mean all) wireless contraptions are Layer 2 bridges. A
wireless bridge know nothing about Layer 3 (TCP/IP) features and
functions. All it knows is ethernet and MAC addressing. If the
destination MAC address is across the bridge, the traffic will pass
over the bridge. If not, it won't pass. More simply, all 802.11
wireless does is encapsulate 802.3 ethernet packets, send them over a
radio link, and reconstruct the original 802.3 ethernet packets at the
destination end. Crudely, it's an extension cord for ethernet.
A wireless router is nothing more than a wireless bridge with an
ethernet router glued onto one of the wireless (switch) ports. The
function of the router is quite independent of the wireles bridge
section.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice
http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# jeffl@cruzio.com AE6KS