On 5 aug 2008, at 16:53, Joel M. Halpern wrote:
Well, I personally would not recommend that $30 investment.
My machine speaks B and G (I don't think it speaks N, although the
site monitor can detect that.) I had repeatedly awful connectivity.
So I do not think that telling people to use 11g is an answer.
There are three issues. Two are immediately dependent on support for
802.11b and one is mostly unrelated.
Issue 1:
802.11b stations must send and receive at a maximum of 11 Mbps, which
is only 20% of the speed of a 802.11g station. The former can reach a
throughput of about 700 kilobytes/sec on a good day, the latter 3 MB/
sec. So a b user using 175 kB/sec uses up 25% of the total channel
capacity but if that user upgrades to g, it's only 6% of the total
channel capacity. So fewer b users means more capacity for everyone
else.
Issue 2:
802.11g and n stations use encodings that 802.11b stations don't
understand. To avoid collisions, whenever a b station is present on
the channel, g stations use an extra two-packet exchange to reserve
the channel before sending the actual data. This reduces 802.11g
performance by about 50%.
Issue 3:
In order to make sure that everyone receives all broadcasts and
multicasts (which is a significant amount of traffic on a network with
hundreds of nodes that are all ARPing, DHCPing, RAing and many use
multicast DNS), these are sent at a very low speed, typically 2 Mbps.
This speed can usually be set higher at the expense of some reliability.
So using 802.11g won't help an individual user much, but moving as
many users as possible to 802.11g will help some, and turning off
802.11b support will probably help a lot.
Increasing broadcast speed will also help.
And 11a has much to limited use for me to pay extra to have it
included in my laptop.
Well, it gets you fast and reliable connectivity at IETF meetings...
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