Basic megabit/megabyte question

My understanding is that a small b indicates bits, and a capital B indicates bytes. So the above should be correct...

For a data oriented chart of both Bits and Bytes (and several other conversions/definitions) check out

11th commandment. Thou shalt not abrev.

Others have answered your question about abreviations. I'll answer the question that I think you meant to ask, which is how fast can you move data at the various speeds.

A 24Mbit/sec OFDM wireless association or connection, will yield about

12Mbits/sec TCP thruput after dealing with all the overhead, sliding windows, 802.3 enacapsulation, timing delays, and management frames. An 11Mbit/sec CCK connection will yield about 4-5.5Mbits/sec thruput.

Both wireless speeds are faster than your 1.5 or 3Mbit/sec DSL service, which also has overhead an inefficiencies. You'll get about

1.2Mbits/sec thruput with 1500/256Kbits/sec service, and about 2.2Mbits/sec thruput with 3000/384Kbits/sec service.

Personally, I would get the 3Mbit/sec service because it usually offers higher upload speeds, which is important if you're running servers, playing VoIP, or doing the VPN thing.

Charter doesn't have megabyte service, they have megabit service. Any wireless will be faster.

Tom

One thing to note is that in SI abbreviations a small emm is milli. You want a big Emm, which is mega. :-)

Divide by something between eight and ten, to allow for checksums, parity etc. And expect data throughput to be about 70% of the in-air bandwidth, due to protocol headers etc.

Are you sure the service its 1Megabyte, not one megabit? Very few ISPs offer megabyte-rated services except via leased line, and then you're into $$$.

"Peter Pan" wrote in news: snipped-for-privacy@individual.net:

Aaaaaargh!

NO - and the link above merely compounds the errors. It is *full* of inaccuracies.

Units and their abbeviations are defined in SI units. Have a look here:

There is *no* standard abbreviation for bit There is *no* standard abbreviation for byte Indeed, I'm not even sure if there is a standard for how many bits there are in a byte, although of course 8 is usual...

Prefixes: m = milli = 10**-3 k = kilo = 10**3 M = mega = 10**6 G = giga = 10**9

Units: s = second

There is *no* abbreviation for 'per'.

Correct:

1 Mbit/s = 1 megabit per second 1 Mbyte/s = 1 megabyte per second

WRONG:

1 mbps - simply wrong, and a source of confusion 1 MBps - ditto

There is always a risk of confusion when incorrection or inaccurate abbrevaitions are used, as in this case. There is always a temptation to abbreviate, but it simply leads to confusion.

So, to answer the question:

11 mbps is an incorrect abbreviation for 11 Mbit/s, the highest speed allowed by the IEEE 802.11b standard, and also a intermediate step- down speed allowed by the IEEE 802.11g standard.

24 mbps is an incorrect abbreviation for 24 Mbit/s, an intermediate step-down speed allowed by IEEE 802.11g.

11 Mbit/s = 1.375 Mbyte/s 24 Mbit/s = 3 Mbyte/s

The term 'bps' is (of course!) not used in IEEE 802.11, but does erroneously appear in one place in IEEE 802.11b where it cross-refers to IEEE 802.11 speeds. It is not used in IEEE 802.11g.

Slightly more seriously, confusion could be easily avoided by sticking to 'proper' abbreviations and not making them up as we go along. I blame the marketing people...

If the price is reasonable, go with the 3 Mbit/s service - this will be more responsive if you have several machines on your network, or if you do a lot of downloading. The 1 Mbit/s service will probably also be fine for most purposes.

Note that the line speed is a limiting factor. Your local wireless network speeds are very much faster and do not affect Internet speeds, which are constrained by your wide area connection.

Hope this helps

Fastest I've used was RoadRunner in 1998. There were only 500 of us in the beta in Austin. We saw 5-6mbps (NOT Mbps). Anyone advertising with a BIG M is manipulating it.

Go, Tom! Cut to the chase! After reading the pedantic posts that actually contained the same answer, somewhere, I think, maybe...

I have Mediacom Cable. "Download Speeds up to 3MBps." My 802.11b card did the same speed downloads as my wired 100BaseT. The cable is the slow part.

Today,

for my cable-wireless at 36 Mbps (802.11g) Your download speed : 1426846 bps, or 1393 kbps. A 174.1 KB/sec transfer rate. Your upload speed : 247511 bps, or 241 kbps.

I can transfer at about 20Mbps between my laptop and a wired computer. The cable is the slow part.

"Tom Scales" wrote in news:w_eNd.17151 $ snipped-for-privacy@bignews1.bellsouth.net:

5-6 millibits per second is pretty slow, whereas 5-6 megabits per second is fairly respectable.

Maybe you've mixed up m/M versus b/B ?

Nope, not confused at all.

MB = Megabytes mB = megabits.

Clear to you now?

I have a wired/wireless (802.11b) setup on Comcast Cable. The wired part shows 100.0 Mbps connection on the wired side and when using my laptop/pda on the wireless side it typically shows 11Mbps. Confusing for me is that when using the wireless side with either laptop or pda it really doesn't appear to be much slower than the desktops on the wired side. Maybe I'm just not observing as critically as I should.

Are these figures simply "marketing" numbers? I assume these numbers should actually vary with the load on the cable system.

How or where can I actually read "real" xfer values...(Win-XP Home SP2)?

TIA

One has to assume he meant Mbps vs MBps.

MB is the common abbreviation for MegaByte, but I've never seen mB for megabit; the common abbreviation for Megabit is Mb.

M is the well-defined standard prefix for Mega. The usage of B for Byte and b for bit is common, and does appear in some standards documents (i.e., the Serial ATA standard), but it is not as universally recognized as is M for 10^6. I wish that the world would stick to B=Byte=8b to avoid confusion.

100 Mb/s and 11 Mb/s are the peak bit rates on the wired and wireless segments. They are real (technical, not just marketing) numbers, but they do not pretend to represent the STR (Sustained Transfer Rate).

With a Comcast cable, the STR limit is due to the cable-side of the cable modem, not the LAN-side of the wired or wireless connection to the modem.

In my area, Comcast delivers up to 4 Mb/s downhill, and roughly 10% of that uphill. Note that the 4 Mb/s on the Comcast cable (downhill) is another peak data rate number; since the cable is shared between you and *lots* of your neighbors, you may see 4 Mb/s for one download and a fraction of that for the next download.

Comcast is usually 3Mbits/sec. You'll get about 2.5Mbits/sec thruput.

The 100Mbits/sec ethernet speed is the connection speed. If you've got two decent computahs, connected on a LAN through an ethernet switch, you'll get about 85Mbits/sec thruput when copying files between the two computahs.

Again, that's the connection speed. You'll get about 4-5.5Mbits/sec thruput.

Maybe some benchmarking would be appropriate. Since you have Windoze XP on the laptop, fire up the "Task Manager" and select the "Networking" tab. It should show the network preformance numbers.

are also a bunch of performance meters avaiable for download. I use SNMP to get my numbers, but that's probably overkill for this test. Try "IPerf": all else fails, find a big file and use a stopwatch to time how long it takes to copy over the network. Then, do the math.

Nope. They're for real. It's kinda like buying a car with a 120mph speedometer. It might go 120mph under totally ideal conditions, but reality has a bad habit of lowering results. In the wireless case, the problem is that there is considerable overhead and variables. Besides congestion and constipation on the cable system, there are other things that will slow down wireless traffic. For example (ignoring slowdowns caused by applications): Signal quality (i.e. S/N ratio). CCK vs OFDM modulation Encryption Encryption level Router filters MAC address filters 802.3 encapsulation RF interference RF reflections and multipath Co-channel users Use of a repeater or WDS repeater. Hubs instead of switches Slow computah Whatever else I forgot. Every one of these will slow things down from the mythical 11Mbits/sec to a lower number. The exact amount of reduction varies with implimentation, severity (in the case of interference and multipath), and signal quality. A few are optional, but most are all part of the

802.11 puzzle.

"Task Manager" -> Networking -> Ethernet

Which Numbers? 100Mbps is a typical wired connection. 11Mbps is a typical wireless connection. something less is a typical cable connection. What does your cable company claim? 3Mbps? That is easily attainable by either wired or wireless, so you won't see any difference. The cable is the slow part.

Yes, I already admitted my 'pomposity'. I apologize for my unneeded arrogance. Don't know what came over me.

That will work for his internet download and upload speed. However, he wanted the speed of his 802.11b wireless connection, not the internet connection. The internet connection will be limited to about

3Mbits/sec, while the 11Mbit/sec wireless will be somewhat faster. The only way to get a real number for 802.11b is to do it locally and not through the internet. However, I forgot that he only has one computah, which will make using Iperf difficult.

Agreed. It's the best. However, every once in a while, I find that it's either overloaded, or yielding bizarre results. So, I go hunting for an internet speed test at:

offers about 30 test sites for California. For SBC DSL tests, I use: 'm not sure if Comcast has a local speed test tool. Methinks not, but I'm not sure.

Instead of Iperf, methinks maybe something more "windowish" might be appropriate like "Netstat Live":

played with it a few times, got some funny numbers on gigabit LAN connections, and went back to SNMP. It will probably work well enough for this test. I just installed it on my W2K system. No smoke or fire, yet.

OK. Better than the Task Manager thing but make ugly graphs. (Can you tell that I don't use these much?) I prefer SNMP for everything using Net-SNMP for grabbing numbers or MRTG for making pretty graphs.

methinks this might be a major challenge for a beginner, so I won't suggest using SNMP.

"Tom Scales" wrote in news:KGoNd.21522 $ snipped-for-privacy@bignews4.bellsouth.net:

per

Time you stopped digging Tom.

Hej CJ.

This is my experience with wireless speed, compared to internet connection

I have an internet connection based on ADSL. 4 Mbit download and 768Kbit upload.

My 11 Mbit 802.11b wireless device transfer around 3,5Mbit per second maximum. My 54 Mbit 802.11g wireless device transfer the full internet speed 4Mbit. (Obviously even more if the internet connection is faster).

Be aware that an 11 Mbit wireless device will only transfer around 3-5 Mbit each direction because the specification is half duplex. Same is for 54 Mbit g device but faster of cource.

Regards

Allan

"CJ" skrev i en meddelelse news:_W7Nd.10082$ snipped-for-privacy@fe04.lga...