networking questions...

Mirlyn · 09-12-2003

Hey all....long time no see!

What is the exact defintion of full-duplex? I understand the two-way communication, but what about speeds. Does 100m FD networking use 100m upstream and 100m downstream, or is it 50m/50m? What about wireless?

As we all know, DLink has 22mbps stuff. How does this work? Does the 256-bit require their own software? Reason I was asking was related to the above question. I thought FD meant full speeds either way, so 11m upstream 11m downstream = 22mbps. And 128bit encryption on the upstream, 128 on the downstream = 256bit. Am I wrong here?

I installed a netgear gigabit card in a server about six months ago which claimed it would do effectively 2Gbps in Full Duplex mode. 1 up + 1 down?

Just curious....

~Mirlyn

G8tK33per · 09-12-2003

Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. For example, on a local area network with a technology that has full-duplex transmission, one workstation can be sending data on the line while another workstation is receiving data. Full-duplex transmission necessarily implies a bidirectional line (one that can move data in both directions).

Mirlyn · 09-12-2003

Quote:

Originally posted by G8tK33per
Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. For example, on a local area network with a technology that has full-duplex transmission, one workstation can be sending data on the line while another workstation is receiving data. Full-duplex transmission necessarily implies a bidirectional line (one that can move data in both directions).

I understand that, but what about the speeds?

Thorn · 09-12-2003

Roughly:

Full duplex at 11mbps = 11mbps thoughput
Half duplex at 11mbps = 5.5mbps thoughput

(There is always a little bit of overhead for error checking, etc.)

The easiest way to explain full and half duplex that people are familiar with are telephone and two-way radios (police, fire, etc.)
Telephone is full duplex. Both parties can talk at the same time, and both can be heard at the same time. Two-way radio on the other hand is half duplex: One person talks while the other listens. Then they switch.

Same thing applies with networking; wired is similar to a telephone, wireless is, in fact, a two-way radio. It is half duplex. One channel is shared to communicate between two units, taking turns. Each unit talks at full speed (11mbps) but they are spending half the time listening, so you only get have the speed.

The way to get full duplex with radios is to use seperate channels/freqs:
Unit 1 talks on ch1, and listens on ch2.
Unit 2 talks on ch2, and listens on ch1.

Does that make it any clearer, or did I just confuse you more?

Mirlyn · 09-12-2003

Quote:

Originally posted by Thorn
Roughly:

Full duplex at 11mbps = 11mbps thoughput
Half duplex at 11mbps = 5.5mbps thoughput

(There is always a little bit of overhead for error checking, etc.)

The easiest way to explain full and half duplex that people are familiar with are telephone and two-way radios (police, fire, etc.)
Telephone is full duplex. Both parties can talk at the same time, and both can be heard at the same time. Two-way radio on the other hand is half duplex: One person talks while the other listens. Then they switch.

Same thing applies with networking; wired is similar to a telephone, wireless is, in fact, a two-way radio. It is half duplex. One channel is shared to communicate between two units, taking turns. Each unit talks at full speed (11mbps) but they are spending half the time listening, so you only get have the speed.

The way to get full duplex with radios is to use seperate channels/freqs:
Unit 1 talks on ch1, and listens on ch2.
Unit 2 talks on ch2, and listens on ch1.

Does that make it any clearer, or did I just confuse you more?

Gotchya. Basically same-sized pipe, more traffic; hence the halved-speed.

Thanks!

09-12-2003	#1 (permalink)
Mirlyn social engineer Join Date: Aug 2002 Location: Wichita, Kansas Posts: 48	networking questions... Hey all....long time no see! What is the exact defintion of full-duplex? I understand the two-way communication, but what about speeds. Does 100m FD networking use 100m upstream and 100m downstream, or is it 50m/50m? What about wireless? As we all know, DLink has 22mbps stuff. How does this work? Does the 256-bit require their own software? Reason I was asking was related to the above question. I thought FD meant full speeds either way, so 11m upstream 11m downstream = 22mbps. And 128bit encryption on the upstream, 128 on the downstream = 256bit. Am I wrong here? I installed a netgear gigabit card in a server about six months ago which claimed it would do effectively 2Gbps in Full Duplex mode. 1 up + 1 down? Just curious.... ~Mirlyn

09-12-2003	#2 (permalink)
G8tK33per Asshole Emeritus Join Date: May 2003 Location: Goomba's Booty Boardwalk Posts: 6,128	Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. For example, on a local area network with a technology that has full-duplex transmission, one workstation can be sending data on the line while another workstation is receiving data. Full-duplex transmission necessarily implies a bidirectional line (one that can move data in both directions). __________________ "My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention." Sons of Confederate Veterans

09-12-2003	#4 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	Roughly: Full duplex at 11mbps = 11mbps thoughput Half duplex at 11mbps = 5.5mbps thoughput (There is always a little bit of overhead for error checking, etc.) The easiest way to explain full and half duplex that people are familiar with are telephone and two-way radios (police, fire, etc.) Telephone is full duplex. Both parties can talk at the same time, and both can be heard at the same time. Two-way radio on the other hand is half duplex: One person talks while the other listens. Then they switch. Same thing applies with networking; wired is similar to a telephone, wireless is, in fact, a two-way radio. It is half duplex. One channel is shared to communicate between two units, taking turns. Each unit talks at full speed (11mbps) but they are spending half the time listening, so you only get have the speed. The way to get full duplex with radios is to use seperate channels/freqs: Unit 1 talks on ch1, and listens on ch2. Unit 2 talks on ch2, and listens on ch1. Does that make it any clearer, or did I just confuse you more? __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

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