The Need for Speed

The Need for Speed!

A Technical Briefing for Those Interested in Bits and Bytes

During the course of developing this information, I came across a number of subtle but noteworthy differences between system peripherals and networks that can easily mislead individuals comparing disk I/O specifications with network I/O specifications.

While theoretical throughput specifications suggest speed, they mislead in the same way horsepower specifications oversimplify the speed of an automobile. Throughput specifications suggest a potential limit on the maximum speed.

A majority of today's communications protocols use layering concepts outlined in the OSI model. Each layer decreases the " user " data throughput below the maximum by taking a percentage of the bandwidth for layer-to-layer information. In contrast, peripheral devices and system bus communications use electrical signals at board level. Maximum throughput is much more theoretical with the potential for bottlenecks created by a specific card design. In the end, these "cards" have to communicate over wire, fiber, or wireless. As technology pushes processor speeds, all of these communication methods tend to converge.

The figures in Table A-1 may aid individuals interested in a comparison.

Table A-1. Communication Mechanisms, Protocols, Speeds, and Distances

Type	Name	Maximum Throughput	Distance
Connection Service	Dial-Up Modem	9.6, 14.4, 28.8, 33.6, 56 Kbps
Network Service	Packet Switched (X.25)	56 Kbps
Network Service	Switched 56/64	56 Kbps, 64 Kbps
Connection Service	Fractional T1	N x 64 kbps
PC Connection	Serial Port	115 Kbps
Network Service	ISDN BRI	BRI 64 “128 Kbps
Connection Service	ISDN DSL (IDSL)	144 Kbps
Printer Connection	Standard PC Parallel Port	115 KB/s (920 kbps)
Network Service	ISDN PRI	PRI 1.544 Kbps
Connection Service	Consumer DSL (CDSL)	128 Kbps Upstream 1 Mbps Downstream
Connection Service	G.Lite ADSL	520 Kbps Upstream 1.5 Mbps Downstream
Connection Service	Rate Adaptive DSL (RADSL)	1 Mbps Upstream 7 Mbps Downstream
Connection Service	Asymmetric DSL (ADSL)	1 Mbps Upstream 8 Mbps Downstream
Connection Service	T1	24 x 64 Kbps = 1.5 Mbps
Connection Service	Symmetric DSL (SDSL)	160 Kbps 208 Kbps 784 Kbps 1.5 Mbps
Connection Service	High Bit Rate DSL (HDSL/HDSL-2)	768 Kbps 44 Mbps (HDSL-2) 1.544 Mbps 2.048 Mbps
Connection Service	Very High Bit Rate DSL (VDSL)	1.6 “6.4 Mbps Upstream 13 “52 Mbps Downstream
Local Network	Ethernet	10 Mbps (shared)	100 m
Local Network	Wireless Ethernet	11 Mbps (shared) & 54 Mbps
Local Network	Switched Ethernet	10 Mbps (node to node)	100 m
Local Network	Token Ring	4, 16 Mbps	125 m
Device Interface	USB Version 1.0	12 Mbps
Personal Network	Wireless Personal Area Network “ "Bluetooth"	20 Mbps (shared)	10 m
Card Interface	PCMCIA Bus (16-Bit)	20 Mbps
Printer Interface	ECP/EPP parallel port	3 MB/s (24 Mbps)
Card Interface	PCMCIA Bus (32-bit) CardBus	40 Mbps
Device Interface	SCSI-1	5 MB/s (40 Mbps)	6m
Connection Service	T3	672 x 64 kbps = 44.7 Mbps
Network Service	Frame Relay	56 Kbps “45 Mbps
Network Service	Sonet OC-1	51.84 Mbps
System Bus	ISA “ Original PC	8 MB/s (64 Mbps)
Device Interface	SCSI-2 Fast SCSI, Fast-10	10 MB/s (80 Mbps)	3m
Local Network	Fast Ethernet	100 Mbps	100 m
Local Network	FDDI/CDDI	100 Mbps	10 km
Local Network	Fast Token Ring	100 “128 Mbps	125 m
Device Interface	ESCON	17 MB/s (136 Mbps)	3 km
Device Interface	IDE	3.3 “16.7 MB/s (26.4 “133.6 Mbps)
Network	Sonet OC-3	155.52 Mbps
Device Interface	Ultra SCSI, Fast-20	20 MB/s (160 Mbps)	1.5 m
Device Interface	SCSI-2, Fast Wide SCSI, Fast-10	20 MB/s (160 Mbps)	1.5 m
Device Interface	UltraIDE	33 MB/s (264 Mbps)
Device Interface	Ultra Wide SCSI, Fast-20	40 MB/s (320 Mbps)	1.5 m
Device Interface	Ultra2 SCSI	40 MB/s (320 Mbps)	12 m
System Bus	Micro Channel “ Original	40 MB/s (320 Mbps)
Device Interface	IEEE-1394 Firewire	100 “400 Mbps	4.5 m
Device Interface	USB Version 2.0	480 Mbps
Network Device	Sonet OC-12	622.08 Mbps
Device Interface	SCSI-3, Ultra2 Wide (U2W) SCSI, Ultra2 LVD SCSI, Fast-40	80 MB/s (640 Mbps)	12 m
Device Interface	FICON,	100 MB/s	10 km
Storage Network	Fibre Channel (FC-AL)	(800 Mbps)
Local Network	Gigabit Ethernet	1000 Mbps	550 m
Device Interface
Storage Network	iSCSI	1000 Mbps
System Bus	PCI (32-bit/33 MHz)	132 MB/s (1,056 Mbps)
System Bus	VESA VL-Bus (Limited to 486 CPU)	132MB/s (1,056 Mbps)
System Bus	Micro Channel “ RS6000	160 MB/s (1,280 Mbps)
Device Interface	Ultra3 SCSI, Ultra160/m	160 MB/s (1,280 Mbps)	12 m
Device Interface	SSA	160 MB/s (1,280 Mbps)	2.4 km
System Bus	PCI (64-bit/33 MHz) PCI (32-bit/66 MHz)	264 MB/s (2,112 Mbps)
System Bus	PCI-X (32-bit/66 MHz)	264 MB/s (2,112 Mbps)
Network	Sonet OC-48	2,488.32 Mbps
Device Interface	Fiber Channel (FC-AL)	100 “400 MB/s (800 “3,200 Mbps)
System Bus	PCI (64-bit/66 MHz) (Limit 1 per System)	528 MB/s (4,224 Mbps)
System Bus	PCI-X (64-bit/66 MHz) PCI-X (32-bit/133 MHz)	528 MB/s (4,224 Mbps)
System Bus	PCI-X (64-bit/133 MHz) (limit 1 per system)	1,060 MB/s (8,480 Mbps)
Connection Service
Network Service	ATM	1.5, 25, 100, 155, 622, 2,488, and 9,953 Mbps
Network	Sonet OC-192	9,953.28 Mbps
Network	Sonet OC-768	38,813.12 Mbps

Please do not consider this a trustworthy source for data in critical situations. The data, collected from numerous Web sites, may contain errors or outdated information. Occasionally, different sites contained different data. In attempting to provide the theoretical maximum throughput, the table lists the highest throughput found. This list is not anywhere near conclusive.