Categorically, cut-through switches begin forwarding frames before they entirely receive them--on the fly. In our tests, the six cut-through switching hubs exhibited slightly shorter latency than the 23 store-and-forward switches. Latency varies according to many factors, including how well a switch "slices" or "cuts" a frame before transmitting it and whether it reads just the first 6 bytes for a destination address, the first 12 bytes for the entire MAC (media access control) address (including the source address), or the entire frame for a CRC (cyclic redundancy check). In the last case, the switch is using store-and-forward techniques. Forwarding delays also increase when incoming traffic is hampered by outgoing traffic.
Of the cut-through switches, only the NetWiz TurboSwitch-2000 lets you preselect a latency value. Most of the others opt for
the middle ground and read the entire MAC address (necessary for virtual LAN support) before transmission.
Although a cut-through switch can achieve lower forwarding delays than a store-and-forward switch, it may suffer from errors received during its travels. This is likely because switches can detect errors only by reading the end of each frame. Error propagation is a particular concern with Ethernet, because the Ethernet protocol specifies the generation of corrupted and truncated frames for flow control. The TurboSwitch-2000 has a clever workaround for this problem. Although it doesn't block bad frames, it does calculate CRCs for each frame and reports statistics back to the management station for monitoring and possibly for an error-correction decision at a higher protocol layer.
Three of the six cut-through switches we tested are stackable, and three are rack-mountable. Of the stackable models, only Ornet's LANbooster 2000 provides a pluggable switch module. This design lets you swap a def
ective switch with a standby unit to allow continued network operation while the defective switch module undergoes repair. The other two stackable cut-through switches--Hewlett-Packard's EtherTwist LAN Switch and the IBM 8271 EtherStreamer Switch Model 1--are not expandable. The only way to expand them is by stacking more switch units.
The three rack-mountable cut-through switches allow for expansion. Kalpana's three-slot EtherSwitch EPS-2115M can be expanded to 15 ports, the Fibronics GigaHub supports 72 ports, and the NetWiz TurboSwitch-2000's Maxi Chassis (which is a big brother of the 18-port Mini Chassi unit) supports 120 ports per chassis. The maximum number of supported MAC addresses on each port varies from 1700 (for the Kalpana EtherSwitch EPS-2115M, HP's EtherTwist LAN Switch, IBM's 8271 EtherStreamer Switch Model 1, and Fibronics' GigaHub) up to 131,000 addresses for Ornet's LANbooster 2000.
Cut-through switches perform slightly better than store-and-forward switches in standard NetWa
re IPX protocol tests. On average, the cut-through switches show an appreciable performance advantage over their store-and-forward counterparts in the Excel and Word for Windows tests, but the results are reversed in the FoxPro for Windows tests. Under burst-mode IPX, the performance gap remains essentially the same for Excel, it's slightly narrowed for Word, and it reverses for FoxPro in favor of the store-and-forward switches. We expected the Word test results, because Word file I/O activity is basically similar to a file transfer activity. Simple read/write requests should closely correlate with latency characteristics, and Excel's file I/O characteristics are similar.
There is a huge performance gap between the best and the worst cut-through switches. This reflects how the various switch designs, architectures, and methods of handling latency affect performance. The TurboSwitch-2000 and LANbooster 2000 are considerably faster than the other four.
WEIGHTING FOR BEST OVERALL
P
ERFORMANCE 75%
FEATURES 15%
USABILITY 10%
A HIGHLY EXPANDABLE SWITCHING MEISTER
BEST OVERALL:
NetWiz TurboSwitch-2000
The TurboSwitch-2000 edges out Ornet's LANbooster 2000 for the best
performance in our benchmark tests; the two totally outdistance the
other four products. With its combination of back-pressure flow
control and high frame rates (up to 10 million frames per second in
its maximum configuration), the TurboSwitch-2000 performs superbly in
both the low-level and applications benchmarks. The NetWiz switch
also has the best features score and offers the most expandability of
all the cut-through switching hubs.
PRICE PER OVERALL
PORT TEST EVALUATION
VENDOR/MODEL CONFIGURATION SCORE
=====================================================================
BEST
NetWiz TurboSwitch-2000 $570 9.45
RUNNER-UP Ornet Data LANbooster 2000 $795 8.75
RUNNER-UP Fibronics GigaHub $739 8.54
RUNNER-UP Kalpana EtherSwitch EPS-2115M $650 8.05
VENDOR/MODEL PERFORMANCE FEATURES USABILITY
=============================================================================
BEST NetWiz TurboSwitch-2000 ***** **** ****
RUNNER-UP Ornet Data LANbooster 2000 ***** ** ***
RUNNER-UP Fibronics GigaHub **** *** ****
RUNNER-UP Kalpana EtherSwitch EPS-2115M *** *** *****
BUFFER MAX. MAX.
SIZE PORTS MAC SWITCH-
PER PER ADDRESS/ ING
VENDOR/MODEL PORT SWITCH PORT RATE
===============================================================================
BEST NetWiz TurboSwitch-2000 256 KB 120 64,000 10 million
RUNNER-UP Ornet Data LANbooster 2000 256 KB 12 131,000 176,400
RUNNER-UP Fibronics GigaHub 256 KB 72 1700 44,640
RUNNER-UP Kalpana EtherSwitch EPS-2115M 512 KB 15 1700 223,200
KEY
Ratings from 1 to 5: * is the lowest; ***** is the highest.
A PICK-ME-UP FOR TIRED LANS
BEST STACKABLE:
Ornet LANbooster 2000
If you work with a small workgroup that doesn't require expansion
options or multiple LAN support capabilities, Ornet's LANbooster 2000
is the perfect choice. Performance-wise, it finished right on the
heels of the NetWiz TurboSwitch-2000. Its zero-packet-loss
back-pressure technique accounts for much of this sterling
performance. And in the case of a switch module failure, you can swap
the 1
2-port switch module to minimize downtime.
PRICE PER OVERALL
PORT TEST EVALUATION
VENDOR/MODEL CONFIGURATION SCORE
====================================================================
BEST Ornet Data LANbooster 2000 $795 8.75
RUNNER-UP HP EtherTwist LAN Switch $570 7.89
VENDOR/MODEL PERFORMANCE FEATURES USABILITY
============================================================================
BEST Ornet Data LANbooster 2000 ***** ** ***
RUNNER-UP HP EtherTwist LAN Switch **** *** ***
BUFFER MAX. MAX.
SIZE PORTS MAC SWITCH-
PER PER ADDRESS/ ING
VENDOR/MODEL
PORT SWITCH PORT RATE
=============================================================================
BEST Ornet Data LANbooster 2000 256 KB 12 131,000 176,400
RUNNER-UP HP EtherTwist LAN Switch 128 KB 6 1700 14,880
KEY
Ratings from 1 to 5: * is the lowest; ***** is the highest.
IT'S EXPANDABLE, FAST, AND FLEXIBLE
BEST RACKMOUNTABLE:
NetWiz TurboSwitch-2000
Highly modular, with plenty of room for expansion, the
TurboSwitch-2000 series (which includes the four-slot Mini Chassis
and the 20-slot Maxi Chassis) supports from eight to 120 LAN ports.
It accommodates Ethernet, token-ring, and FDDI (Fiber Distributed
Data Interface) support in the same chassis, and it also provides a
flexible management capability you can access via an RS-232
connection directly on the CPU module, an external terminal
connection, or the vendor's SNMP-compliant management ap
plication.
PRICE PER OVERALL
PORT TEST EVALUATION
VENDOR/MODEL CONFIGURATION SCORE
====================================================================
BEST NetWiz TurboSwitch-2000 $570 9.45
RUNNER-UP Fibronics GigaHub $739 8.54
VENDOR/MODEL PERFORMANCE FEATURES USABILITY
==============================================================================
BEST NetWiz TurboSwitch-2000 ***** **** ****
RUNNER-UP Fibronics GigaHub **** *** ****
BUFFER MAX. MAX.
SIZE PORTS MAC SWITCH-
PER PER ADDRESS/ ING
VENDOR/MODEL PORT SWITCH PORT
RATE
===============================================================================
BEST NetWiz TurboSwitch-2000 256 KB 120 64,000 10 million
RUNNER-UP Fibronics GigaHub 256 KB 72 1700 44,640
KEY
Ratings from 1 to 5: * is the lowest; ***** is the highest.
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Cut-Throughs
