Cisco 776 - 776 Router - EN Manual de usuario descargar pdf (Pagina 5)

Multiple Destination

Networks

An ISDN router that supports

multiple destination networks has

the ability to connect to separate

remote destinations simul-

taneously by monitoring LAN

traffic and bringing up channels

to remote networks based on the

destination addresses of the

packets. 3Com’s LAN Modem,

Cisco’s 776 and NETGEAR

RT328 offer support for

multiple destination networks

(see figure 1); however, the

3Com LAN Modem and RT328

are the only routers that provide

configuration for multiple desti-

nations through the GUI. The

3Com LAN Modem was the

only device that supports data

call bumping, which is the

ability to tear down one of two

ISDN B channels that are con-

nected to a single destination for

re-direction. See figure 3.

Application

Throughput (3Com

LAN Modem)

The Tolly Group benchmarked

application throughput only on

the 3Com LAN Modem in

order to measure performance

from the user’s experience.

Due to time constraints, rival

products were not bench-

marked for performance. Test

results show that, regardless of

data type, the 3Com LAN

Modem delivers aggregate

application throughput of over

120 Kbit/s for unidirectional

traffic and over 200 Kbit/s for

bidirectional traffic. Appli-

cation throughput was

measured with NAT enabled,

suggesting that 3Com’s NAT

implementation does not

impose a processing penalty.

With compression enabled, the

3Com LAN Modem’s effective

throughput for data traffic

increased up to 80%. Using

pre-compressed data and com-

pression enabled, the 3Com

LAN Modem delivered

throughput that was within 3%

of the throughput achieved

with compression disabled.

For compressible text data, the

3Com LAN Modem delivered

a maximum throughput of 184

Kbit/s for uploads, 224 Kbit/s

for downloads and 329 Kbit/s

for bidirectional traffic. For

pre-compressed data, the 3Com

LAN Modem delivered a maxi-

mum throughput of 121 Kbit/s

for uploads, 122 Kbit/s for

downloads and 207 Kbit/s for

bidirectional traffic. See

figures 4 and 5.

Analysis

Applications

Supported Via NAT

A router that uses NAT effec-

tively hides all internal IP

addresses from the Internet and

re-maps them to a single IP

address dynamically assigned

to it by the ISP. All packets

forwarded by the ISDN router

to the external network appear

to come from a single IP

address (even though there

may be multiple stations

behind the router). NAT is a

cost-saving feature because all

© 1999 The Tolly Group Page 5

The Tolly Group 3Com Corp. OfficeConnect LAN Modem

121.0

122.3

207.1

118.8

122.3

204.3

0

50

100

150

200

250

Upload Download Bidirectional

Throughput (Kbit/s)

Compression Disabled Compression Enabled

Source: The Tolly Group, April 1999

Figure 5

TCP/IP Application Throughput,

Pre-Compressed Data with NAT Enabled

3Com LAN Modem Connected to a Central Office

Ascend MAX 1800 via Two 64 Kbit/s ISDN B Channels

1 2 3 4 5 6 7 8

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