8
Note:
Even though the connector is shielded, either unshielded or shielded cables
and wiring may be used.
2.
Connect the other end of the cable to the corresponding device.
3.
Use the LINK LED to ensure proper connectivity by noting that the LED will be illumi-
nated when the unit is powered and proper connection is established. For port 8, if the
LINK LED is not illuminated, change the setting of the up-link switch. If this does not
help, ensure that the cable is connected properly and that the device on the other end
is powered and is not defec
tive.
2.3 Powering the hubs
The dual-speed hubs incorporates an internal universal power supply, and has a recessed
male IEC connector for the AC power cord in the rear. A 230Vac 50Hz power cord is sup-
plied with each unit.
The auto-ranging power supply supports installation environments where the ac voltage is
from 90 to 260 volts with an input frequency between 47 and 63Hz, and consumes a max-
imum of 20 watts. In order to power down the unit, simply unplug either end of the ac power
cable.
3.0 Operation
This chapter describes the function and operation of the dual-speed hubs.
3.1 Dual-speed functionality
The hubs handle the two different traffic domains separately (unless it is stacked with a
DS8-B). The DS8-B provides switched (bridged) connectivity between the ethernet
(10Mbps) and Fast ethernet (100Mbps) domains. It joins the two network domains for uni-
fied operation, and filters/forwards packets in both directions to maximise bandwidth util-
isation and performance. There is no software set-up to be done at installation or for main-
tenance.
Each time a packet is received on one domain of the bridge module, the decision is taken
to either filter or forward the packet. Error packets are always filtered. For good packets,
the filter and forward decisions are based on the destination address contained in each
packet. If the destination address is on the same domain from which the packet originated,
then it is filtered and not forwarded to the other domain. If the destination address is not
found to be a match in the address table for the originating domain, then it is forwarded to
the other domain. If it is a new node address coming in which the switch did not previous-
ly know about, it “learns” the new address and puts it in the correct port address table. See
“address learning” for more details.
This diagram below shows the filter/forward logic for both domains.
100Mb/s Domain : 100Mb/s packets are
forwarded when the destination address is
NOT
in the 100Mb/s domain address table
10Mb/s Domain : 10Mb/s packets are
forwarded when the destination address is
NOT
in the 10Mb/s domain address table
100Mb/s Domain : 100Mb/s packets are
forwarded when the destination address is
IS
in the 100Mb/s domain address table
10Mb/s Domain : 10Mb/s packets are
forwarded when the destination address is
IS
in the 10Mb/s domain address table
10
100
A
B
C
10771
10771
5
The bridge operates in the store-and-forward mode which filters out bad packets and
maintains optimum performance in both domains. Packet forwarding delay is only 5µs
(plus packet time), much less than traditional store-and-forward bridge products enabling
the hubs to maintain high network performance. The bridge has 8K node address capac-
ity., suitable for use in large networks. Addresses are self-learning so that filtering/for-
warding of 10mbps and of 100Mbps packets is maintained correctly even when users
move their connection or change speed, or power down.
The DS8-B bridge module is implemented as a daughter board. The hub has an LED on
the front labelled ‘BR’ that will be ‘ON’ when the module is installed internally.
Note:
Only one DS8 hub is allowed per repeater stack.
1.6 Up-link switch for cascading
The hubs have up-link switch for port 8, located on the front of the hub. It enables the ports
cable to either connect to a user station (= position) or to be cascaded to another hub (X
position) (see section 4.4 for more details about up-link). Like all ports, port 8 is a dual-
speed port which will sense the speed of the connected device. The up-link switch oper-
ates the same, whether port 8 is connected to either 10Mbps or 10Mbps devices.
When the up-link port is used to cascade two hubs or stacks together, the auto-sensing
feature will cause the connecting link to operate at 100Mbps speed.
1.7 Applications
Example 1:
A DS8-B hub serves a small office with mixed speed requirements. Some users operate at
100Mbps and some users and utility devices (such as print servers) run at 10Mbps. All share
the same hub, and talk to each other via the bridge module inside. Any node can change
speed at any time without affecting network operation or impacting other users.
Example 2:
Where there are existing 10Mbps hubs and users, they can easily be cascaded into any port
of the DS8-B. This allows simple plug-and-play addition of 100Mbps ports to an existing
10Mbps network without having to change it. Nodes that are capable of 100Mbps speed can
be moved to any dual-speed port, and will automatically operate at the higher speed. The
dual-speed ports on the DS8-B can be used for adding 100Mbps users or for accommodating
existing high performance users. The 100Mbps traffic does not use the bandwidth of the
10Mbps domain, so overall performance of the network is improved.
1
10
100
100
LK
RX
ACT
COL
PWR BR
UPLINK
2
3
4
5
6
7
8
A
B
C
E
D
A. 100 Server
B. 100 Users
C. 10 Users
D. Print server
E. Router
A. 10Mbps domain
B. 10 BUS 100
C. 10 BUS 10
Figure 3
Figure 6
