3.2.3 S
WITCH
C
ASCADING
Theoretically, the switch partitions the collision domain for each port in switch cascading so that you may
up-link an unlimited number of switches. In practice, the network extension (cascading levels and overall
diameter) must comply with the IEEE 802.3/802.3u/802.3z and other 802.1 series protocol specifications,
which limit the timing requirement from physical signals defined by the Media Access Control (MAC) and
PHY802.3 series specification, and timer from some OSI layer 2 protocols such as 802.1d, 802.1q, and LACP.
The fiber, TP cables, and devices’ bit-time (round-trip) delay are as described in Table 3-1.
Table 3-1. Cable’s bit-time (round-trip) delay.
1000BASE-X TP, Fiber
100BASE-TX TP
100BASE-FX Fiber
Round-Trip Delay: 4096
Round-Trip Delay: 512
Cat. 5 TP Wire: 11.12/m
Fiber Cable: 10.10/m
Bit Time Unit: 1 ns
(1 sec./1000 Mega bit)
Cat. 5 TP Wire: 1.12/m Fiber Cable: 1.0/m
TP to Fiber Converter: 56 kbps
Bit Time Unit: 0.01 ms (1 sec./100 Mega bit)
The sum of all elements’ bit-time delay and the overall bit-time delay of wires/devices must be within the
bit-time (round-trip) delay in a half-duplex network segment (collision domain). For full-duplex operation, this
will not apply. Use the TP-Fiber module to extend the TP node distance over fiber optic cable and to provide
the long-haul connection.
Typical Network Topology in Deployment
A hierarchical network with minimum switch levels may reduce the timing delay between the server and the
client station. This approach will minimize the number of switches in any one path. It will also lower the
network loop possibility and will improve network efficiency. If more than two switches are connected in the
same network, select one switch as the Level 1 switch and connect all other switches to it at Level 2. We
recommend that you connect a server/host to the Level 1 switch.
Example 1: Same LAN.
All switch ports are in the same local area network. Every port can access each other (see Figure 3-2).
Figure 3-2. No VLAN configuration.
CHAPTER 3: Installation
12
8-Port 1000BASE-TX Web-Smart
Ethernet Switch with 2 SFP Dual Media Ports
8-Port 1000BASE-TX Web-Smart
Ethernet Switch with 2 SFP Dual Media Ports
