Ethernet Interface Configuration; Introduction - Nokia ESB26 User Manual

5. Ethernet Interface Configuration

Introduction

The ESB26 switch supports simultaneous, parallel conversations between Ethernet segments.
Switched connections between Ethernet segments last only for the duration of the packet.
New connections can be made between different segments for the next packet.
The ESB26 solves congestion problems caused by high-bandwidth devices and a large
number of users by assigning each device to its own 100 or 1000 Mbps segment.
Because the major bottleneck in Ethernet networks is usually due to collisions, an effective
solution is full-duplex communication, an option for each port on the switches (note that
Gigabit Ethernet ports also support half duplex). Normally, Ethernet operates in half-duplex
mode, which means that stations can either receive or transmit. In full-duplex mode, two
stations can transmit and receive at the same time. When packets can flow in both directions
simultaneously, the effective Ethernet bandwidth is 200 Mbps for Fast Ethernet ports and
2 Gbps for Gigabit Ethernet ports.
Switching Frames between Segments
Each Ethernet port on the switch can connect to a single workstation or server, or to a hub
through which workstations or servers connect to the network.
When stations on different ports need to communicate, the switch forwards frames from one
port to the other at wire-speed to ensure that each session receives the full available
bandwidth.
To switch frames between ports efficiently, the switch maintains an address table. When a
frame enters the switch, it associates the Media Access Control (MAC) address of the sending
station with the port on which it was received.
Building the Address Table
The switch builds the address table by using the source address of the frames received. When
the switch receives a frame for a destination address not yet listed in its address table, it floods
the frame to all ports of the same virtual LAN (VLAN) except for the port that received the
frame. When the destination station replies, the switch adds its relevant source address and
port ID to the address table. The switch then forwards subsequent frames to a single port
without flooding them to all ports.
The address table can store up to 16K address entries without flooding any entries. The switch
uses an aging mechanism, defined by a configurable aging timer, so that if an address remains
inactive for a specified number of seconds, it is removed from the address table.
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