ConnectGear gs-1124 用户指南

 

The maximum length of the extension is equal to the quantity (slotTime - 

minFrameSize). The MAC continues to monitor the medium for collisions while it is 
transmitting extension bits, and it will treat any collision that occurs after the 
threshold (slotTime) as a late collision. 

 

The switch is a layer 2 Ethernet Switch equipped with 24 Fast Ethernet ports 

and 2 optional modules which support Gigabit Ethernet or 100M Ethernet. Each port 
on it is an independent LAN segment and thus has 26 LAN segments and 26 
collision domains, contrast to the traditional shared Ethernet HUB in which all ports 
share the same media and use the same collision domain and thus limit the 
bandwidth utilization. With switch’s separated collision domain, it can extend the 
LAN diameter farther than the shared HUB does and highly improve the efficiency 
of the traffic transmission. 

Due to the architecture, the switch can provide full-duplex operation to 

double the bandwidth per port and many other features, such as VLAN, bandwidth 
aggregation and so on, not able to be supported in a shared hub. 

 

 

Terminology 

Separate Access Domains:

As per the description in the section of “What’s the Ethernet”, Ethernet 

utilizes CSMA/CD to arbitrate who can transmit data to the station(s) attached in the 
LAN. When more than one station transmits data within the same slot time, the 
signals will collide, referred to as collision. The arbitrator will arbitrate who should 
gain the media. The arbitrator is a distributed mechanism in which all stations 
contend to gain the media. Please refer to “What’s the Ethernet” for more details. 

In Fig.3-5, assumed in half duplex, you will see some ports of the switch are 

linked to a shared HUB, which connects many hosts, and some ports just are 
individually linked to a single host. The hosts attached to a shared hub will be in the 
same collision domain, separated by the switch, and use CSMA/CD rule. For the 
host directly attached to the switch, because no other host(s) joins the traffic 
contention, hence it will not be affected by CSMA/CD. These LAN segments are 
separated in different access domains by the switch.

  

Micro-segmentation: 

To have a port of the switch connected to a single host is referred to as 

micro-segmentation. It has the following interesting characteristics. 

- 

There is no need the access contention (e.g.Collision). They 
have their own access domain. But, collision still could happen 
between the host and the switch port. 

- 

When performing the full duplex, the collision vanishes. 

- 

The host owns a dedicated bandwidth of the port. 

The switch port can run at different speed, such as 10Mbps, 100Mbps or 

1000Mbps. A shared hub cannot afford this.