1. 568A (cross over )
* white green
* green
* white orange
* blue
* orange
* white brown
* brown
2. 568B (straight thru )
* white orange
* orange
* white green
* blue
* white blue
* green
* white brown
* brown
Cross over cable - do not used a hub or switch
- attach to RJ45 plug using one standard and the other one second standard
Computer Network Devices
Network switch - is a computer networking device that connects network segments.
- is a marketing term rather than a technical one
- switches may operate at one or more OSI layers, including physical, datalink, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch, although use of the term is diminishing.
Network hub or repeater hub - is a device for connecting multiple twisted pair or fiber optic Ethernet devices together and thus making them act as a single network segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision.
Network repeater - connects two segments of your network cable. It retimes and regenerates the signals to proper amplitudes and sends them to the other segments. When talking about, ethernet topology, you are probably talking about using a hub as a repeater. Repeaters require a small amount of time to regenerate the signal. This can cause a propagation delay which can affect network communication when there are several repeaters in a row. Many network architectures limit the number of repeaters that can be used in a row. Repeaters work only at the physical layer of the OSI network model.
Network bridge - reads the outermost section of data on the data packet, to tell where the message is going. It reduces the traffic on other network segments, since it does not send all packets. Bridges can be programmed to reject packets from particular networks. Bridging occurs at the data link layer of the OSI model, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. In our case the bridge can read the ethernet data which gives the hardware address of the destination address, not the IP address. Bridges forward all broadcast messages. Only a special bridge called a translation bridge will allow two networks of different architectures to be connected. Bridges do not normally allow connection of networks with different architectures. The hardware address is also called the MAC (media access control) address. To determine the network segment a MAC address belongs to, bridges use one of:
- Transparent Bridging - They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on ethernet networks.
- Source route bridging - The source computer provides path information inside the packet. This is used on Token Ring networks.
Network brouter - function similar to a bridge for network transport protocols that are not routable, and will function as a router for routable protocols. It functions at the network and data link layers of the OSI network model.
Network operating system (NOS) - is software that controls a network and its message (e.g. packet) traffic and queues, controls access by multiple users to network resources such as files, and provides for certain administrative functions, including security.
Network operating system features may include:
- basic support for hardware ports
- security features such as authentication, authorization, login restrictions, and access control
- name services and directory services
- file, print, data storage, backup and replication services
- remote access
- system management
- network administration and auditing tools with graphic interfaces
- clustering capabilities
- fault tolerance and high availability
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