Computer Network Diagrams

"Logical topology, or signal topology, is the arrangement of devices on a computer network and how they communicate with one another. How devices are connected to the network through the actual cables that transmit data, or the physical structure of the network, is called the physical topology. Physical topology defines how the systems are physically connected. It represents the physical layout of the devices on the network. The logical topology defines how the systems communicate across the physical topologies.
Logical topologies are bound to network protocols and describe how data is moved across the network. ...
EXAMPLE : twisted pair Ethernet is a logical bus topology in a physical star topology layout. while IBM's token ring is a logical ring topology, it is physically set up in star topology." [Logical topology. Wikipedia]
This Cisco logical computer network diagram example was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Cisco Network Diagrams solution from the Computer and Networks area of ConceptDraw Solution Park.

"There are two definitions for wireless LAN roaming:
Internal Roaming (1): The Mobile Station (MS) moves from one access point (AP) to another AP within a home network because the signal strength is too weak. An authentication server (RADIUS) performs the re-authentication of MS via 802.1x (e.g. with PEAP). The billing of QoS is in the home network. A Mobile Station roaming from one access point to another often interrupts the flow of data among the Mobile Station and an application connected to the network. The Mobile Station, for instance, periodically monitors the presence of alternative access points (ones that will provide a better connection). At some point, based on proprietary mechanisms, the Mobile Station decides to re-associate with an access point having a stronger wireless signal. The Mobile Station, however, may lose a connection with an access point before associating with another access point. In order to provide reliable connections with applications, the Mobile Station must generally include software that provides session persistence.
External Roaming (2): The MS (client) moves into a WLAN of another Wireless Internet Service Provider (WISP) and takes their services (Hotspot). The user can independently of his home network use another foreign network, if this is open for visitors. There must be special authentication and billing systems for mobile services in a foreign network." [Wireless LAN. Wikipedia]
This Cisco roaming wireless local area network diagram example was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Cisco Network Diagrams solution from the Computer and Networks area of ConceptDraw Solution Park.