Copyright 2003 Factors that Impact Network Performance Network traffic (congestion). Multitasking desktop operating systems (Windows, UNIX, and Mac) allow simultaneous network transactions. Faster desktop operating systems (Windows, UNIX, and Mac) can initiate faster network activity. Increased number of client/server applications using shared network data.
Copyright 2003 Ethernet Performance of a shared-medium Ethernet/802.3 LANs is negatively affected by factors such as the following: –The broadcast delivery nature of Ethernet. –Carrier sense multiple access collision detect (CSMA/CD) access method allows only one host to transmit at a time. –Multimedia applications with higher bandwidth demand such as video and the Internet. –The latency of additional devices added by the extension of LANs by using repeaters. –The distance added by using Layer 1 repeaters.
Copyright 2003 Network Latency Latency, or delay, is the time a frame or a packet takes to travel from the source station to the final destination.
Copyright 2003 Ethernet 10BASE-T Transmission Times Bit time (or slot time) The basic unit of time in which 1 bit can be sent. For electronic or optical devices to recognize a binary 1 or 0, there is a minimum duration during which the bit is "on" or "off. " Transmission time Equals the number of bits being sent times the bit time for a given technology. Another way to think about transmission time is as the time it takes a frame to actually be transmitted. (Small frames take a shorter amount of time, large frames take a longer amount of time to be transmitted.)
Copyright 2003 Symmetric and Asymmetric Switching
Copyright 2003 Memory Buffering Port-based memory buffering –Packets are stored in queues that are linked to specific incoming ports. –It is possible for a single packet to block all other packets because its destination port is busy (even if the other packets could be delivered). Shared-memory buffering –All packets use a common memory buffer. –Packets in the buffer are then linked (mapped) dynamically to the appropriate destination port. –Helps balance between 10- and 100-Mbps ports.
Copyright 2003 Microsegmentation A switch employs microsegmentation to reduce the collision domain on a LAN. The switch does this by creating dedicated network segments, or point-to-point connections.
Copyright 2003 Switches and Collision Domains The network area where frames originate and collide is called the collision domain. All shared media environments are collision domains.
Copyright 2003 Switches and Broadcast Domains Broadcasting is when one transmitter tries to reach all the receivers in the network. The server station sends out one message, and everyone on that segment receives the message.
Copyright 2003 Communication Between Switches and Workstations