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23 Cards in this Set
- Front
- Back
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NIC (Network Interface Card) Components
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Includes a unique data link layer address (called a MAC address), placed in them by their manufacturer
Includes a socket allowing computers to be connected to the network Organizes data into frames and then sends them out on the network |
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NIC
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Network Interface Card - Contains physical and data link layer protocols
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Network Cable Types
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-Untwisted wire pairs (UTP) – leading LAN cable type
-Shielded twisted pair (STP) -Coaxial cable – heavy, not flexible -Optical fiber – high capacity |
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Hubs
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-Act as junction box linker
-Sold w/ 4, 8, 16 or 24 ports -Can connect various cable types, such as UTP and coax. -Repeat (reconstruct and strengthen) incoming signals -Extends LAN segment distance |
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NOS
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Network Operating System:
-Enables servers to operate -Performs data link, network, and application layer functions -Acts as the application software by executing and responding to the requests sent to them by clients -Optimized |
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NOS Directory Service
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-Information on LAN resources
-Active Directory Service (ADS), or Domain Name Server (DNS) -Resources organized into a tree, each branch contains a domain (a group of resources) A domain has a server (domain controller) -Responsible for resolving address information -Responsible for managing authorization -Uses Lightweight Directory Acess Protocol (LDAP) to interact with client computers |
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Ethernet (IEEE 802.3)
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-Used by almost all LANs today
-Developed by: Digital Equipment Corp., Intel and Xerox |
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Logical Topology
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-How the network works conceptually
-Like a logical data flow diagram (DFD) or -Like a logical entity relation diagram (ERD) |
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Physical Topology
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-How network is physically installed
-Like physical DFD or physical ERD |
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MAC (Media Access Control)
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-Contention-based protocol called CSMA/CD (Carrier Sense Multiple Access / Collision Detect)
-Frames can be sent by two computers on the same network at the same time -They will collide and become garbled -Can be termed as “ordered chaos” -Tolerates, rather than avoids, collisions |
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CSMA/CD
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Carrier Sense (CS):
Listen to the bus to see if another computer is transmitting before sending anything Transmit when no one is transmitting Multiple Access (MA): All computers have access to the network medium Collision Detect (CD): Declared when any signal other than its own detected If a collision is detected To avoid a collision, wait a random amount of time and then resend message |
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Swithced Ethernet Topology
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Uses switches (not hubs)
Support small # of computers -Group of point-to-point circuits -No sharing of circuits -Logical and physical topology becomes a star via switch -Reads destination address of frame and sends to specific port |
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Modes of Swith Operations
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-Cut through switching
-Store and forward switching -Fragment free switching |
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Cut through switching
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-Read destination address and start transmitting
-Without waiting for the entire message is received -Low latency; but may waste capacity (errorred messages) -Only on the same speed incoming and outgoing circuits |
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Store and forward switching
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-Wait until the whole message is received, perform error control, and then transmit it
-Less wasted capacity; slower network -Circuit speeds may be different |
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Fragment free switching
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-Read the first 64 byte segment (contains the header)
-Perform error check, if it is okay then start transmitting -Compromise between previous two modes |
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Shared Ethernet 802.3
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Capable of using about only 50% of capacity (10BaseT) before collisions become a problem
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Switched Ethernet
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Runs at up to 90% capacity on 100Base-T
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Finding Network Bottlenecks
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Check the server utilization during poor performance
-If high >60%, then the server is the bottleneck -If low <40%, then the network circuit is the bottleneck -If between 40% - 60%, both the server and circuits are the bottlenecks |
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Improve Server Performance-HW
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-Add a second server
-Upgrade the server’s CPU -Increase its memory space -Add more hard disks -Add a second NIC to the server |
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Improve Network Perormance-SW
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-Choose a faster NOS
-Fine tune network and NOS parameters such as --Amount of memory used for disk cache --Number of simultaneously open files --Amount of buffer space |
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Improve Network Performance-disk
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-Disk reads are the slowest task the server needs to do
-Consider Redundant Array of Inexpensive Disks (RAID) --Improve performance and increase reliability |
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LAN Performance Strategies
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Increase Server Performance
Increase Circuit Capacity Reduce Network Demand |
