Network Devices Lecture 1

Review Topologies Physical Star Ring Dual Ring Bus Mesh Logical Token Ring Bus Media Twisted pair UTP STP Fiber RF Coax 10Base2 10Base5

NICs Identification – MAC address MAC – media access control 48 bit/6 byte/12 hexidecimal unique identifier First 6 hexidecimals identify the OUI – organizationally unique identifier – identifies the manufacturer of the NIC card Last 6 hexidecimals are the S/N of the device Example: 00-E0-B8-57-3D-DC 00-E0-B8 OUI 57-3D-DC S/N

NIC Considerations Network compatibility (Ethernet or TR) Bus compatibility PCI – peripheral component interconnect Newer computers or equipment 64-bit or 32-bit ISA – industry std. architecture – old Older computers or equipment Port compatibility Usu. Twisted pair; Multiple connector types is a combo card H/W compatibility With O/S

Laptop NICs PCMCIA - Personal Computer Memory Card International Association

Assuming this is a Ethernet/10BaseT network. How far apart can these computers be? 100 meters Peer to Peer Network

A hub would regenerate the signal. Ethernet Network Assume these computers are in different offices. Some are more than 100 meters apart. How will they be able to communicate?

Hub Multiport repeater Regenerates signals Receives signal on one port; sends signal out all other outgoing ports Extends the network because the signal has been regenerated. Usu. two types of ports MDI – medium dependent interface Uplink port MDI-X – medium dependent interface crossed Regular port (already crossed) Use straight-through cable to connect computer to hub Use cross-over cable to connect from MDI-X port to MDI-X port on a switch.

Ethernet Network YTC1 has a message to go to YTC3 YTC1 YTC2 YTC3 YTC4 Only YTC3 would pick up the message.

Frame Messages are broken into smaller pieces called frames for traversing the network. Header Address field Source & Destination MAC DataFCSTrailer

Bridge Network device that connects two segments of a network or two LANs. Receives a “frame” on one port. If the destination address on the frame is on another segment, it will forward the frame. Otherwise, it blocks the frame. Reduces traffic; therefore, collisions. Builds MAC tables of the devices on the segments connected to it. Largely replaced by Switches and Routers.

80/20 Rule 80% of the traffic should not cross the bridge. Only 20% of the traffic should be on the other side of the bridge.

Types of Bridges Transparent Bridges Invisible to other devices on the network. Blocking and Fowarding Most popular type of bridge Translational Bridges Connects two LANs running different protocols; for instance, Ethernet and TR Translates the data from one protocol to the other. Source-route Bridges Used in IBM Token Ring networks. Entire route from source to destination is embedded within the frame.

Switch Intelligent network device Multiport bridge Looks at destination MAC address of incoming frame and makes decision about whether to pick up the frame and if so, which port to forward the frame out. Peforms microsegmentation Breaks up collision domains

Switch – cont’d Provides full-duplex operation 100 Mbps would be 200 Mbps operation in full duplex because you can send and receive simultaneously at 100 Mbps Five processes Listening Learning Filtering Forwarding Blocking

Switching Methods Cut-through (FastForward) Reads the destination address and forwards No error checking Fastest Store and Forward Receives the entire frame before forwarding Performs basic error checking Most error free form of switching Fragment-free After receiving first 64 bytes, forwards frame. A collision fragment is less than 64 bytes.

Twisted Pair Cables Straight-through cable Allows you to connect “unlike” devices or “like” devices that have a port that has a crossed connection. Cross-over cable Allows you to connect “like” devices.