Review Layer 2 Technologies n Common LAN Technologies

Review - Layer 2 Technologies n Common LAN Technologies u Token Ring (IEEE 802. 5) u FDDI u CSMA/CD n (Ethernet & IEEE 802. 3) Network devices u NICs, Bridges, Switches u Segmentation, Microsegmentation n Network troubleshooting 1

n What are the bandwidths of Token Ring? u 4, n 16, and 100 Mbps. What are two types of Token Ring frames? u Data/command n and Token. What fields control priority? u Reservation field and Priority field, both within the Access Control byte. n Who is responsible for removing an information frame? u The sending station. 2

n What is early token release? u. A new token is released as soon as the transmission of a frame is completed. n Token Ring uses ______ encoding. u Differential n What are the media used by Token Ring? u STP n and UTP. What is an MSAU? u. A n Manchester. hub-like device to connect Token Ring stations. How does a Token Ring topology differ from an Ethernet topology? u Token Ring is deterministic; Ethernet is not. 3

n What organization(s) standardized FDDI? u ANSI, n Name the four FDDI specifications from the lowest to the highest! u PMD, n and later ISO. PHY, MAC, and SMT. FDDI uses the ______ logical topology. u Ring. n FDDI uses the ______ physical topology. u Dual n ring. What is FDDI’s speed? u 100 Mbps. 4

n What is FDDI’s Media Access Control strategy? u Token-passing. n Describe the two types of traffic defined by FDDI! u Synchronous - for stations requiring continuous transmission capability; Asynchronous - for other stations. n The ______ scheme is used for allocating bandwidth. u Distributed n bidding. Why is FDDI very reliable? u If part of one ring is damaged, the other ring can be used. 5

n What media are used by FDDI? u Fiber n Optic (Multimode and Single-mode). Based on their characteristics, what are each fiber type used for? u Multimode is used for intra-building connectivity; Single-mode is used for inter-building connectivity. n Name three advantages of Optical Fiber over copper wiring! u Security; Reliability; and Speed. 6

n FDDI uses the ______ encoding scheme. u 4 B/5 B. n Describe the two station classes of FDDI! u Class A, or Dual Attachment Stations (DAS), attach to both rings; Class B, or Single Attachment Stations (SAS), attach to only one ring using a concentrator. n What is the purpose of a concentrator? u To ensure that a failure, or power down, of any given SAS, does not interrupt the ring. 7

n What is the most widely used LAN technology? u Ethernet n and IEEE 802. 3. Who created Ethernet? u Xerox. n Who developed Ethernet II? u DIX n (Digital, Intel, Xerox). What is the LAN technology used by Ethernet and IEEE 802. 3? u CSMA/CD. n Who developed CSMA/CD? u The University of Hawaii. 8

n Is Ethernet II compatible with IEEE 802. 3? u Substantially n yes, with subtle differences. There are ____ varieties of Ethernet/IEEE 802. 3. u 18. n What is the relationship between an Ethernet II header and the header of an 802. 3 frame? u The n two headers have the same length. How does a NIC detect collision? u The amplitude of the signal on the networking media will increase. 9

n How does CSMA/CD handle a collision? u By backing off for a random period of time before retrying. n Why is Ethernet known as a best-effort delivery system? u If the destination must discard the data, then it does notify the source. n Describe three characteristics of 10 Base. T signals! u Use Manchester encoding; Combine both clock and data information into a selfsynchronizing stream; Designed to be sent and received over a segment that consists of 4 wires (two pairs). 10

n Ethernet uses the ______ logical topology. u Bus. n Ethernet uses the ______ physical topology. u Star. n How large an area can a hub covers? u. A n circle with a diameter of 200 m (radius of 100 m). What can be done if the area of the LAN is more than 200 meters in diameter? u. A repeater could be installed to extend the network. 11

n On a LAN, what part of the host connects to the media? u The n NIC. To function, a ______ builds a MAC address table. u Bridge. n How does a bridge improve network performance? u By eliminating unnecessary traffic and minimizing the chances of collisions. n A bridge filters traffic based on ______. u The station (MAC) address. 12

n A segment is ______. u. A section of a network bounded by routers, switches, or bridges. n In what situation will a bridge lower network performance? u When traffic between network segments becomes heavy. n What is a broadcast storm? u Too many broadcasts are sent out over the network. 13

n What is a multiport bridge? u. A n Switch. What is the similarity between bridges and switches? u Both use a table of MAC addresses to determine the segment on which a datagram needs to be transmitted, and reduce traffic. n How can a switch significantly reduce collisions? u By creating a dedicated virtual connection between two nodes who need to communicate. 14

n Why is moving to a switched LAN environment is very cost effective? u Existing n hardware and cabling can be reused. Why are switches significantly faster than bridges? u Switching is performed in hardware, while bridging is performed in software. n If each port of a switch can be thought as a microbridge, then segmenting using a switch can be thought as ______. u Microsegmentation. 15

n Can a router be used for segmentation? u Yes. n What is the difference between a router and a switch? u. A router base forwarding decisions on Layer 3 protocol address; A switch base forwarding decisions on Layer 2 protocol address. n Name some advantages of segmenting using routers! u Create smaller broadcast domains; Perform best path selection; Connect different networking media and different LAN technologies; Connect LANs running different protocols; Connect to WANs 16

n What is the best approach to network troubleshooting? u Start at layer 1, and progressively troubleshoot the higher layers. n Usually, troubleshooting internetworking devices is limited to layers ______. u 1, 2, and 3. 17

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