1. CS4500CS4500 Dr. ClincyLecture1 Ch3: Underlying Technologies (2 of 3) Lecture #4 Finish LANs and start Pt-to-Pt WANs

2. CS4500CS4500 Dr. ClincyLecture2 Ethernet implementation Each device on an Ethernet network has a NIC (network interface card) Contains the physical address –ah ha, this is how I can change locations and still get emails Some implementations of Ethernet: 10BASE5 (thick ethernet) 10BASE2 (thin ethernet) 10BASE-T (twisted pair) 10BASE-FL (fiber link) Ethernet addressing: Unicast Multicast Broadcast Connects host to medium and perform CSMA/CD British naval connector or bayonet nut connector – for coaxial cable

3. CS4500CS4500 Dr. ClincyLecture3 Ethernet implementation

4. CS4500CS4500 Dr. ClincyLecture4 Ethernet implementation Unshielded twisted pair

5. CS4500CS4500 Dr. ClincyLecture5 Ethernet implementation

6. CS4500CS4500 Dr. ClincyLecture6 Fast Ethernet implementation 100 Mbps Ethernet 2-wire type (100BASE-TX or 100BASE-FX) 4-wire type (only 100BASE-T4) To make faster, collision domain was decreased 10 fold (250 meters vs 2500 meters) How did they go from 10Mbps to 100Mbps – collision domain

7. CS4500CS4500 Dr. ClincyLecture7 Fast Ethernet implementation

8. CS4500CS4500 Dr. ClincyLecture8 Fast Ethernet implementation

9. CS4500CS4500 Dr. ClincyLecture9 Gigabit Ethernet implementation Need for data rates higher than 100 Mbps resulted in a 1000 Mbps Ethernet called gigabit Ethernet Again, we had the choice to either decrease the collision domain or increase the minimum frame size Because 25 meters for the 100 Mbps Ethernet was short enough, the minimum frame size was increased to get the desired speed Another option is to do away with the CSMA/CD overhead by connecting every station to the hub using 2 separate paths (this will do away with collisions) – called full-duplex Ethernet (can still have half-duplex)

10. CS4500CS4500 Dr. ClincyLecture10 Gigabit Ethernet implementation

11. CS4500CS4500 Dr. ClincyLecture11 Ten-Gigabit Ethernet implementation No half-duplex at all – only full duplex

12. CS4500CS4500 Dr. ClincyLecture12 Token Ring LAN Token Ring is a protocol defined by IEEE 802.5 Use a token passing ACCESS method Token Passing Method During idle times (network not being used), a token circulates The token is passed station to station until a station needs to send data When the station sends it’s data, it holds the token The data (or frame) circulates and get re-generated by each station The Rx takes in and COPY the frame (based on destination address) The data then continues back to the original Tx Token is then release to circulate

13. CS4500CS4500 Dr. ClincyLecture13 Token Ring layers Uses the same layers as Ethernet (MAC and LLC) LLC Layer – logical link control layer – performs the error and flow control routines (same as Ethernet) MAC Layer – media access control layer –it implements the Token Passing Access Method (versus Ethernet’s CSMA/CD access method) Token Ring

14. CS4500CS4500 Dr. ClincyLecture14 Token Ring Data frame Token Ring frame defines 3 types of frames: data, token and abort Data Frame – carries a protocol data unit (actual data) and is addressed to a specific Rx (not broadcasted) Token Frame – is the placeholder frame (token) and uses only 3 of the 9 fields (SD, AC and ED) Abort Frame – doesn’t carry any info and is used to stop transmission SD – start delimiter – alert and synch the Rx AC – Access control - 3 bits set priority, 1 bit tells what type of frame, 1 bit is a monitor bit tells which station is monitoring or sending at the time, and 3 reservation bits for station wishing for access FC – Frame control – 1 bit tells if PDU is control info or data, 7 bits is used by Token Ring (ie. tells how to use AC field info) DA – Destination address SA – Source Address Data CRC – cyclic redundancy check – error checking ED – end delimiter – signals end of data FS – frame status – intermediate stations can set it letting the Tx know they read it, Rx can set it letting the Tx know it was copied and can be discarded now

15. CS4500CS4500 Dr. ClincyLecture15 Token Ring Implementation Token Ring is a series of shielded twisted pair transport medium linking each station into a ring Because the token needs to pass through each station with in the ring, if a station is down, it could be a problem Therefore, for each station, a switch is used to by pass the down (or disabled) station These bypass switches are packaged together as a MAU – multi-station access unit NOTE: As we covered last lecture, don’t confuse the Ring Token technology with the Ring topology. With a ring topology approach, you would want to traverse in either direction (this is the main benefit of a ring topology) – explain Ethernet in ring topology.

16. CS4500CS4500 Dr. ClincyLecture16 FDDI Ring FDDI stands for Fiber Distributed Data Interconnect Data rate is the same as Fast Ethernet (100 Mbps) Light signals versus electrical signals are used Uses a token passing access method with self- healing What do we mean by “self healing” ? Ability to detect and fix problems. The hardware automatically recognizes and fix problems

17. CS4500CS4500 Dr. ClincyLecture17 FDDI Ring How does the “self-healing” works ? Two independent rings connecting all stations are used – dual counter-rotating rings The second ring is used only if a failure occurs Functions like a Token Ring LAN until a failure (ie. fiber cut, node failure) In this case, the intermediate (non-Rx) nodes keep copies of the sent frame too

18. CS4500CS4500 Dr. ClincyLecture18 FDDI Ring When the station detects it can’t communicate with the adjacent station, it uses the second ring to bypass the adjacent station Given a fiber cut or node failure, this station is bypassed and the ring is closed

19. CS4500CS4500 Dr. ClincyLecture19 FDDI Frame

20. CS4500CS4500 Dr. ClincyLecture20 WIRELESS LANS Wireless communication is one of the fastest growing technologies. The demand for connecting devices without the use of cables is increasing everywhere. Wireless LANs can be found on college campuses, in office buildings, and in many public areas. In this section, we concentrate on two wireless technologies for LANs: 1)IEEE 802.11 wireless LANs, sometimes called wireless Ethernet, 2)and Bluetooth, a technology for small wireless LANs.

21. CS4500CS4500 Dr. ClincyLecture21 Wireless Transmission (not in book) Wireless devices can transmit signals using radio frequency narrow band, infrared waves and radio frequency spread spectrum. The frequency spread spectrum technique is typically used for internet applications Two types of frequency spread spectrum techniques: (1) FHSS- Frequency Hopping Spread Spectrum and (2) DSSS – Direct Sequence Spread Spectrum

22. CS4500CS4500 Dr. ClincyLecture22 FHSS- Frequency Hopping Spread Spectrum (not in book) Tx transmits at different carrier frequencies for the same period of time (rotates between a set of frequencies) The required bandwidth must be N times the original bandwidth, where N is the number of different carrier frequencies Tx and Rx must agree to the hopping pattern. In this case, the first bit signal is transmitted in spectrum 2.01-2.02Ghz, 2 nd bit transmitted in the 2.03-2.04 Ghz spectrum, 3 rd bit transmitted in the 2.04-2.05 GHz spectrum, etc.. Good technique for security reasons – if someone tunes to one of the 5 frequency spectrums below, they would only get 1/5 of the info being transmitted.

23. CS4500CS4500 Dr. ClincyLecture23 DSSS – Direct Sequence Spread Spectrum (not in book) Each bit sent by the Tx is replaced with a set of bits called a “chip code” For the time it takes to send the original single bit, it now will take more time to send the chip code Therefore, the data rate must be N times the original data rate, where N is the # of bits of the chip code Also, the bandwidth for the chip code should N times greater than the original bit stream’s BW Example of original bits being transmitted as 6-bit chip codes

24. CS4500CS4500 Dr. ClincyLecture24 ISM bands (not in book) In 1985, the FCC modified the radio spectrum to allow unlicensed devices (operating at 1 watt or less) to ISM bands – Industrial, Scientific and Medical bands Stimulated growth in wireless technology

25. CS4500CS4500 Dr. ClincyLecture25 Wireless LANs Architecture IEEE 802.11 covers 2 services – (1) BSS - Basic service set and (2) ESS – Extended service set BSS – is the base architecture for a wireless LAN – it contains a stationary or mobile stations and a central access point (optional) Without central access point, the BSS can’t transmit to other BSS’s example ?

26. CS4500CS4500 Dr. ClincyLecture26 Wireless LANs Architecture - ESS Contains 2 or more BSS’s with central access points The BBS’s central access points are connected via a distribution system (could be a wired LAN) – this network is called an Infrastructure network BBS’s within reach of one another can communicate BBS’s not within reach have to communicate via the central access points

27. CS4500CS4500 Dr. ClincyLecture27 Wireless LANs Access Method Wireless LANs use an access method similar to CSMA/CD access method discussed last lecture The access method is called CSMA/CA (vs CSMA/CD) and stands for carrier sense multiple access with collision avoidance With CSMA/CA, all nodes have equal access and the medium is sensed before data is sent However, collision detection is not applicable because the environment is wireless – THEREFORE, COLLISIONS MUST BE AVOIDED. CSMA/CA Process Each station determines how long it needs the medium and all other stations refrain from using it After the Tx detects the medium is free, it sends a RTS (request to send) and it contains the amount of time The Rx acknowledges the request by issuing a CTS (clear to send) to all stations Tx sends data Rx acknowledges the receipt of data Example

28. CS4500CS4500 Dr. ClincyLecture28 CSMA/CA and NAV The way collisions are prevented is: when the Tx issues a RTS, a timer called Network Allocation Vector (NAV) is created for the duration of time for (1) to (4) above – all stations affected by this transmission uses the NAV in letting it know when it can check the channel for idleness If free, Tx waits amount of time called distributed interframe space (DIFS) After Rx receive RTS, it waits amount of time called short interframe space (SIFS), before send a CTS

29. CS4500CS4500 Dr. ClincyLecture29 Bluetooth Wireless LAN technology designed to: –connect devices of different functions (ie phone, camera, printer, etc) –spontaneously form (devices find each other) –connect to the Internet –be small by nature – large size will cause chaos –Handle data rate of 1 Mbps with 2.4 GHz of bandwidth –Could incur interference between 802.11b wireless LAN and Bluetooth LANS (802.15) The networks are called “Piconet” Defined by standard 802.15 (PAN)

30. CS4500CS4500 Dr. ClincyLecture30 Bluetooth Architectures (2 types) Can have up to 8 stations One station is the primary and the rest are secondary stations all secondary stations synch their clock to the primary station. The communications with the primary can be 1-to-1 or 1-to-many Can have an unused 8 th secondary – must be activated to use and some existing secondary must be deactivated Multiple piconets combined is a Scatternet A secondary station in one piconet can be a primary station in a 2 nd Piconet

31. CS4500CS4500 Dr. ClincyLecture31 Completing coverage of LAN technologies

32. CS4500CS4500 Dr. ClincyLecture32 Internet – Underlying Technologies Recall the various types of interconnected networks comprising the Internet: LANs, Point-to-Point WANs and Switched WANs We have covered LANS: Ethernet, Token Ring, Wireless and FDDI Ring Let’s cover the Point-to-Point WANs Point-to-Point WANS Connect devices via a public network line (ie. telephone company) Telephone company – physical layer Point-to-Point WAN – data link layer and up Company services provided to make the connection: Modem (modem to switching station to ISP) DSL Cable Modem T Lines (ie. T1, T3) SONET (optical carriers)

33. CS4500CS4500 Dr. ClincyLecture33 Telephony/56K Modem Sampled 8000 times per sec with 8 bits per sample (1 bit for control) = 56 kps Digital Signal Analog Signal Digital Data

34. CS4500CS4500 Dr. ClincyLecture34 P-to-P: DSL – Digital Subscriber Line DSL – a set of technologies used to provide high-speed data service over copper wires that connect between the central office and local residences/businesses without expensive repeaters. How is DSL implemented ? – high-speed DIGITAL WAN between COs – link between subscriber and the network is analog (becoming more and more digital though) How does DSL work ? – divides the given bandwidth into 3 bands and offer phone service on one band and up and down stream traffic on the other 2 – phone service can occur with NO interruptions. What does POTS stands for ?? Ranges changed for 4th Book Ed

35. CS4500CS4500 Dr. ClincyLecture35 P-to-P: Other DSL Services RADSL – rate adaptive asymmetric DSL – scales back the speed of ADSL based on the quality of the wire and distance between the CO and user. Side Note: A newer version of ADSL called Universal ADSL (or UADSL) is being deployed in an attempt to standardize ADSL to a set of standard speeds – speeds vary across the Country HDSL – high bit rate DSL – an digital alternative to T-1 analog service (T-1 contains multiple high-speed analog lines) SDSL – symmetric DSL – same as HDSL however only 1 line is provided (is full-duplex) VDSL – very high bit rate DSL – similar to ADSL however, in addition to using twisted-pair, coaxial and fiber-optic can be used in getting a much higher bit rate

36. CS4500CS4500 Dr. ClincyLecture36 P-to-P: Cable Modem Still talking about point-to-point WANS Uses the cable TV network How does it work ?. some of the bandwidth dedicated to television signals is used for data traffic. How does it work ?. The data signals are modulated into sine waves and placed on analog channels How does it work ?. Typically, the BW in a neighborhood (or certain proximity) is shared (like a LAN in an office). Therefore, you never know if you have access to all of the BW. The more people using cable modems the worst the performance. Some cable companies can dedicate some BW for phone service therefore offering voice, video/TV and data services on one cable Cable modems are faster than computer modems because they are not limited by the 3000 Hz BW of the telephone line The newer cable systems uses digital cable boxes and digital networks can send/receive data on separate digital channels (draw picture of typical cable/video network – briefly explain history)