Wireless Networks.pptx
- 1. Wireless Networks Submitted by: Javaria(ADPCS-023A21-81) Anmol (ADPCS-023A21-24) Sameen(ADpcs-023A21-83) Ayesha(ADPCS-023R21-54) Muqadas(ADPCS-023A21-03) Submitted to: Dr. Ansar Munir Shah
- 2. Presentation Outline Wireless Technology overview The IEEE 802.11 WLAN Standards Secure Wireless LANs Migrating to Wireless LANs (Cutting the cord)
- 3. Wireless? A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier. The last link with the users is wireless, to give a network connection to all users in a building or campus. The backbone network usually uses cables
- 4. Common Topologies The wireless LAN connects to a wired LAN There is a need of an access point that bridges wireless LAN traffic into the wired LAN. The access point (AP) can also act as a repeater for wireless nodes, effectively doubling the maximum possible distance between nodes.
- 5. Common Topologies Complete Wireless Networks The physical size of the network is determined by the maximum reliable propagation range of the radio signals. Referred to as ad hoc networks Are self-organizing networks without any centralized control Suited for temporary situations such as meetings and conferences.
- 6. How do wireless LANs work? Wireless LANs operate in almost the same way as wired LANs, using the same networking protocols and supporting the most of the same applications.
- 7. How are WLANs Different? They use specialized physical and data link protocols They integrate into existing networks through access points which provide a bridging function They let you stay connected as you roam from one coverage area to another They have unique security considerations They have specific interoperability requirements They require different hardware They offer performance that differs from wired LANs.
- 8. Physical and Data Link Layers Physical Layer: The wireless NIC takes frames of data from the link layer, scrambles the data in a predetermined way, then uses the modified data stream to modulate a radio carrier signal. Data Link Layer: Uses Carriers-Sense-Multiple-Access with Collision Avoidance (CSMA/CA).
- 9. Integration With Existing Networks Wireless Access Points (APs) - a small device that bridges wireless traffic to your network. Most access points bridge wireless LANs into Ethernet networks, but Token-Ring options are available as well.
- 11. Roaming Users maintain a continuous connection as they roam from one physical area to another Mobile nodes automatically register with the new access point. Methods: DHCP, Mobile IP IEEE 802.11 standard does not address roaming, you may need to purchase equipment from one vendor if your users need to roam from one access point to another.
- 12. Security In theory, spread spectrum radio signals are inherently difficult to decipher without knowing the exact hopping sequences or direct sequence codes used The IEEE 802.11 standard specifies optional security called "Wired Equivalent Privacy" whose goal is that a wireless LAN offer privacy equivalent to that offered by a wired LAN. The standard also specifies optional authentication measures.
- 13. Hardware PC Card, either with integral antenna or with external antenna/RF module. ISA Card with external antenna connected by cable. Handheld terminals Access points
- 14. Hardware CISCO Aironet 350 series Wireless Handheld Terminal Semi Parabolic Antenna BreezeCOM AP
- 15. Performance 802.11a offers speeds with a theoretically maximum rate of 54Mbps in the 5 GHz band 802.11b offers speeds with a theoretically maximum rate of 11Mbps at in the 2.4 GHz spectrum band 802.11g is a new standard for data rates of up to a theoretical maximum of 54 Mbps at 2.4 GHz.
- 16. What is 802.11? A family of wireless LAN (WLAN) specifications developed by a working group at the Institute of Electrical and Electronic Engineers (IEEE) Defines standard for WLANs using the following four technologies ◦ Frequency Hopping Spread Spectrum (FHSS) ◦ Direct Sequence Spread Spectrum (DSSS) ◦ Infrared (IR) ◦ Orthogonal Frequency Division Multiplexing (OFDM) Versions: 802.11a, 802.11b, 802.11g, 802.11e, 802.11f, 802.11i
- 17. 802.11 - Transmission Most wireless LAN products operate in unlicensed radio bands ◦ 2.4 GHz is most popular ◦ Available in most parts of the world ◦ No need for user licensing Most wireless LANs use spread- spectrum radio ◦ Resistant to interference, secure ◦ Two popular methods Frequency Hopping (FH) Direct Sequence (DS)
- 18. Frequency Hopping Vs. Direct Sequence FH systems use a radio carrier that “hops” from frequency to frequency in a pattern known to both transmitter and receiver ◦ Easy to implement ◦ Resistance to noise ◦ Limited throughput (2-3 Mbps @ 2.4 GHz) DS systems use a carrier that remains fixed to a specific frequency band. The data signal is spread onto a much larger range of frequencies (at a much lower power level) using a specific encoding scheme. ◦ Much higher throughput than FH (11 Mbps) ◦ Better range ◦ Less resistant to noise (made up for by redundancy – it transmits at least 10 fully redundant copies of the original signal at the same time)
- 19. 802.11a Employs Orthogonal Frequency Division Multiplexing (OFDM) ◦ Offers higher bandwidth than that of 802.11b, DSSS (Direct Sequence Spread Spectrum) ◦ 802.11a MAC (Media Access Control) is same as 802.11b Operates in the 5 GHz range
- 20. 802.11a Advantages Ultra-high spectrum efficiency ◦ 5 GHz band is 300 MHz (vs. 83.5 MHz @ 2.4 GHz) ◦ More data can travel over a smaller amount of bandwidth High speed ◦ Up to 54 Mbps Less interference ◦ Fewer products using the frequency 2.4 GHz band shared by cordless phones, microwave ovens, Bluetooth, and WLANs
- 21. 802.11a Disadvantages Standards and Interoperability ◦ Standard not accepted worldwide ◦ No interoperability certification available for 802.11a products ◦ Not compatible or interoperable with 802.11b Legal issues ◦ License-free spectrum in 5 GHz band not available worldwide Market ◦ Beyond LAN-LAN bridging, there is limited interest for 5 GHz adoption
- 22. 802.11a Disadvantages Cost ◦ 2.4 GHz will still has >40% cost advantage Range ◦ At equivalent power, 5 GHz range will be ~50% of 2.4 GHz Power consumption ◦ Higher data rates and increased signal require more power OFDM is less power-efficient then DSSS
- 23. 802.11a Applications Building-to-building connections Video, audio conferencing/streaming video, and audio Large file transfers, such as engineering CAD drawings Faster Web access and browsing High worker density or high throughput scenarios ◦ Numerous PCs running graphics-intensive applications
- 24. 802.11a Vs. 802.11b 802.11a vs. 802.11b 802.11a 802.11b Raw data rates Up to 54 Mbps (54, 48, 36, 24,18, 12 and 6 Mbps) Up to 11 Mbps (11, 5.5, 2, and 1 Mbps) Range 50 Meters 100 Meters Bandwidth UNII and ISM (5 GHz range) ISM (2.4000— 2.4835 GHz range) Modulation OFDM technology DSSS technology
- 25. Authentication Means: Based on cryptography Non-cryptographic Both are identity-based verification mechanisms (devices request access based on the SSID – Service Set Identifier of the wireless network).
- 26. Data Integrity Data integrity is ensured by a simple encrypted version of CRC (Cyclic Redundant Check) Also vulnerable to some attacks
- 27. Security Problems Security features in Wireless products are frequently not enabled. Use of static WEP keys (keys are in use for a very long time). WEP does not provide key management. Cryptographic keys are short. No user authentication occurs – only devices are authenticated. A stolen device can access the network. Identity based systems are vulnerable. Packet integrity is poor.
- 28. Essential Questions Why is the organization considering wireless? Allows to clearly define requirements of the WLAN -> development plan How many users require mobility? What are the applications that will run over the WLAN? Helps to determine bandwidth requirements, a criteria to choose between available technologies. Wireless is a shared medium, not switched!!!
- 29. Choose the right technology Usually IEEE 802.11b or 802.11a 802.11b offers interoperability (WECA Wi-Fi Certification Program) 802.11a offers higher data rates (up to 54 mbps) -> higher throughput per user. Limited interoperability.
- 30. Data rates Data rates affect range 802.11b 1 to 11 Mbps in 4 increments 802.11a 6 to 54 Mbps in 7 increments The minimum data rate must be determined at design time Selecting only the highest data rate will require a greater number of APs to cover a specific area Compromise between data rates and overall system cost
- 31. Antenna Selection and Placement Permanently attached. Remote antennas connected using an antenna cable. Coax cable used for RF has a high signal loss, should not be mounted more than a 1 or 2 meters away from the device. Placement: consider building construction, ceiling height, obstacles, and aesthetics. Different materials (cement, steel) have different radio propagation characteristics.
- 32. Connecting to the Wired LAN Consider user mobility If users move between subnets, there are challenges to consider. OSes like Windows XP and 2000, Linux support DHCP to obtain the new IP address for the subnet. Certain applications such as VPN will fail. Solution: access points in a roaming area are on the same segment.
- 33. Vendor Information CISCO Systems Wireless http://www.cisco.com/warp/public/44/jump/wirel ess.shtml 3Com Wireless http://www.3com.com/products/en_US/prodlist.j sp?tab=cat&pathtype=purchase&cat=13&selcat =Wireless+Products Breeze Wireless Communications http://www.breezecom.com Lucent Technologies http://www.wavelan.com Symbol Technologies http://www.symbol.com
- 34. References CISCO Packet Magazine, 2nd Quarter 2002 http://www.cisco.com/en/US/about/ac123 /ac114/ac173/ac168/about_cisco_packet _issue_home.html 3Com University – Wireless LANs A Technology Overview www.3com.com/3comu National Institute of Standards and Technology Wireless Network Security http://csrc.nist.gov/publications/drafts/dra ft-sp800-48.pdf