Claude Shannon made many contributions to the field of computer science including the Master’s thesis that related Boolean algebra to circuit design, a Ph.D. thesis that founded information theory and the Ultimate Machine.
log2(1 + SNR)
where B is bandwidth and SNR is the signal to noise
ratio, the ratio of the power of the signal to the power of the noise.
Also, see the Wikipedia article on Differential Manchester.
4B 5B from the patent.
Framing is used in many point-to-point protocols.
The Wikipedia page lists the bits.
PPP is specified in RFC 1661.
In the dark ages, PPP connections would be run over modems to connect to the Internet.
HDLC is based on IBM’s SDLC. Once it was widely use to connect mainframes. It is part of the System Network Architecture (SNA) protocol family which was largely developed in Research Triangle Park.
Bit stuffing is used in many serial link protocols. It is easy to implement, but is does make the transmission speed a little unpredictable.
I hope we did parity in CSCI 255.
The IP checksum is computed so frequently that it may be written in assembly language.
The Cyclic Redundancy Check (CRC) is based on polynomial rings with coefficients over the Galois Field of order 2. The error-correcting properties of particular CRC polynomials can be proven using techniques from abstract algebra.
CRC-8 is x8 + x2 + x + 1.
x8 + x2 + x + 1 = (x + 1) (x7 + x6 + x5 + x4 + x2 + 1)
Polynomials like these are also used to encrypt cell phone conversations.
TCP déjà vu. Go to slide 78.
20 years since the mid-1970s? Go to slide 88.
It’s still pretty much the same address and frame format.
This was in the old days of the shared cable. Matt’s Tech Projects has a page building a 10base5 “thick Ethernet” network with a lot of pictures.
Now go to slide 106.
Since wireless links “share” a common media, they must be strictly controlled.
The actress Hedy Lamarr and composer George Antheil patented spread spectrum frequency hoping in 1941. They proposed using a piano rolls to synchronize transmission over 88 frequencies. The Navy wasn’t interested for a couple of decades.
CDMA uses a chipping code.
Someone must have taken my notebook’s antennae.
802.11 is a large set of standards. The Wi-Fi Alliance certifies Wi-Fi® implementations.
Oops... Someone got the wrong figure in the slide. It should be Figure 2.31, where B can reach A and C, and C can reach B and D, but A cannot reach D.
The picture is on slide 122 and slide 120.
- IEEE 802.11 protocols
- Hotel Wi-Fi
- Hotel Wi-Fi blocking
- IEEE 802.1X
- supplicant – client device (or sometimes the software in the device)
- authenticator – network device (access point of Ethernet switch)
- authentication server – RADIUS or EAP
- SSID – service set identifier or wireless network name
- WPA2 and IEEE 802.11i & IEEE standard
- EAP – Extensible Authentication Protocol
- Basics of Digital Certificates and Certificate Authority
- best Wi-Fi router?
- WPS (Wi-Fi Protected Setup) brute force vulnerability
- Wi-Fi on planes opens door to in-flight hacking, warns US watchdog
- GAO report on air traffic control