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Tonight’s plan:

  1. Annotated Bib
  2. Review network plan assignment
  3. Writing in APA
  4. Panko Ch. 2: Network Standards
  5. Panko Ch. 3: Physical Layer

Annotated Bibliography

For APA style, Mark digs The Owl at Purdue as well.

For the assignment:

  • five good references
    • good generally means academic; you can use white papers, popular press, etc., but you need to make a good case for using them (validate their quality)
    • a sentence or two will suffice for validation
  • Mark is going to show us the APA module in Word, but Dan Lehmann mentions Zotero, a free bib program that runs as a Firefox extension! It has integration with Word, OpenOffice, WordPress… holy cow! Pardon me while I step out and download!
  • A sen

Review — Network Plan

Recall how in the assignment we’re running wires under the carpet. Dr. Moran really, really discourages that solution. Maybe for a week. Maybe.

One print server is preferable.

Assignment didn’t cover disaster recovery. Some students recommended having two servers backing each other up. Otherwise, one server is probably plenty.

Prices ranged from $12K to $40K. Dr. Moran recommends $10K server.

Ooooh! Command Prompt!

  • Remember, you can get your physical address (MAC — Media Access Control) via ipconfig /all. Print that screen, hang on to it. That MAC address is stamped into your system. If someone swipes and uses your laptop, you (or the police) can track your computer down online with that MAC.
  • Network not working? ping! Just like Red October (Dr. Moran said that).
  • ping your own network card: ping 127.0.0.1. Of course, this doesn’t tell you much, as the ping doesn’t actually go out onto the network and look back.
  • Some companies turn off responses to pings to avoid ping attacks.
  • tracert: trace route! see how many routers are between you and your destination
  • nslookup: tells you what server and IP address you are on. Remember: nslookup is a program, so when you enter nslookup at the command prompt, you run that until you type “exit”.
  • netstat: shows open connections/ports!

Don’t forget: four ways to identify computer on network:

  1. MAC address
  2. IP address
  3. name
  4. port (216 = 65536 ports available!)

This is like 1543 Turks conquer Constantinople! Keys to the kingdom (or, in this case, the final exam)!

Now, on to Chapter 2: Network Standards

TCP numbers the packets (message order)

HTTP has its own way of doing things, doesn’t care about order.

TCP supervisory messages are pure headers.

Reliability is our focus:

  1. Transfer Control Protocol (TCP) is reliable, meaning it guarantees delivery or tells you what happened
  2. User Datagram Protocol (UDP) is not reliable but is used for VoIP, video.

Transfer Control Protocol

  1. receiver acknolwedges each correctlyt received TCP segment (which increases Internet traffic)
  2. if acknowledgment is not received by the sender, the sender retransmits the TCP message (which also increases traffic)
  3. connection-oriented

User Datagram Protocol

  1. Connectionless protocol
  2. much traffic on DSU network uses UDP, since there’s so much peer-to-peer traffic

Connection-oriented protocols (TCP) have to have formal openings and closings: that’s also part of the higher traffic level. Advantages: guaranteed delivery, messages can refer to earlier messages by number. Disadvantage: “expensive” (uses bandwidth)

Connectionless protocols (HTTP, UDP) simply send messages without prior connection and without subsequent connection closings.

Old seven-layer architecture (OSI: Other Standards Interconnect. Mnemonic: All People Seem To Need Diet Pepsi):

  1. Application
  2. Presentation
  3. Session
  4. Transport
  5. Network
  6. Data link
  7. Physical

But now it’s condensed to five layers, in Hybrid TCP/IP-OSI architecture:

  1. Application
  2. Transport
  3. Internet
  4. Datalink
  5. Physical

TCP/IP suite includes dozens of apps: World Wide Web, e-mail, FTP,…

Physical addresses — MAC addresses — do not change (unless we’re being naughty). IP addresses can change.

IP addresses come in four octets (four 8-bit chunks… a.k.a. 4 bytes)

Ethernet Frame runs on MAC addresses, which means they can be switched, since MAC addresses don’t change.

Ethernet does not guarantee delivery, so it’s not reliable in this fun network sense of the word. If Ethernet transmits data and that data gets lost, it does not get retransmitted. Ethernet is (basically) connectionless. This is why Ethernet networks are overprovisioned: to provide lots of extra bandwidth so packets don’t collide and get lost.

IP packet includes source and destination packets. Also a TTL: “time to live” expiration date!

TCP vs. UDP: expect to explain the difference on the final!

Why not make all layers reliable? It’s expensive!

Error correction at the transport level: why good?

  1. Only two transport processes: one on source host, one on destination host.
  2. Error correction only necessary once, saving cost.

Not all apps need reliability:

  1. VoIP can’t wait for error correction
  2. network mgmt protocols must place as low a burden on network as possible

Source and destination hosts have five layers. Switches have two layers. Routers have three layers.

Other Major Standards Architectures

  • IPX/SPX: used by Novell Netware file servers (another victim of Microsoft; Novell once ran on 90% of network servers)
  • SNA (Systems Network Architecture): used by IBM mainframes
  • AppleTalk: how Macs used to talk to Mac servers, a little peer-to-peer, small network app

Chapter 3: Physical Layer Propagation

DSU: mostly copper cable! But every building has a fiber optic connection to the central hub in the Science Center.

Copper is all electronic pulses, 12-volt range between 3 and 15, direct current, limited to 100 meters. (Coaxial can go 180 m.) Fiber optic uses pulses of light. Network cards make the magical conversion of packets to binary pulses of whatever.

Panko says we should know binary (“think in binary… think in Russian!”). MAC address is 48-bit (6 octets). IP address is 32-bit now, but IPv6 will be 128-bit. IPv4 gives us just 4.3B (232) addresses. IPv6 gives us 3.4×1038 (2128) addresses.

Stranded wire more physically flexible, but also has more errors. Dr. Moran prefers solid wire.

TIA/EIA-568 standard governs Unshielded Twisted Pair (UTP) wiring. In Europe, ISO/IEC 11801. 8 wires, 4 pairs: orange and green used for communication. Wires 1, 2, 3, and 6 are the conducting wires. RJ-45 (RJ stands for Regular Jack) for networks, RJ-11 for phones. BNC is old TV coaxial cable.

UTP cable cheap! $60 gets you 1000 feet. Relatively rugged, easy to work with, dominates media for access links (80% of connections). Fiber is a pain to work with.

Attenuation: fading with distance

Noise: random energy.

Noise floor: average noise level.

Noise spikes: natural fluctuations; disrupt transmission when >=signal

UTP cords are like big radio antennae: they pick up all those signals from lights, blenders, etc. Shielded wires avoid that!

We twist those wires to avoid crosstalk interference. Leaving big untwisted lengths at ends makes that crosstalk interference worse!

Category 5 wire standard: max speed 1 Gbps over 100 m. There are some faster standards in copper (Cat 6 & 7), but they haven’t gained acceptance yet; we pretty much go to fiber above Cat 5.

Fiber: don’t point it in your eye! Multi-mode won’t hurt (cheaper, uses LED), but single mode shoots laser!

Multimode: 8.3-62.5 micron diameter glass, lights bounce around inside; limited to a few hundred meters

Single mode might run 40 km. There’s a big booster at Prairie Junction (north side) to get the signal from Madison to I-29, then another run down to Sioux Falls.

Radio Propagation: Wireless Networks!

Omnidirectional antennae: <100m.

Chicken wire blocks radio! Build a straw bale house, stucco it, and you’re screwed! The iron in the quartzite in our old DSU buildings also blocks wireless. 802.11b-g can be blocked by cordless phones (that’s our problem!). Moisture also attentuates radio waves.

Network topology:

Star is most common (DSU uses extended star, each building has its own switch; has a B IP license; SDSU only has C license; we have ltos more numbers!)

Mesh: more connections

Ring (not on tonight’s agenda)

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