Lecture 3: Systems Engineering III EEN 112: Introduction to Electrical and Computer Engineering Professor Eric Rozier, 2/6/2013

COMBINING GATORS, GRADES, AND BOOLEAN ALGEBRA/LOGIC

How can we formalize how we solve these problems? Same rules as last time… – In Room I, if a grade is in the room, the sign will be true. If a gator is in the room, the sign will be false. – In Room II, the situation is the opposite.

The Grade and the Gator Q1 Room I Both rooms contain grades. Room II Both rooms contain grades.

The Grade and the Gator Q1 Room IRoom II A

ASSESSMENT

Pop Quiz Today Important notes – I will have this graded by Friday Morning – This quiz is correctable, up to full credit. If you get an answer wrong, when I hand it back you can correct it and submit it for regrading. – Use this to help test how well prepared you are for the exam’s section on boolean algebra and logic gates.

NETWORKING

How do machines talk to each other? TCP/IP – one of the main methods. – TCP – Transmission Control Protocol – IP – Internet Protocol Also called the DoD model due to ARPANET

ARPANET ARPANET – Advanced Research Projects Agency Network – Funded by ARPA and later DARPA – Connected research Universities and laboratories in the US

ARPANET The world’s first “packet switching” network – Groups all transmitted data, regardless of content, type, or structure, into suitably sized blocks called “packets”. – Packets are then routed through the network Circuit switching was the previous technology (like how corded phones used to work) – A limited number of dedicated point to point connections.

ARPANET Packet Switching – Based on designs by Baran, Davies, and Roberts of Lincoln Laboratory – More robust than circuit switching

ARPANET Packet Switching – Optimize utilization, link capacity – Minimize response times – Increase robustness

ARPANET 1971

ARPANET 1980

Internet Today

Anatomy of Internet Traffic Internet protocol suite Uses encapsulation to provide abstraction of protocols and services. Data is sent down the layers by an application. Layers near the top are logically closer to the application Layers near the bottom are logically closer to data transmission.

Anatomy of Internet Traffic

Application layer – Process to process – Same layer applications might use to talk on the same “host”. Transport layer – Host to host – The way two applications on different hosts but the same router might use.

Anatomy of Internet Traffic Internet layer – Used to exchange data across network boundaries – Host addressing and identification using IP addresses – Packet routing – how to get from source to destination

Anatomy of Internet Traffic

Link layer – Defines networking methods within the scope of a local area network on which hosts communicate without intervening routers, describes local topology. – MAC, VPNs, networking tunnels, etc

Internet Protocol IP address – Numerical label assigned to each device participating in a network – Identifies – a name is what we are looking for – Addresses – Indication of where what we are looking for is

Internet Protocol

Each of the four numbers is a set of 8 bits, or an octet Originally the were supposed to indicated network number (highest order octet), and host identifier with the rest

IP Address Problem How many IP addresses are possible with 32 bits? – About billion addresses – First exhaustion of a pool happened on Jan, 31, – Next pool exhaustion happened on April 15, – Only a few years until total exhaustion.

IPv6 32-bit examples are IPv4 IPv6 has 128 bits, or 16 octets How many more? – * 10^38

How do I get from a name to an address? First we contact a name server – Our router or gateway will have the information needed to contact a domain name server – They contain DNS records, such as: A records - address records NS records – name servers MX records – mail exchange etc

Domain Name Servers Domain names are divided up into zones – TLDs – top level domains.com,.net,.org,.edu,.us,.uk, etc Divide up their space into second level domains – Hierarchical

Domain Name Servers en.wikipedia.org – First we get a referral to.org’s TLD name server – TLD server for.org then tells us who to contact about wikipedia.org – This server will then tell us how to contact en.wikipedia.org In this case we are first told to chat with text.wikipedia.org which then gives us text.esams.wikipedia.org

Domain Name Servers Final resolution is a CNAME record, or canonical name, which will lead to an A record, or address

How this ends up working Imagine addressing a person in our class TLD might be UM Next level might be Stanford Next level might be 105 Finally, student X – X.105.stanford.um Address could be your position in the desks, and latitude and longitude.

Important note People aren’t telling us the route, just who to talk to in order to get the address – Robust! We can lose nodes in the route – Usually have many people to talk to in order to get an address

WRAP UP

Upcoming Items of Interest No lab next week Midterm I on Wednesday 2/13 – Boolean Algebra – Logic Gates – Networking