Midterm Review

Chapter 1

Internet Concepts Applications, End-hosts, Routers, Switches, Communication Links Overall architecture How they are organized Network edge vs network core Circuit-switching vs packet switching FDM vs TDM Datagram vs Virtual Circuit network Both are forms of Packet switching Statistical Multiplexing

Internet Concepts … What is a protocol Definition Examples 5 Layers of TCP/IP protocol stack 7 Layers of OSI protocol stack Encapsulation of packets

Types of Services Connection-oriented vs Connectionless service Reliable vs unreliable service Byte-stream vs datagram delivery Flow-control vs Congestion Control In-order vs out-of-order (rather any-order) delivery Quality-of-service vs best-effort delivery Performance requirements: Bandwidth, Delay, Data loss rate

Types of delay Queuing delay Transmission delay Propagation delay Their formulas Numerical problems Should be able to solve, if you understand the basic concepts

Chapter 2

Application Architectures Client-Server model Pure peer-to-peer model Hybrid peer-to-peer model Differences between them Examples of each

Addressing IP address Binary vs Dotted decimal representation Conversion between the two Port numbers Reserved vs unreserved ports

Sockets Definition Components of a socket What constitutes a socket? What constitutes a connection? Half-association vs full-association

Application layer protocols HTTP General view of the architecture HTTP servers design Persistent vs. non-persistent HTTP Persistent HTTP with and without pipelining Don ’ t worry about memorizing syntax of protocol messages But understand how the protocol works

Application layer protocols … FTP Protocol overview Control vs Data connection Why do we need two connections

Application layer protocols … Architecture overview How gets from one place to another Difference between mailbox and message queues Protocol overview SMTP, POP3, IMAP, HTTP How they differ SMTP vs. HTTP Push vs Pull architecture Why is it so easy to send SPAM s? What is the main drawback of current architecture that lets this happen?

Domain Name System Overview What does it do? How it works? Why is it not centralized? Root vs TLD vs Authoritative vs Local DNS servers What ’ s the hierarchy? Where does Local DNS server belong?

Domain Name System … Iterative vs recursive queries Pros and cons of each DNS caching – how it helps? Types of DNS records How to insert new records into DNS

Socket API Sequence of Socket API calls At client and at server For TCP and for UDP How do you specify a server ’ s port number How does a client get a port number?

Chapter 3

Transport layer overview What does it do? Importance of sockets Importance of port numbers Reliable vs. unreliable delivery Multiplexing and demultiplexing

UDP Why is it needed at all? How is a UDP socket identified Is it a half or a full association? UDP header components Demultiplexing in UDP Using single UDP socket to talk to multiple remote machines.

TCP What services does it provide? How is a TCP connection identified Is it a half or a full association? TCP header components Demultiplexing in TCP Using single UDP socket to talk to multiple remote machines.

Detecting errors Checksum What does it mean? Does a correct checksum mean no errors? How is it computed?

Reliable data transfers Concept of Finite State Machines States, Events, transitions, actions Simple FSMs for Stop-and-Wait protocol at sender/receiver With no errors With bit errors With packet losses

Pipelined RDT Protocols Go-back-N Selective Repeat Sender/Receiver algorithms Relationship between window size and sequence number range.