Finals 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… Email

Architecture overview How email 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 emails? 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.

TCP TCP services

Byte-based sequence number and acks

Estimating TCP’s Round Trip Time Timeout

TCP Reliable Data Transfer Handling lost ACKs

Handling premature timeout

Use of Cumulative Acks

Fast Retransmit mechanism

TCP Flow Control Receiver advertising spare room in

receive window.

Sender limits unacked data to size of receive window

TCP Connection management 3-way Handshake

SYN, ACK, SYN-ACK sequence

Closing a connection FIN, ACK sequence

TCP Congestion Control (CC) Causes and costs of congestion End-to-end vs. Network Assisted CC Defining loss event Adjusting congestion window

1. AIMD2. Slow start3. Reaction to 3 duplicate ACKs4. Reaction to Timeout

Why treat 3 and 4 differently?

TCP FairnessDelay Modeling Definition of ‘fairness’ Why is TCP called ‘fair’ ? Impact of parallel TCP connections on

fairness.

TCP delay modeling with Slow Start Non-persistent HTTP Persistent pipelined HTTP Non-persistent HTTP with X parallel

connections

Chapter 4

Network Layer

Basic concepts Key network layer functions

Routing Forwarding Connection setup

in some networks like ATM

Routing vs. Forwarding

Distinction between services provided by Internet and ATM networks

Virtual Circuits Networks Vs. Datagram Networks Vs. Circuit-switched networks

Forwarding table Structure Maintenance

Switching mechanism

Signaling for VC setup

Datagram networks

Forwarding Table structure

Route Lookup mechanism Longest prefix matching Why Longest Prefix

Router Architecture Input port

Functions Switching Fabric

3-types of fabrics Memory, bus, crossbar Advantages/Disadvantages of each

Output port Queuing, Scheduling

Queue management Input vs Output port queuing

Head-of-the-line (HOL) Blocking.

Origins of congestion queuing delay and loss

IP datagram format

ver length

32 bits

data (variable length,typically a TCP

or UDP segment)

16-bit identifier

Internet checksum

time tolive

32 bit source IP address

IP protocol versionnumber

header length (bytes)

max numberremaining hops

(decremented at each router)

forfragmentation/reassembly

total datagramlength (bytes)

upper layer protocolto deliver payload to

head.len

type ofservice

“type” of data flgsfragment

offsetupper layer

32 bit destination IP address

Options (if any) E.g. timestamp,record routetaken, specifylist of routers to visit.

how much overhead with TCP?

20 bytes of TCP 20 bytes of IP = 40 bytes + app

layer overhead

Basic IP concepts Fragmentation and Reassembly

IP Addresses

Notion of subnets

CIDR addresses Why CIDR was adopted?

Hierarchical addressing Route aggregation

Network Address Translation How does it work?

Translation process Translation table

Uses of NAT Problems with NAT

ICMP, IPV6 ICMP

Use Location in protocol stack How does traceroute work?

IPV6 Main differences with IPv4 Transitioning from IPV4 to IPV6

Tunnelling

Routing Algorithms Routing problem : finding the least-

cost path

Global vs. decentralized routing Static vs. dynamic routing

Link state vs. distance vector routing

Link State Routing

Dijkstra’s algorithm

How does it work?

Why is it the same as breadth-first search

Distance Vector Routing Bellman-Ford Equation

Distance Vector Algorithm

Count-to-infinity problem Good news vs. bad news Poisoned reverse technique

Link State vs Distance Vector Message complexity Speed of convergence Robustness

Hierarchical Routing Autonomous systems

Scalability of routing

Administrative control

Inter vs Intra AS routing

Hot-potato routing

Routing Information Protocol (RIP) Distance Vector protocol

Routing Recovery from Failures Implementation

How ‘routed’ works

OSPF Link State routing

Djikstra’s algo

Route Advertisement exchange

Additional Features over RIP

Hierarchical OSPF

BGP Intra-AS routing

What BGP advertisements mean

Criteria for route selection Policy vs performance

Chapter 5

Data Link Layer

Data link layer services Framing Reliable delivery between adjacent

nodes Flow control Error detection Error correction Half vs full-duplex transmission

Error Detection As opposed to correction Parity checking

Single bit parity 2-Dimensional bit parity

CRC checksum Advantages How to compute

Multiple Access Protocols Resolving contention on shared

media Types

Channel Partitioning Random Access Taking turns

Channel Partitioning Protocols

Time Division Multiple Access (TDMA)

Frequency Division Multiple Access (FDMA)

Random Access MAC Protocols The problem of collision

Two components Detecting collisions Recovering from collisions

Aloha Slotted ALOHA Pure (unslotted) ALOHA

Comparison Synchronization effort Efficiency (how to compute?)

CSMA and CSMA/CD CSMA

Improvement over ALOHA Carrier Sensing before transmission

CSMA/CD Sensing + detection

Link-Layer Addressing MAC address structure

Each MAC address is globally unique

Address Resolution Protocol (ARP)

Routing across LANs How are MAC addresses in packets handled?

Ethernet Bus vs. Star topology

10BaseT vs 100BaseT vs Hubs vs Switches Why do we have distance restrictions on connected hosts? Hierarchical interconnections

With Hubs With Switches

Ethernet Frame Structure

Channel access protocol CSMA/CD Binary Exponential Backoff

Switches Self-configuration

Reverse Path Learning A.k.a backward learning A.k.a Transparent bridges

Learning and forwarding algorithms

Traffic isolation effect

Hubs vs. Switches vs. Routers

Point-to-point Protocol (PPP) one sender, one receiver, one link

PP design requirements Framing,bit transparency, error detection,

liveness, address negotiation

Data frame Byte Stuffing

To differentiate header bit pattern from payload bits

ATM Origins of ATM

Services provided by ATM

ATM Protocol Stack Functions of different layers

IP over ATM Why do we need it? How does it work?

MPLS Goals of MPLS

What’s different and what’s similay to ATM?

Why is it needed?