Midterm P1

Network Edge

consists of hosts (clients & servers)

Access Networks, physical media

wired, wireless communication links

Network Core

Interconnected routers & Network of Networks

Frequency Division Multiplexing (FDM)

type of cable based access

different channels transmitted in different frequency bands

shared among users

Hybrid Fiber Coax (HFC)

type of cable based access
asymmetric transmission rates
network of cable, fiber attaches homes to ISP router
shared among users

Digital Subscriber Line (DSL)

type of cable based access
uses existing telephone line to provide internet access
is not shared among users; dedicated connected

Wireless Access Networks

shared wireless access network connects end system to router
types are WLANs & Mobile Cellular Networks (5G)

Enterprise Networks

consists of companies, universities etc
has a mix of wire, wireless link tech (Ethernet & WIFI)

Data Center Networks

high bandwidth links connect 100s to 1000s of servers together and to the Internet

Host

function: takes app message, breaks into packets, transmites packets into access network
Packet Transmission Delay = L (bits) / R (bits/sec)

Twisted Pair (TP)

type of physical media
made of two insulated copper wires

Coaxial Cable

type of physical media
two concentric copper conductors; bidirectional

Fiber Optic Cable

type of physical media
glass fiber carrying light pulses
high speed operation with low error rate
high speed operation with low error rate

Wireless Radio

type of physical media
signal carried in electromagnetic spectrum
prone to reflection ,obstruction of object, interference, spying

Radio Link Types

type of physical media
examples are terrestrial microwave, WLANs, Wide Area, Satellite.

Guided Media

signals propagate in solid media: copper, fiber, coax

Unguided Media

signals propagate freely

Key Network Core Functions

forwarding packets: move arriving packets to next output link
routing packets: global action of determining the path a packet will take from source to destination

Store and Forward

entire packets must entire the router before being forwarded

End-to-End Delay

the total delay from source to destination; 2L/R

Queue

when packets arrive faster than they can be serviced

FDM and TDM (circuit switch types)

Frequency Division Multiplexing: each call allocated its own band
Time Division Multiplexing: time divided into slots, transmits at max rate but only during its designated time

Packet vs Circuit Switching

packet switching allows more users to use the network
circuit switch is prone to queuing but great for "bursty data"

Traceroute

program that provides delay measure from source to router

Internet Protocol Stack

(Top) Application, Transport, Network, Link, Physical (Lower)

Application Layer

Supports Network Apps (IMAP, SMTP, HTTP)

Transport Layer

Process-Process data transfer (TCP, UDP)

Network Layer

Routes datagrams from source to destination

Link Layer

data transfer btwn neighboring network elements

Physical Layer

bits "on the wire"

Encapsulation

(Hl (Hn (Ht ( M ) ) ) )

Packet Sniffing

network interface reads/records all packets passing by

IP Spoofing

Injection of packet with false source address

Denial of Service (DoS)

attackers make resouces unavailable to legitimate traffic by overwhelming resource with fake bogus.

Line of Defense

Authentication, Confidentiality, Integrity Checks, Access Restrictions, Firewalls.

Malware

Enters host via a virus (passed by receiving/executing objects) or worm ( given by passively receiving object that gets itself executed )