Wednesday, October 29, 2014

Introduction to Networking Chapter 3 notes

Chapter 3 notes from Introduction to Networking
Network protocols and communication

Rather than adopt new standards and rebuilding the wheel, the network industry has developed a framework
-use of accepted models

All communication has 3 elements
-sender or source
-receiver or destination
-channel, the medium over which the message travels

transmission governed by protocols
-specific to type of communication

protocols necessary for effective communication
-specific to characteristics of communication method
-must be followed to be successfully delivered and understood
-identify sender and receiver
-common language and grammar
-speed and timing of delivery
-confirmation of acknowledgement requirements

Network protocols define
-message encoding
-msg formatting and encapsulation
-msg size
-msg timing
-msg delivery options

message encoding
-process of converting into another form for transmission

decoding - reverse of encoding; used to interpret

message formats
-depend on msg
-channel
if destination address and formatting wrong, then msg is not delivered
-computer format called a frame
frame acts like an envelope

message size
-large messages broken into smaller

message timing

access method- where you can send
flow control - how much and how fast
response timeout - reaction according to no answer

rules of communication

message delivery options
1 to 1 - unicast
1 to many - multicast
1 to all - broadcast

protocol suite - a group of interrelated protocols necessary to communicate

visualized as a stack

lower layers - transmit data
upper layers - focused on content


application protocol
transport protocol
internet protocol
network access protocol

standards organizations
-open standards encourage competition and innovation
-prevent monopoly 

-standards organizations write rules in order to maintain an open internet
-vendor neutral
-non-profit includes ISCO, IAB, IETF, IEEE, ISO

ISOC - promotes open development
     -evolution
     -world wide use

IAB - responsible for overall management
     -development of standards
     -oversight of architecture and protocols

IETF - develop, update maintain internet and TCP/IP technologies
     -produce RFC
IESO - technical management of the IETF
IRTF - focused on long term research
IEEE - wide range of standards
     -wireless
     -MAC for wired ethernet
ISO - created OSI model
EIA - electrical wiring, rack size
TIA - electrical wiring, cell tower, VOIP
ITU-T - video compression, IPTV, broad band communications, DSL
ICANN - coordinate  IP Address allocation
     -domain names used by DNS
     -TCP/UDP protocol/port number

IANA - handles ICANNs job of 
     -IP address allocation
     -domain name management
     -protocol identifiers

TCP/IP and OSI model

-layered model used to help visualize interaction between layers

benefits of layered model
-assists in protocol design
-fosters competition
-prevents different layer changes from affecting other layers
-provides common language for network functions/capabilites

Two types of model

protocol model - closely matches structure of a particular protocol suite
     -represents all functionality required to interface human network with data network

reference model - provides consistency within all types of networking protocols and services
     -describes the what, not the how

OSI model                    TCP/IP Model
-----------------------------------------------------
Application
Presentation               Application
Session
-----------------------------------------------------
Transport                       Transport
-----------------------------------------------------
Network                         Internet
-----------------------------------------------------
Data link
Physical                         Network access



OSI model designed by ISO
TCP/IP model deployed faster, so that it is what has been used

OSI model has specific functions at all layers

7.  Application Layer - means for end to end connectivity between individuals in the human network using data networks
6. Presentation layer - provides a common representation of the data transferred between application layer services
5.  Session Layer - Provides services to the presentation layer to organize its dialogs and to manage data exchange
4.  Transport Layer - defines services to segment, transfer, and reassemble the data for individual communications between the end devices
3. Network Layer - provides services to exchange individual pieces of data over network between end devices
2. Data Link Layer - method for exchanging data frames between devices over common media
1.  Physical Layer - Decribes mechanical, electrical, functional, and procedural means to activate, maintain, and deactivate physical connections for bit transmission to and from a network device

TCP/IP model (AKA Internet model)
defined by RFC
     -contains technical and organizational documents

Application - represents data to the user, plus encoding and decoding control
Transport - supports communication between diverse devices across diverse networks
Internet - determines best path through the network
Network Access - controls hardware devices and media that make up the network

TCP/IP model is described in terms by the OSI model
     -network access layer doesn't specify which protocols to use when transmitting
     -only describes hand off

Data Encapsulation
segmentation - divide data into smaller, manageable, chunks
benefits - many conversations interleaved on the network
     -increase reliability of the transmission
     -more complex

     multiplexing - interleaving the pieces as they traverse the media

data at any layer a PDU (protocol data unit)

data - application layer PDU
segment - transport layer PDU
packet - network layer PDU
frame - data link layer PDU
bits - physical layer PDU

data encapsulation - process of adding headers and trailers before transmission

deencapsulation - occurs at end devices

OSI model describes processes of encoding, formatting, segmenting, and encapsulating data for transmission over the network

network address - 
     -contains layer 3 information required to deliver IP packet from source to destination

L3 address has 2 parts 
     -network prefix
     -host part

     network prefix used by routers to forward packet to the proper network

     host part used by routers to forward packets to the proper network

     host part used by last router to deliver to final destination

a L3 IP packet contains 2 addresses: source, destination

Data link address
L2 physical address - used to deliver from one network interface to another network interface on the same network

on Ethernet, L2 physical address know as MAC or BIA (burned in address)
     -48 bits

How does a host find MAC address?
     uses ARP (address resolution protocol)
     1) sending host send ARP request; broadcast to entire LAN
     2) all devices examine the broadcast to see if it contains its own IP address
     3) destination IP address device responds with ARP reply.  ARP reply contains associated MAC address

Access remote network

     1) sender determines destination is not in network
     2) sends to default gateway
     3) repeats 1 & 2 until reach destination

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