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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