networks introduction Flashcards by Maryam Sonnie

hosts

millions of connected computing devices, hosts = end systems running on network applications

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communication links

physical infrastructure - fibre, copper, radio, satelite

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what is bandwidth

transmission rate

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what do packet switches do?

forward packets

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what do protocols generally do

control sending and receiving of messages

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name 2 internet standards

RFC - request for comments

IETF - internet engineering task force

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RFC

REQUEST FOR COMMENTS

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IETC

INTERNET ENGINEERING TASK FORCE

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what is a protocol

define format and order of messages sent and received amongst network entities and actions taken on message transmission receipt

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name some pieces that make up a network

hosts, routers, links of various media, applications, protocols, hardware, software

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what does a network layer do in general

each layer implements a service via its own internal-layer actions, relying on services provided by the layer below

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why is layering used?

Because we’re dealing with complex systems

explicit structure allows identification relationship of complex system pieces
modularization eases maintenance and updating of system

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how does modularization ease maintenance and make updating a system easier?

change of implementation of a layer’s service is transparent to the rest of the system - e.g change in gate procedure doesnt affect how the rest of the system operates

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List the 7 layers in the ISO/OSI reference model

application
presentation
session
transport
network
link
physical

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purpose of application layer

supporting network application. Focused on end-to-end, App-App and device-device

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presentation layer purpose

allows applications to interpret the meanings of data - how data/info is presented to the user

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What is the session layer

devices - src and dest need to synchronize and be at the same point to ensure that data is not missed - synchronization, checkpointing, recovery of data

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Transport layer purpose

process to process data transfer

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network layer purpose

routing of datagrams from src to dest

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link layer purpose

transfer between neighboring network elements

physical layer purpose

encoded bits on the physical architecture

which layers can be embeded into the application layer?

app, pres, session

Which layers occur in the Internet protocol stack and TCP/IP suite? give examples of some protocols that exist in these layers

Application - ftp, http, smtp
transport - tcp, udp
network - ip, routing protocols
link - ethernet, wifi (802.111)
physical

Explain the process of encapsulating in a network

message - gets new header at each layer (encoded). Fro m src travels down layers and get put into layer packet each time, then passed back up layers moving along physical and link layers

LAN

Local area network - interconnect hosts up to a few or maybe a few tens of km apart

MAN

metropolitan area network - connects devices up to a few hundred km apart

WAN

wide area network - interconnect hosts that are all over the world

Unicast

info sent from one sender to one receiver

Anycast

Info delivered to any one receiver that is part of a particular set

Multicast

info sent to set of receipients

broadcast

info sent to all nodes that are part of a particular network

network edge

hosts: client-server - where end devices reside in

Where are servers located

often in data centers

access networks/physical media

wired, wireless communication links, allow edge to connect to the internet

what is the network core

inter connected routers - network of networks | allows movement of traffic between the src and dest

how does the network core work?

through packet switching: hosts break application layer messesages into packets packets are then forwarded from one router to the next, across links on path from source to destination

routing

determines src-dest path

forwarding

move packets from router input to router output

Describe the internet's structure

network of networks End systems connect to internet via access ISPs Access ISPs are inter connected

how not to connect ISPs. Why?

have each ISP link to every other ISP in the world- doesnt scale - O(N^2) connections

Discuss connecting each ISP to one global ISP - drawbacks

monopoly | not possible - others will see what a viable business it is and join in - will never just have 1 global isp

problem with multiple global isp that are not connected

fragmented internet

What is an IXP

Internet exchange point - ISPs come together - physical inter connection point because there is traffic that needs to be transfered between ISPs

Purpose of a regional network

connect access networks to ISPs

what if there was no regional network?

unnecessary hops - e.g.) cape town to global to jhb instead of just cpt to jhb

what is the purpose of content provider networks

not aimed at providing internet access - instead, they run their own networks to bring their content closer to where the end users are - e..g google will push content to different servers in different parts of the world - content nodes

Tier 1 ISP

have global reach - nodes in major cities - connect to them and be able to access everyhting

What are content provider networks and what do they do? part2

private network that connects data centers to internet - often bypassing tier 1 and regional ISPs