Internet - Power Point files

greydullNetworking and Communications

Oct 30, 2013 (3 years and 9 months ago)

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The

Internet

Internet Tiers


Internet is built in layers


9 Tier One computing centers in US


Many Tier Two providers connected to
Tier Ones


Lots of Tier Threes connected to Tier
Twos


If one link breaks, there are other routes
from A to B

TCP/IP


The language of the Internet


Provides many services


Hypertext Transport Protocol (HTTP) is
one service, FTP is another


We connect to Internet using TCP/IP
through Internet Service Providers (ISPs)

Dial
-
up Connections


Hardware: Modem or ISDN Terminal
Adapter


Software: Microsoft’s Dial
-
up Networking
(DUN)


Uses PPP


Point to Point Protocol (your
point to another modem)

Modems


Modulator/Demodulator: to convert digital
signals to analog to run over phone lines

UARTs


Universal Asynchronous
Receiver/Transmitter


Converts parallel data to serial data to
parallel data


External

modems do not have UARTs
(they use serial port, which has UART)


Internal

modems have on
-
board UART


16550A is today’s UART

BAUD


Technically, it is one cycle per second
(same as Hertz)


Max baud rate over phone lines (actually
phone switches) is 2400 baud


It’s 56 Kbps, not 56 baud or 56 K baud


33.6 Modem is 14 bits x 2400 Baud


Standards


V.90 is 56K down and 33.6 up


V.92 is 56K down and 48 upload


All of this over perfect phone
wires and to an equal modem on
the other end


FCC limit is 54Kbps


Best actual use is 48K down and
28K up (I get 32K max.)

Server

Me

Flow Control


Also called Handshaking.


Local flow control between modem and
COM port


Software uses special characters;
XON/XOFF; slower mode


Hardware uses extra wires; RTS/CTS


End
-
to
-
end flow control is between
modems which is handled by the modems

Connections


Internal


ACR (Advanced Commication Riser)


AMD


CNR (Communications Network Riser)


Intel


PCI slot


PCI
-
e slot


External


Serial port


USB port

Dial
-
up Networking


Network and Internet Connections applet


Will need to know ISP phone number,
account name and password


Use Point
-
to
-
Point Protocol (PPP)


Make sure there is dial tone on line in use


Make sure dial tone is plugged into Line
port


“No Carrier Detect(ed)” is no connection to
a modem on the other end

ISDN


Integrated Services Digital Network


Up to 64 Kbps by going digital all the way
to your house over Bearer (B) channel


D channels carry setup and configuration
at 16Kbps


Can get two B channels for 128Kbps in
Basic Rate Interface (BRI)


Can get 23 B’s and a D for 1.544Mbps


T1



xDSL


Asynchronous (ADSL) is 2Mbps down and 128
-
768
Kbps up


Synchronous (SDSL) has same up and down speed


but costs


Connect filters on all jacks except the one to DSL
modem


NIC setup is usually just DHCP now


Have to be within two miles of CO

2M

56K

2 miles

Cable


RG
-
6 or RG
-
59 cable to modem; RJ
-
45
connector and UTP to computer (CAT 5e)


6
-
100 Mbps down and 1
-
10 Mbps up


Got a bad rap at first due to many people
sharing a cable; fiber optic backbone now

Networking Revisited


The “language” of the Internet is TCP/IP.


Have to have an IP address


“Upstream” of you is likely a router that
hands out IP address when your modem is
turned on


DHCP can supply much more than just IP
address

Satellite


Used to require a dial
-
up modem for
upload traffic


Dish now handles both up and down


In theory, allows you to be way out in the
bush and still connect


500 Kbps down and ~50Kbps up

Routers


Lots to choose from at Fry’s


Provide firewall between you and Internet


NAT


Network Address Translation:
private IP’s inside and one IP outside
(public)

Connection Sharing


Internet Connection Sharing


allows
sharing of (dial
-
up) connection


Broadband (DSL and Cable): use router
between modem and PCs


XP’s (Internet Connection) Firewall can
prevent peer
-
to
-
peer networking as can
third party firewalls

isp

modem

router

pc1

pc2

pc3

WWW


World Wide Web


Runs on port 80


Servers run special software (IIS)

Internet Explorer


Internet Options in Control Panel or Tools menu in
Explorer


Internet Options has no effect outside of IE


General tab: home page, browsing history, searching


Security tab: Zones for Internet, local intranet, trusted
sites and restricted sites


Privacy tab: Cookies and pop
-
ups


Content tab: What will or will not display


Connections tab: Set up connection to Internet, connect
to VPN, proxy server


Programs tab: Settings for browser and add
-
ons


Advanced tab: Accessibility, browsing, international and
security



Proxy Server


A LinkSys router operates at Layer 3 of
OSI model (Network layer)


PS operates at layer 7


Application layer


You request the PS to request a web page

Email


Email address: <name>@<server>


Need account name, password, POP3
server name and SMTP server name


Should come from your ISP


Have to use your ISP’s outgoing mail
(SMTP) server


even for other accounts


Get a “throw away” account (free) at
Yahoo or Hot Mail or Google


Ports: POP3=110; IMAP=143; SMTP=25


FTP


File Transfer Protocol


Ports 20 and 21


You use FTP to download my PowerPoint
decks; I use it to upload decks


User name and password sent in clear
text; don’t use important password


Telnet and SSH


Telnet to remotely control a server/router


Clear text, again


Port 23


SSH = Secure Shell; port 22


Entire connection is encrypted; looks like
Telnet


SFTP


FTP running through an SSH tunnel


Can get a dedicated server and client for
this

VoIP


Voice over IP


Phone calls over the network


Works with DSL to cable to satellite


Skype is completely proprietary


Low latency (time for packet to get there)
is important


Adapter is built into the cable modem from
Time Warner

Remote Desktop


Programs that allow you to run another
computer


Also called Terminal Emulation or VNC


We will do this, both Remote Desktop and
Ultra
-
VNC later

Virtual Private Network


An encrypted tunnel requires endpoints
with dedicated IP addresses; server at one
end and client at the other


Can be a dedicated box (router)


Point
-
to
-
point Tunneling Protocol (PPTP)


Employee to home office; Routing and
Remote Access Service (RRAS) on server


Remote gets address on LAN

LDAP


Lightweight Directory Access Protocol


Used to do anything with Active Directory

SNMP


Simple Network Management Protocol


Enables remote query and remote
configuration of just about anything on a
network, provided it is SNMP
-
capable

SMB


Server Message Block


Tools that get PC’s names around the
network


NetBIOS names are gone; SMB is the
reason that Network can show you all the
computers on you network


SAMBA emulates SMB

No Connectivity


Rule out the network issue(s) first


Ping the URL; should get an IP address
and successful ping; no IP means DNS
issue


“Repair” connection


Try another DNS server 8.8.8.8 or 8.8.4.4

Limited Connectivity


The dreaded APIPA address: 169.254.x.x


Means no DHCP server is working
(check/restart router)

Local
-
only Connectivity


Could be a router problem (I had to get a
new one)


If no external (WAN) IP address it’s time to
call ISP

Slow Transfer Speed


It’s a bandwidth issue; similar to traffic on
the freeway


Buy more bandwidth?


QoS = Quality of Service; can limit usage
by application, IP address and others; find
it on router’s configuration

Safe Surfing


Need firewall


either Windows, router or
third party


Need antivirus


either pay for it (Norton)
or free download (AVG Free)


Need antispam software (Ad
-
Aware,
Spybot Search and Destroy)


Watch what you click on!!!!