COMPUTER NETWORKINGWORKSHOP

Private Cloud and Remote PC ControlInstructor: Forte, Sit King Lok (forte@cuhk.edu.hk)

Version 1.2

AGENDA• Cabling (Quick review)

• Wi-Fi (Quick review)

• Router purchase (Quick review)

• IP

• TCP/IP port

• Application layer service

• Troubleshooting

CABLING

Review

ISP

Local Overseas

PCCWHKBN

3 HK (Hutchison)Wharf T&T

i-Cable

AT&TNTT (docomo)

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ISP• Dial-up

• Use existing telephony network

• DSL

• Use metal cable network

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• FTTx

• FTTB(Fiber To The Building)

• FTTH (Fiber To The Home)

NETWORK DIAGRAM

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MODEM

• Analog ⇔Digital

• Provided by ISP

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CABLE TYPES

• LAN cable

• RJ45 head

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CABLE TYPES• Cat5

• Usually100Mbps Max.

• Cat5e

• Improved Cat5 support 1000Mbps Max.

• Cat6

• Improved Cat5/5e support 1000Mbps Max. and reduce noise

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WI-FI

Review

IEEE 802.11

• Protocol(standard) adopted by Wi-Fi

• IEEE802.11a/b/g/n/ac

• Both the router and your devices should support the same protocol

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IEEE 802.11

802.11a 802.11b 802.11g 802.11n 802.11ac

Speed 54Mbps 11/22Mbps 54Mbps 65-600Mbps 290-6900Mbps

Frequency 3.7/5GHz 2.4GHz 2.4GHz 2.4/5GHz 5GHz

Bandwidth 20MHz 22MHz 20MHz 20/40MHz 20/40/80/160MHz

Release date Sep 1999 Sep 1999 Jun 2003 Oct 2009 Dec 2013

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IEEE 802.11

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WEP, WPA, WPA2• Security protocol to encrypt/decrypt wireless data

• WEP

• Can be easily hacked in few minutes

• WPA

• Better security than WEP but still can be hacked 14

WEP, WPA, WPA2• WPA2

• Currently best security protocol

• Hard to be hacked provided that a “secure” password is used

• Mode / Version

• WPA2 Personal

• WPA2 Enterprise

• Encryption

• TKIP

• CCMP (AES, AES-CCMP)

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PASSWORD• Set a secured password

• Long enough (>8 characters)

• Combination of numbers, characters (upper & lower case) and punctuations

• No birthday, phone number, HKID, or any other personal information

• No dictionary words

• Good password examples

• t9^Xo03#”!yzTyUf48>

• G00dP@ssw0rd

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SSID

• The identifier(name) of the Wi-Fi network

• Can be hidden from end users, but not hackers

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ROUTER PURCHASE

Review

ROUTER PURCHASE• Know the price range by your usage

• Only need to have a stable, fast-enough, secured Internet connection →$200~400

• Need to have very fast LAN communication (e.g. transferring large files among your PCs) →$400~700

• Require advanced features / high performance(e.g. sharing drive thru USB3.0 / QoS / high wall penetrating power) →$700~

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ROUTER PURCHASE• Metrics

• Support 802.11ac?

• Support Dual Band (802.11n+ac)?

• What is the wireless speed?

• How many LAN ports?

• Does it have USB2.0/3.0?

• Can it fully cover your home? (no. of antenna / penetrating power)

• Does the firmware provide the feature you need?

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ROUTER PURCHASE

• A web site which has many information about router purchase

• http://upsangel.com

• TP-LINK emulators

• http://www.tp-link.com/en/emulators.html 21

IP

IP• IP (Internet Protocol) address

• Address standard for computing devices over network

• Version

• IPv4

• IPv6

• One IP per network interface 23

FORMAT• Four octets separated by dots

• From 0.0.0.0 to 255.255.255.255

• Examples

• 192.168.1.1

• 27.126.208.30 24

SUBNET MASK• An IP address helping to represent a range of continuous IP addresses (subnet)

• Can be abbreviated to “/x”, where x is a number from 0 to 32

• Example of a subnet mask

• 255.255.255.0

• Examples of a subnet representation

• 192.168.1.0/255.255.255.0

• 192.168.1.0/24

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SUBNET MASKCIDR Subnet Mask Total IPs/32 255.255.255.255 1/31 255.255.255.254 2/30 255.255.255.252 4/29 255.255.255.248 8/28 255.255.255.240 16/27 255.255.255.224 32/26 255.255.255.192 64/25 255.255.255.128 128/24 255.255.255.0 256/23 255.255.254.0 512/22 255.255.252.0 1024/21 255.255.248.0 2048/20 255.255.240.0 4096/19 255.255.224.0 8192/18 255.255.192.0 16,384/17 255.255.128.0 32,768/16 255.255.0.0 65,536/15 255.254.0.0 131,072/14 255.252.0.0 262,144/13 255.248.0.0 524,288/12 255.240.0.0 1,048,576/11 255.224.0.0 2,097,152/10 255.192.0.0 4,194,304/9 255.128.0.0 8,388,608/8 255.0.0.0 16,777,216

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PRIVATE IP• Reserved IP ranges used within LAN (Local Area Network)

Class Range Subnet Mask Total IPs

Class A 10.0.0.0 - 10.255.255.255 255.0.0.0 16,777,216

(16,777,216 × 1 subnet)

Class B 172.16.0.0 - 172.31.255.255 255.240.0.0 1,048,576

(65,536 × 16 subnet)

Class C 192.168.0.0 - 192.168.255.255 255.255.0.0 65,536

(256 × 256 subnet)

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NAT• Translate IP address

• Use one IP address to represent a subnet

• Common use of NAT

• Get one WAN IP from ISP

• Create many LAN IPs by the router 28

DHCP

• Automatically “create” and assign IPs to each of your devices

• DHCP pool

• A private IP subnet reserved for DHCP

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STATIC AND DYNAMIC IP• Static IP

• Does not change from time to time

• Dynamic IP

• IPs assigned by DHCP

• Reassignment occurs from time to time

• Most ISP gives you a dynamic IP 30

MAC ADDRESS• Yet another address system

• One MAC address per network interface

• Unique throughout the world

• Six octets in hexadecimal separated by colons or hyphens

• From 00:00:00:00:00:00 to FF:FF:FF:FF:FF:FF

• Examples

• 04-A3-43-5F-43-23

• 32:61:3C:4E:B6:05

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TCP/IP PORT

TCP/IP PORT• Identifier which recognizes to the level of services

(processes)

• On both ends of a communication

• Two types

• TCP

• UDP 33

FORMAT• From 0 to 65535

• Specified after an IP, separated by a colon

• Examples

• 192.168.1.1:22

• 27.126.208.30:80 34

PORT FORWARDING

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PORT FORWARDING

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PORT FORWARDING

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APPLICATION LAYER SERVICE

APPLICATION LAYER SERVICE• Process

• The “working man” of an application

• One application can have many processes

• Service

• Process that serve other computers

• In general, we call the computer running services a “server” 39

FTP

• FTP (File Transfer Protocol)

• Used for file sharing

• Allow you to create a PRIVATE CLOUD DRIVE

• Common port: 20/TCP, 21/TCP

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VNC

• VNC (Virtual Network Computing)

• Used for remotely controlling a computer

• Allow you to use your PC from anywhere as if you are in front of it

• Common port: 5900/TCP, UDP 41

RDC

• RDC (Remote Desktop Connection)

• Simular to VNC

• Microsoft-proprietary software

• Common port: 3389/TCP, UDP

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WEB• HTTP

• Used for hosting web sites (No encryption)

• Common port: 80/TCP, UDP

• HTTPS

• Same as HTTP but with encryption (i.e. secured)

• Common port: 443/TCP, UDP 43

Optional

VPN

• VPN (Virtual Private Network)

• Used for connecting to your LAN from anywhere

• Common VPN solution

• PPTP, L2TP, OpenVPN 44

Optional

TROUBLESHOOT

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FIREWALL ISSUE

• Firewall (sometimes bundled with anti-virus softwares) may block incoming traffics

• Solution

• Set the firewall to allow traffics of specific destination port to pass through

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ISP ISSUE

• Some ISP may block traffics destined to a specific port (e.g. Blocking all traffics to port 80 disallows you from setting up web server)

• Workaround

• Use other “non-common” port numbers (e.g. Use 81 instead of 80 for web server)

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DDNS

• DNS (Domain Name System) translate IPs to meaningful domain names (e.g. www.cuhk.edu.hk)

• ISP usually provides dynamic IPs for home users

• DDNS (Dynamic Domain Name System) updates the mapping of IP to domain name once the IP changed

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Optional

USEFUL COMMAND• ifconfig

• ping

• traceroute

• nslookup

• nmap

• netstat 49

Optional

REFERENCE• Explanation of subnet mask in details

• https://www.iplocation.net/subnet-mask

• Port forwarding tutorial video

• https://www.youtube.com/watch?v=FFR8Tz0Q6T8

• File sharing tutorial video

• https://www.youtube.com/watch?v=uFQhawnWOrI

• A company providing free DDNS service

• http://www.noip.com

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