computer networking workshop · 2018. 10. 19. · ieee 802.11 802.11a 802.11b 802.11g 802.11n...
TRANSCRIPT
COMPUTER NETWORKINGWORKSHOP
Private Cloud and Remote PC ControlInstructor: Forte, Sit King Lok ([email protected])
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)
4
ISP• Dial-up
• Use existing telephony network
• DSL
• Use metal cable network
5
• FTTx
• FTTB(Fiber To The Building)
• FTTH (Fiber To The Home)
NETWORK DIAGRAM
6
MODEM
• Analog ⇔Digital
• Provided by ISP
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CABLE TYPES
• LAN cable
• RJ45 head
8
CABLE TYPES• Cat5
• Usually100Mbps Max.
• Cat5e
• Improved Cat5 support 1000Mbps Max.
• Cat6
• Improved Cat5/5e support 1000Mbps Max. and reduce noise
9
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
35
PORT FORWARDING
36
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
42
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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