Network topology is the road: Ethernet DSL cable system
The truck is the internet protocol: we have designed the roads for this truck
Inside this truck we have the boxes that hold your data: boxes of TCP and UDP
Inside the boxes are more things – Application information
Port Number: TCP and UDP ports can be any number between 0 and 65,535
Ports are categorize as non-ephemeral (not-temporary) (0-1023) majorly used by servers and ephemeral
(1024 - 65535) majorly used by clients. But this may not always the case----it’s just a number
TCP port number aren’t the same as UDP port numbers
ICMP – Internet Control Message Protocol – for some administrative tasks – to check if host is live
Common Ports:
Telnet – Telecommunication Network: tcp/23 – login to device remotely and give console access, uses
clear communication and so not the best choice for production systems
SSH – Secure Shell : alternative to telnet – most administrator uses SSH:
Encrypted communication link – tcp/22 port
Looks and act the same as telnet
DNS – Domain Name System: Converts names to IP address (happens behind the seen) – udp/53
SMTP – Simple Mail Transfer Protocol – tcp/25: server to server mail transfer (One mail server to
another), also used to send mail from device to a mail server (for out-going mail)
Other protocols are used for clients to receive email – IMAP, POP3 (used for all of incoming mail
communication)
SFTP – Secure FTP: Uses the SSH File Transfer Protocol – tcp/22: Encrypted communication using SSH
FTP – File Transfer Protocol – tcp/20 (active mode data), tcp/21 (control)
Transfer files between systems, Authenticate with user name & password
Full-featured functionality (list, add, delete, etc.)
TFTP – Trivial File Transfer Protocol (Simple form of FTP) – udp/69
Very simple file transfer application: read files and write files
No authentication: Not used in production system
DHCP – Dynamic Host Configuration Protocol: udp/67, udp/68
Automate configuration of IP address, subnet mask, DNS setting & other options
Required DHCP server: Server, appliance, integrated into a SOHO router, etc.
Dynamic/pooled: IP addresses are assigned in real-time from a pool
Each system is given a lease and must renew at set interval
DHCP reservation: addresses are assigned by MAC address in the DHCP server
Quickly manage addresses from one location
HTTP and HTTPS: communication in the browser and by other applications
HTTP – tcp/80
HTTPS – tcp/443: web server communication with encryption
SNMP (Simple Network Management Protocol)- udp/161: for managing routers, switches, servers and
other infrastructure devices by gathering matrices (statics) from network devices.
V1: The original – structured table and in-the-clear (not encrypted)
V2: Data type enhancements, bulk transfer, still in-the-clear
V3: A secure standard – message integrity, authentication, encryption
RDP (Remote Desktop Protocol) – tcp/3389: Share a desktop from a remote location
Remote Desktop Service on many Windows version
Can connect to an entire desktop or just an application
RD Clients also available for other OS like – Windows, MacOS, LiNUX, iPhone etc.
NTP (Network Time Protocol) – udp/123: Switches, routers, firewall, servers, workstations
Every device has its own clock
Synchronizing the clock becomes critical: log files, authentication information, outage details
Automatic updates: No flashing 12:00 lights
Flexible – you control how clocks are updated
Very accurate: accuracy is better than 1 milliseconds on a local network
SIP (Session Initiation Protocol) – tcp/5060, tcp5061: Voice over IP (VoIP) signaling
Setup and manage VoIP sessions: Call, ring, hang up
Extended voice communication ; Video conferencing, instant messaging, file transfer etc.
SMB (Server Message Block): Protocol used by Miscrosoft Windows
File sharing, printer sharing
Also called common internet file system (CIFS)
Direct over tcp/445 (NetBIOS-less): Direct SMB communication over TCP without the NetBIOS
transport
POP/IMAP: Receive emails from an email server
Authenticate and transfer
POP3 (Post Office Protocol version 3) – tcp/110: basic mail transfer functionality
IMAP4 (Internet Message Access Protocol v4 – mostly used) – tcp/143
Includes management of email inboxes from multiple clients
LDAP/LDAPS:
LDAP (Lightweight Directory Access Protocol ) – tcp/389
Store and retrieve information in a network directory
LDAPS(LDAP Secure) – tcp/636
A non-standard implementation of LDAP over SSL
H.323 – tcp/1720: SIP is not the only VoIP control protocol, we may also use H.323:
Voice over IP (VoIP) signaling
ITU telecommunication H.32x protocol series
Setup (Phone calls) and manage VoIP sessions: call ring, hang up
This is one of the earliest VoIP protocol and still in use today
………………………………………………………………………………………….
OSI Model (Open System Interconnection Reference Model): 7 layers
………………………..
Introduction to Ethernet:
CSMA/CD (Collision Detection) – used in case of Half-duplex communication in wired network using Hub
– Now not in use, as mostly in layer 2, now switches are being used that configured to communicate in
full-duplex mode
CSMA/CA (Collision Avoidance) – Used in wireless network, as collision detection is not possible in case
of wireless. So it uses RTS (Request to send) and CTS (Clear To Send) messages with access points before
sending the data. This also removes the hidden node issue of wireless communication.
…………..
Network Switching:
The Switch: Forward or Drop frames – based on the destination MAC address