2.0 Networking

Question 1

A series of moving vans

Answer 1

Efficiently move large amounts of data
        • Use a shipping truck
• The network topology is the road
         • Ethernet, DSL, cable system
• The truck is the Internet Protocol (IP)
          • We’ve designed the roads for this truck
• The boxes hold your data
         • Boxes of TCP and UDP
• Inside the boxes are more things
         • Application information

Question 2

TCP and UDP

Answer 2

Transported inside of IP
-Encapsulated by the IP protocol
Two ways to move data from place to place
-Different features for different applications
OSI Layer 4
-The transport layer
Multiplexing
-Use many different applications at the same time
-TCP and UDP

Question 3

TCP - Transmission Control Protocol

Answer 3

Connection-oriented
-A formal connection setup and close
"Reliable" delivery
-Recovery from errors
-Can manage out-of-order messages or 
  retransmissions
Flow control
-The receiver can manage how much data is sent

Question 4

UDP-User Datagram Protocol

Answer 4

Connectionless
-No formal open or close to the connection
“Unreliable” delivery
-No error recovery
-No reordering of data or retransmissions
No flow control
-Sender determines the amount of data transmitted

Question 5

Speedy delivery

Answer 5

The IP delivery truck delivers from one (IP) address to another (IP) address
-Every house has an address, every computer has an IP address
Boxes arrive at the house/IP address
-Where do the boxes go?
-Each box has a room name
Port is written on the outside of the box
-Drop the box into the right room

Question 6

Lots of ports

Answer 6

IPv4 sockets - Server IP address, protocol, server application port number
-Client IP address, protocol, client port number
Non-epthemeral ports - permanent port numbers
-Ports 0 through 1,023
-Usually on a server or service
Ephemeral ports - temporary port numbers
-port 1,024 through 65,545
-Determined in real-time by the client

Question 7

Port numbers

Answer 7

TCP and UDP ports can be any number between 0 and 65,535
Most servers (services) use non-ephemeral (not-temporary) port numbers
-This isn’t always the case
-It’s just a number
Port numbers are for communication, not security
Service port numbers need to be “well known”
TCP port numbers aren’t the same as UDP port numbers.

Question 8

FTP - File Transfer Protocol

Answer 8

tcp/20 (active mode data), tcp/21 (control)
-Transfers files between systems
Authenticates with a username and password
-some systems use a generic/anonymouse login
Full-featured functionality
-List, add, delete, etc.

Question 9

SSH - Secure Shell

Answer 9

Encrypted communication link - tcp/22

-looks and acts the same as Telnet

Question 10

Telnet

Answer 10

Telnet - Telecommunication Network-tcp/23
Login to devices remotely
Console access
In-the-clear communication
Not the best choice for production systems

Question 11

SMTP - Simple Mail Transfer Protocol

Answer 11

Server to server email transfer -tcp/25
Also used to send mail from a device to a mail server
-commonly configured on mobile devices
and email clients
Other protocols are used for clients to recieve email
-IMAP, POP3

Question 12

DNS - Domain Name System

Answer 12

Converts a names to IP addresses - udp/53
www.professormesser.com= 162.159.246.164
These are very critical resources
-usually multiple DNS servers are in production

Question 13

HTTP and HTTPS

Answer 13

Hypertext Transfer Protocol - tcp/80
-communication in the browser
-and by other applications
In the clear or encryped - HTTPS - tcp/443
-supported by nearly all web servers and clients

Question 14

POP / IMAP

Answer 14

Receive emails from an email server
-authenticate and transfer
POP - Post office Protocol version 3 - tcp/110
-basic mail transfer functionality
IMAP4
-Internet Message Access Protocol v4 - tcp/143
-includes management of email inbox from multiple clients

Question 15

RDP - Remote Desktop Protocol

Answer 15

Share a desktop from a remote location over tcp/3389
• Remote Desktop Services on many Windows versions
• Can connect to an entire desktop
or just an application
• Clients for Windows, macOS, Linux, Unix,
iPhone, Android, and others

Question 16

SMB - Server Message Block

Answer 16

Protocol used by Microsoft Windows
• File sharing, printer sharing
• Also called CIFS (Common Internet File System)
• Using NetBIOS over TCP/IP
• udp/137 - NetBIOS name services (nbname)
• udp/138 - NetBIOS datagram service (nbdatagram)
• tcp/139 - NetBIOS session service (nbsession)
• Direct over tcp/445 (NetBIOS-less)
• Direct SMB communication over TCP
without the NetBIOS transport

Question 17

AFP(Apple Filing Protocol)

Answer 17

File services in macOS
• tcp/548
• Works with SLP (Service Location Protocol)
• tcp/427 and udp/427
• Populates the list of available devices
• File management
• Copy, move, delete files

Question 18

DHCP - Dynamic Host Configuration Protocol

Answer 18

Automated configuration of IP address, subnet mask
and other options
• udp/67, udp/68
• Requires a 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 intervals
• DHCP reservation
• Addresses are assigned by MAC address
in the DHCP server
• Quickly manage addresses from one location

Question 19

LDAP (Lightweight Directory Access Protocol)

Answer 19

tcp/389
• Store and retrieve information in a network directory
• Commonly used in Microsoft Active Directory

Question 20

SNMP - Simple Network Management Protocol

Answer 20

Gather statistics from network devices
• Queries: udp/161
• Traps: udp/162
• v1 – The original
• Structured tables, in-the-clear
• v2 – A good step ahead
• Data type enhancements
• Bulk transfers, still in-the-clear
• v3 – A secure standard
• Message integrity
• Authentication, encryption