Chapter 1 - Ports, Protocols and OSI Flashcards
TCP Stands for?
Transmission Control Protocol
What’s does TCP do?
Established and maintains network communication to exchange data till complete.
What other protocol works along side TCP?
Internet Protocol (IP)
What type of connection is it? And what does it mean?
Connection orientated.
Provides guaranteed packet delivery and packet re transmission but use of acknowledgments.
Pro and Con of TCP?
Is slow
More reliable
What protocol uses TCP?
File transfer Protocol (FTP)
Port 20 = Data port connecting back to client client (Passive)
Port 21 = Command Port initiates by client (Active)
What does IP stand for?
Internet Protocol
What is IP Protocol used for?
Deliver data from one computer to another over the internet
What does IP it specify? And what other Protocol is used?
Specifies the
- the format of packets
- Addressing Scheme
Also uses the TCP Protocol (TCP/IP)
What is a connection less Protocol?
Packets have no relation to the other units of data.
UDP
Do packets using IP assemble in correct order?
Yes. TCP assembles packets in the correct order even if packets arrive out of order.
Can IP send packets along different routes to the same machine?
Yes and TCP will assemble them in correct order.
What layer of the OSI Model does IP OPERATE?
Network Layer
What does IP Handel?
Handles routing to ensure packets arrive as the correct location.
IPv4
32bits
4 Bytes
Supports 4 billion addresses
Consists of four groups of 8 bits.
Eg
- 1
- 00010000.11111110.00000001
IPv6
128bit address space
340 Trillion addresses
Format can be compressed by compressing the leading 0 and groups of 0
2001: 0db8:3902:00c2:0000:0000:0000:fe04
2001: db8:3902:c2::fe04
Most recent OSs IPv6 is default but 4 can also be used
Better at handling VOIP and Video conferencing
Is a more complex addressing scheme
What’s is UDP?
User Datagram Protocol
Ideal for speed
Not as reliable as TCP
Faster than TCP
Data that suffers data loss doesn’t effect the overall quality and relays on app to resend lost packets.
Operates and transport layer
UDP Transmission Services
Trivial File Transfer Protocol (TFTP) Real Time Streaking Protocol (RTSP) Simple Network Protocol (SNP) Domain Names System (DNS) Internet Control Message Protocol (ICMP)
What does ICMP do?
Provides error reporting and message generating when problems in delivering IP packets
Is a UDP Protocol
What can send ICMP messages?
Any IP Network device and send, receive and processes messaged.
-Router - Host - Service
One of the main internet protocols
Commonly used in diagnostics and troubleshooting with PING and TRACERT commands to get a status reply.
ICMP message types
Error Reporting when something goes wrong
Query Messages when you want to ask about the status of a device.
Doesn’t correct issues.
L
Connection orientated Protocol benefit and Con
Benefits
Less prone to error
More reliable
Data arrives in correct sequence
State fuel connections
Con
Slower protocol
What is a connectionless Protocol?
When communication is sent between two network endpoints without prior arrangement.
Device sends messages prior to ensuring receiving device is ready.
Some protocols can allow for error correction is needed
What are some connectionless protocols?
UDP
IP
ICMP
IPX
Connectionless Protocol Pro and Conns
Pro
Is a fast protocol
Cons
Not reliable
No error messages of data is dropped
A stakes communication connection.
What is a connection orientated Protocol?
A reliable service that guarantees data will arrive in proper sequence
TCP
Connection less Protocol Broadcast Types
Broadcast
A single message is sent to all hosts on a network simultaneously (1 to many)
Multicast
Message sent to multiple Hosts which belong to a specific multicast group
FTP?
File Transfer Protocol
Port 20 Passive data port where serve connects back to client
Port 22 Active command port used by client to initiate connection
FTP is and client/server config and used to transfer files.
SFTP ensures authentication between user and server
TCP based Protocol
SSH?
Secure Shell
Port 22
Used in Linux/Unix to provide confidentiality and integrity when using an in secure network.
Uses Public Key Cryptography
Commonly used to secure remote network logins.
Telnet?
Port 23
Supports remote logging and communication between two computers
No encryption, data sent in plain text and subject to interception.
Used to run commands or diagnostics on remote systems.
SMTP
Simple Mail Network Protocol
Port 25
Used for sending internet email transmissions to transfer massages from one server to another. (Email)
Send only protocol for email.
SMPT with authentication uses port 587
DNS?
Domain Name System
Port 53
Translates URLs into IP Addresses
Uses both TCP and UDP
DNS servers use hierarchical database containing know IP Addresses and corresponding Domain names.
TCP over port 53
Used for data replication for data being copied to a second server of request 1 fails.
UDP over port 53
Used for simple lookups
WHOIS query
Is a passive DNS assessment without connecting with the target.
DHCP
Dynamic Host Configuration Protocol
Port 67 for servers using UDP
Port 68 for clients using UDP
Used to assign IP addresses to a network device.
IPs can be manually or dynamically assigned.
DHCP requests IP from a sever using DORA DISCOVER OFFER REQUEST ACKNOWLEDGE
DCHP Reservation list
Is a list of IP Addresses which won’t be leased to other devices on the network.
Trivial File Transfer Protocol
Port 69
A network file transfer protocol which uses UDP
HTTPS and HTTPS
HTTPS Port 80/8080
HTTPS Port 443
Sends and receives web based client requests to view HTML pages or data from a browser.
Client uses a URL to locate and request information from a web server.
Requests are sent back using TCP be default over port 80.
Can used UDP.
HTTP is unencrypted
HTTPS secures wen browsing using SSL to provide strong encryption.
PoP3
Post Office Protocol v3
Port 110
Port 995 using SSL
Receive only protocol
As client connects the email is downloaded to the device and deleted from the server once send/receive pressed.
IMAP
Internet Message Access Protocol
Port 143
Port 993 using SSL
Allows emails to sync between multiple devices.
Emails stored on a server instead of being downloaded to a device.
Receive only protocol
NTP
Network Time Protocol
Port 123
Used to sync time between devices.
SNMP
Simple Network Management Protocol
Port 161/162
Is an application protocol.
Manages and monitors network devices to catch problems.
Provides common language for network devices in a LAN or WAN.
SNMP v3
Protects packets in transit by authenticating and encrypting SNMP messages.
LDAP
Leighton Weight Director Access Protocol
Port 389
Port 636 using SSL
Application layer protocol used to search a directory for objects such as
- Organisations - Individuals - Resources - Files and Devices.
Directory allows object organisation BIA a logical hirachy.
Benefits of LDAP?
Allows multiple independent directories Uses a global naming system Runs over TCP/UDP and SSL Supports DMS for name resolution An open source protocol.
SMB?
Server Message Block
Port 446
Used to share access to network resources like
-Files -Printers -Serial Port and Devices
Commonly used when using Network Attached Storage (NAS)
Can connect SMB via AFP for Mac when you specify Port # and URL.
RDP?
Remote Desktop Protocol
Port 3389
Allows remote users to have a GUI while accessing another computer.
Microsoft proprietary protocol
SIP?
Session Initiation Protocol
Port 5060/5061
is a signalling Protocol used for intimating, maintaining and terminating real time sessions like
Voice and Video applications.
OSI Model?
Open System Interconnect
Is an architectural approach to developing network communications
Facilitates consistency when developing apps, protocols and devices.
Layers of the OSI Model?
Has 7 layers
Application Presentation Session Transport Network Data Link Physical
Interaction between top and or bottom layer only
When sending packets begin at the application layer and works down the stack. And back up the layer stack and the receiving end.
Layer 1 OSI
Physical
Transmits digital data bits from sender to receiving device over physical network communication media.
Contains physical devices like hardware and contains the definition of hardware specifications for
-Cables -Connections -NIC -Repeaters -Hubs
Little programming involved.
Functions of ISO Physical layer
Encoding and Signalling
Transforms data from bits into electrical signals which’s are sent over the network.
Data Transmission
Transmitting and receiving of data across the network type (Wired or wireless)
Topology and Physical Network Design
Bit Rate Control
Controls transmission but rage so you don’t over whelm the physical media.
Layer 2 ISO Model
Data Link Layer
Responsible for node to node data delivery which receives data coming down from the network layer and passes down to the physical layer.
It creates frames and adds physical addresses
- FRAMES identify the beginning and end of the transmission*
- Physical Address (MAC) defines who the sender and receiver is*
Features of Data Link layer 2
Error Free Transfer
Other layers can assume error dress transmission over the media
if an error occurs it ensures data re transmission
Defines data format and errors using
-Checksum
A mathematical calculation applies to data which informs you of its value and what the value should be. If value is lost it requests a data resend.
- Source and Destination Addressing.
- Data
Data Link layer functions
- Physical Addressing (MAC)
To detect and recover errors at the Physical layer it uses
1/ Frame Traffic Control
2/ Frame Sequencing
3/ Frame Acknowledgement
4/ Fram Delaminating - identify Start and end
5/ Frame error checking - Check Sum
6/ Establish and Terminate links
7/Media Access Management - which indicates who is using the media at a given time.
8/ Flow Control
9/ Error Control
10/Access Control
Data Link Sub Layer LLC
1/ Logical Link Control (LLC)
The interface between the MedianAccess Methods (Physical Layer) and Network Layer Protocols (Network Layer)
LLC determine if communication within be
1/ Connectionless using UDP OR
2/ Connection Orientated using TCP
- TCP/UDP operate in the transport layer*
- LLC implements the communication protocol type*
Data Link sub layer MAC
Media Access Control
Responsible for connection to the physical media using a MAC address
MAC Address is a
12 digit a hexadecimal number which is unique to each computer/network device.
Layer 3 OSI Model
Networking
Which is responsible for
1/ Patch Addressing
2/ Converts Address from logical which is editable (IP) to physical which is not editable (MAC)
3/ Source to destination delivery which uses routing to get packets delivered from network to network over the internet.
- Routing only required for sending data out of your network. *
- No need for routing on the local network as the MAC address can be used to identify local network devices*
- layer is responsible for defining Networks*
- Defines boundaries of a given network and how to pass data between them*
Network Layer Functions
1/ Subnet Control
Which is a network segment boarded by a router.
It can use throttling to control data transfer.
2/ Subnet usage accounting
Keeps track of frames which can be used to report on how much bandwidth an action takes.
3/ Address Mapping
Translated Logical Address into the physical address.
4/ Inter Networking
Provides logical connection between different Networks and combines various networks to form a larger network.
is the connection of multiple networks located at different locations
5/ Logical Addressing
Enables combining of larger networks and defines a network addressing scheme to uniquely identify each device.
6/ Packetising
Creates packets upon receiving data from upper layers using encapsulation.
IP defines packet format
7/ Fragmentation
Divides larger packets into smaller fragments which can be easily sent on physical medium.
What are subnets used for?
Used by large networks to organise networks into smaller units.
Layer 4 ISO Model
Transport Layer
Manages end to end messages delivering from the source to destination.
- provides error checking to ensure no Duplications or Errors during transfer*
- Message arrives intact and in correct order*
- Provides garunteeded delivery and uses acknowledgements*
Can be TCP or UDP
Transport layer functions
1/Message segmentation
Messages from the session layer are passed into the network layer and splits messages in packets.
2/Message Acknowledgement and Traffic Control
3/ Session Multiplexing
Connects multiple sessions into one logical link and track which messages belong to which session.
4/ Service Point Addressing
Ensures correct packets arrive at correct system and being accessed by correct application.
5/ Flow Control
Prevents source device sending data packets at a faster rate than destination can Handel.
6/ Error Control
Ensures messages arrive without error.
What is the layer 5 OSI Model
Session Responsible for communication between two devices looking after the - Beginning - Maintenance of connection - Ending of a given communication
Regulating flow of data between two devices
Provides a set of guide line over the entire communication
What is session protocol
Defines parameters for connections and manages transfer of data for
- who can transfer and for how long.
Don’t want to leave connection open once transfer complete
Session layer functions
1/ Session Establishment, Maintenance and Transmission
- Establishes two machines to establish a session.
2/ Session Support
- looks after security, Names recognition of users and machines and login credentials.
- Not concerned about sending data but focuses on how we control the passing of data to a machine*
3/ Dialog Control
- Determines which device communicates first and how much data is sent.
- Simplex = one way communication at a time.
- Half Duplex = two way communication but one at a time.
- Full Duplex = Bidorectional communication both at the same time.
4/ Dialog Separation
- Adds check points/markers with a message
- used to indicate beginning and end of a message
- looks after how a message will resume from interruption (maintenance)
Session Layer Protocols
NetBIOS
Names Pipes
RPC
What is the layer 6 OSI Model?
Presentation (Teanslation) layer
Presents data in a uniform format to the application layer and masks differences between different systems.
Translates data into a common format to the application layer at the receiving device.
Presentation lauer Functions
1/ Character Code Translation
ASCII
EBCDIC
Code standards Look after translation Mathias from Binary to character information
2/Data Conversion
- Bit order
- Carriage returns (type writer) / Line feed (Linux)
- Integer floating point to recognise between floating and while integers.
3/ Data Compression
To reduce # of bits transmitted on the network
4/ Data Encryption
Encrypts data for security but also increases file size.
What is the layer 7 OSI Model?
Application layer
Serves as a window for users and application processes accessing a network service.
Interface between the program and protocol Stack
Network services pro side by application layer
- FTP
- DHCP
- DNS
- SMTP
- HTTP
- POP3
- NFS
Application layer functionality
Allows a used to interact with applications.
- It accepts user input and passes data down to the lower layers*
- Allows for easier application compatibility and Implementation and apps don’t have to be re written for different types of network environments*
Examples of application layer functionality
1/Email Services
Email apps don’t need to be consistent to send messages across different networks.
2/ File Transfer, Access and Management (FTAM)
Multiple types of FTAM applications can be used to access and modify files remotely.
3/ Browsers
To provide internet access for all networking environments
- as long as HTTP protocol can be accessed *
- Don’t need to concern with lower layer protocols as an application developer uses the standard protocols for the app to work at the application layer*
