Tips for The Certified #Kubernetes Exams: CKA and CKAD in 2020:
https://dev.to/scriptautomate/tips-for-the-certified-kubernetes-exams-cka-and-ckad-49mn
https://dev.to/scriptautomate/tips-for-the-certified-kubernetes-exams-cka-and-ckad-49mn
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Tips for The Certified Kubernetes Exams: CKA and CKAD in 2020
UPDATED 05/05/2020: Updated a handful of links based on the April 2020 changes to both exams, having...
A full stack of technologies and utilities for becoming professionals in #DevOps
https://xebialabs.com/periodic-table-of-devops-tools/
https://xebialabs.com/periodic-table-of-devops-tools/
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The Open Systems Interconnection (OSI) Model
The Open Systems Interconnection (OSI) model was created to standardize the language used to describe networking protocols. It defines the manner in which systems communicate with one another using abstraction layers. Each layer communicates with the layer directly above and below. Not all layers are used at all times.
The Open Systems Interconnection Model
Layer Name Description
7) - -Application--Most networking stacks have a concept of the application layer.
6) Presentation--Most networking stacks combine the presentation layer in layers 4, 5, or 7.
5) - - Session--Sometimes used by different stacks, often combined into other layers (7 or 6).
4) Transport--Most networking stacks have a concept of the transport layer.
3) - - Network--Most networking stacks have a concept of the network layer.
2) Data - - LinkMost networking stacks have a concept of the data link layer.
1) Physical--Most networking stacks have a concept of the physical layer.
There are other models which are used to talk about networking. The most popular networking stack on the Internet today is the Internet Protocol Suite. The Internet Protocol Suite can be described using a subset of the OSI model.
The Open Systems Interconnection (OSI) model was created to standardize the language used to describe networking protocols. It defines the manner in which systems communicate with one another using abstraction layers. Each layer communicates with the layer directly above and below. Not all layers are used at all times.
The Open Systems Interconnection Model
Layer Name Description
7) - -Application--Most networking stacks have a concept of the application layer.
6) Presentation--Most networking stacks combine the presentation layer in layers 4, 5, or 7.
5) - - Session--Sometimes used by different stacks, often combined into other layers (7 or 6).
4) Transport--Most networking stacks have a concept of the transport layer.
3) - - Network--Most networking stacks have a concept of the network layer.
2) Data - - LinkMost networking stacks have a concept of the data link layer.
1) Physical--Most networking stacks have a concept of the physical layer.
There are other models which are used to talk about networking. The most popular networking stack on the Internet today is the Internet Protocol Suite. The Internet Protocol Suite can be described using a subset of the OSI model.
OSI Layer 7: Application Layer
The Application Layer is the most well-known. This layer is at the top of the stack and deals with the protocols which make a global communications network function.
Some of the common protocols which exist in the Application Layer are:
HTTP: Hypertext Transfer Protocol
SMTP: Simple Mail Transfer Protocol
DNS: Domain Name System
FTP: File Transfer Protocol
DHCP: Dynamic Host Configuration Protocol.
Protocols at this level are the most familiar to users. They are defined by RFC1123. To learn more, take a look at the Requirements for Internet Hosts -- Application and Support memo.
The Application Layer is the most well-known. This layer is at the top of the stack and deals with the protocols which make a global communications network function.
Some of the common protocols which exist in the Application Layer are:
HTTP: Hypertext Transfer Protocol
SMTP: Simple Mail Transfer Protocol
DNS: Domain Name System
FTP: File Transfer Protocol
DHCP: Dynamic Host Configuration Protocol.
Protocols at this level are the most familiar to users. They are defined by RFC1123. To learn more, take a look at the Requirements for Internet Hosts -- Application and Support memo.
OSI Layer 6: Presentation Layer
The Presentation Layer is commonly rolled up into a different layer. This layer deals with the formatting of data, e.g. conversion of Extended Binary Coded Decimal Interchange Code (EBCDIC) to American Standard Code for Information Interchange (ASCII).
For example, the HTTP protocol (an Application Layer protocol) has methods for converting character encoding. In other words, this Presentation Layer step happens at the Application Layer.
Many networking stacks and protocols make no distinction between layers 6 and 7.
The Presentation Layer is commonly rolled up into a different layer. This layer deals with the formatting of data, e.g. conversion of Extended Binary Coded Decimal Interchange Code (EBCDIC) to American Standard Code for Information Interchange (ASCII).
For example, the HTTP protocol (an Application Layer protocol) has methods for converting character encoding. In other words, this Presentation Layer step happens at the Application Layer.
Many networking stacks and protocols make no distinction between layers 6 and 7.
OSI Layer 5: Session Layer
The Session Layer deals with managing of session data. It creates a semi-permanent connection, which is then used for communications.
Many of the RPC-type protocols depend on this layer:
NetBIOS: Network Basic Input Output System
RPC: Remote Procedure Call
PPTP: Point to Point Tunneling Protocol.
This layer is used by protocols which need reliable sessions, such as videoconferencing and SOCKS proxy.
If an established connection is lost or disrupted, this layer may try to recover the connection.
If a connection is not used for a long time, the session layer may close and then reopen it.
The Session Layer deals with managing of session data. It creates a semi-permanent connection, which is then used for communications.
Many of the RPC-type protocols depend on this layer:
NetBIOS: Network Basic Input Output System
RPC: Remote Procedure Call
PPTP: Point to Point Tunneling Protocol.
This layer is used by protocols which need reliable sessions, such as videoconferencing and SOCKS proxy.
If an established connection is lost or disrupted, this layer may try to recover the connection.
If a connection is not used for a long time, the session layer may close and then reopen it.
OSI Layer 4: Transport Layer
The Transport Layer is responsible for the end-to-end communication protocols. Data is properly multiplexed by defining the source and destination port numbers. This layer also deals with reliability by adding check sums, doing request repeats, and avoiding congestion.
Some of the common protocols in the Transport Layer are:
TCP: Transmission Control Protocol
It is the main component of the TCP/IP (Internet Protocol Suite) stack. It is useful when data integrity, ordered delivery, and reliability are important. It is the backbone to many of the most popular protocols.
UDP: User Datagram Protocol
This is another popular component of the Internet Protocol Suite stack. It is useful when transmission speed is important and the integrity of the data isn't as important, or is managed by an above layer.
SCTP: Stream Control Transmission Protocol
It uses port numbers to allow for connection multiplexing.
The Transport Layer is responsible for the end-to-end communication protocols. Data is properly multiplexed by defining the source and destination port numbers. This layer also deals with reliability by adding check sums, doing request repeats, and avoiding congestion.
Some of the common protocols in the Transport Layer are:
TCP: Transmission Control Protocol
It is the main component of the TCP/IP (Internet Protocol Suite) stack. It is useful when data integrity, ordered delivery, and reliability are important. It is the backbone to many of the most popular protocols.
UDP: User Datagram Protocol
This is another popular component of the Internet Protocol Suite stack. It is useful when transmission speed is important and the integrity of the data isn't as important, or is managed by an above layer.
SCTP: Stream Control Transmission Protocol
It uses port numbers to allow for connection multiplexing.
Transport Layer Ports
Transport layer protocols use ports to distinguish between different types of traffic or to do multiplexing. The ports are classed in three different ways.
Transport Layer Ports
Well-Known Ports (0-1023)
They are assigned by the Internet Assigned Numbers Authority (IANA), and usually require super-user privilege to be bound. Some of the well-known ports are: 22 TCP: SSH; 25 TCP: SMTP; 80 TCP: HTTP; 443 TCP: HTTPS.
Registered Ports (1024-49151)
Registered ports are also assigned by the IANA. They can be bound on most systems by non-super-user privilege. Some of the registered ports are: 1194 TCP/UDP: OpenVPN; 1293 TCP/UDP: IPSec; 1433 TCP: MSSQL Server.
Dynamic or Ephemeral Ports (49152-65535)
The Ephemeral ports are used as source ports for the client-side of a Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection. You can also use the Ephemeral ports for a temporary or non-root service.
Transport layer protocols use ports to distinguish between different types of traffic or to do multiplexing. The ports are classed in three different ways.
Transport Layer Ports
Well-Known Ports (0-1023)
They are assigned by the Internet Assigned Numbers Authority (IANA), and usually require super-user privilege to be bound. Some of the well-known ports are: 22 TCP: SSH; 25 TCP: SMTP; 80 TCP: HTTP; 443 TCP: HTTPS.
Registered Ports (1024-49151)
Registered ports are also assigned by the IANA. They can be bound on most systems by non-super-user privilege. Some of the registered ports are: 1194 TCP/UDP: OpenVPN; 1293 TCP/UDP: IPSec; 1433 TCP: MSSQL Server.
Dynamic or Ephemeral Ports (49152-65535)
The Ephemeral ports are used as source ports for the client-side of a Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection. You can also use the Ephemeral ports for a temporary or non-root service.
OSI Layer 3: Network Layer
The Network Layer is all about routing packets. This layer is responsible for getting the packets to the next point in the path to the destination. So, this layer deals with routing and packet forwarding, as well as with managing the quality of service.
In many cases, the final destination is not adjacent to this machine, so the packets are routed based on the local routing table information.
It is connectionless; connection tracking can happen at the layers above. Common protocols are IPv4 and IPv6, and is the backbone of the internet.
Many routing and control protocols live at this layer, such as:
IP: Internet Protocol
OSPF: Open Shortest Path First
IGRP: Interior Gateway Routing Protocol
ICMP: Internet Control Message Protocol.
The Network Layer is all about routing packets. This layer is responsible for getting the packets to the next point in the path to the destination. So, this layer deals with routing and packet forwarding, as well as with managing the quality of service.
In many cases, the final destination is not adjacent to this machine, so the packets are routed based on the local routing table information.
It is connectionless; connection tracking can happen at the layers above. Common protocols are IPv4 and IPv6, and is the backbone of the internet.
Many routing and control protocols live at this layer, such as:
IP: Internet Protocol
OSPF: Open Shortest Path First
IGRP: Interior Gateway Routing Protocol
ICMP: Internet Control Message Protocol.
Originally the datagram service for TCP, the Internet Protocol now transfers many different higher level protocols. The Internet Protocol has two main functions
Addressing
The addressing function examines the address on the incoming packet and decides if the datagram (packet) is for the local system or for another system. If the address indicates the datagram is for the local system, the headers are removed and the datagram is passed up to the next layer in the protocol stack. If the address indicates the datagram is for another machine, then it is passed to the next system in the direction of the final destination.
Fragmentation
The fragmentation component will split and re-assemble the packets if the path to the next system uses a smaller transmission unit size.
Addressing
The addressing function examines the address on the incoming packet and decides if the datagram (packet) is for the local system or for another system. If the address indicates the datagram is for the local system, the headers are removed and the datagram is passed up to the next layer in the protocol stack. If the address indicates the datagram is for another machine, then it is passed to the next system in the direction of the final destination.
Fragmentation
The fragmentation component will split and re-assemble the packets if the path to the next system uses a smaller transmission unit size.
OSI Layer 2: Data Link Layer
The Data Link Layer deals with transferring data between network nodes:
Adjacent nodes in a Wide Area Network (WAN)
Nodes on the same Local Area Network (LAN) segment.
Some of the common Data Link Layer protocols are:
Ethernet
ARP: Address Resolution Protocol
PPP: Point to Point Protocol
STP: Spanning Tree Protocol.
The Data Link Layer deals with transferring data between network nodes:
Adjacent nodes in a Wide Area Network (WAN)
Nodes on the same Local Area Network (LAN) segment.
Some of the common Data Link Layer protocols are:
Ethernet
ARP: Address Resolution Protocol
PPP: Point to Point Protocol
STP: Spanning Tree Protocol.