Cybersecurity Operations
The term internet means:
"Network of Networks!"
Any frame less than 64 bytes in length is considered a
"collision fragment" or "runt frame"
Ethernet supports the following data bandwidths:
- 10 Mbps - 100 Mbps - 1000 Mbps (1 Gbps) - 10,000 Mbps (10 Gbps) - 40,000 Mbps (40 Gbps) - 100,000 Mbps (100 Gbps)
To accomplish end-to-end communications across network boundaries, What four basic operations do network layer protocols perform?:
- Address end devices - Encapsulation - Routing - De-encapsulation
TCP/IP Layers
- Application - Transport - Internet - Network Access
What are the 4 Important Rules of network communication
- Encapsulation - Message Formatting - Message size - Message Timing
Message Timing includes important roles of:?
- Flow Control - Response Timeout - Access method
Two benefits of segmenting messages
- Increases speed - Increases efficiency
Two primary benefits of Segmenting messages:
- Increases speed - Increases efficiency
What is the TCP/IP has two important aspects for vendors and manufacturers:
- Open Standard Protocol Suite - Standards-based Protocol Suite
Two layered models used to describe network operations:
- Open System Interconnection (OSI) Reference Model - TCP/IP Reference Model
What are the three addresses of Network Protocols?:
- Protocol Address - Network Host Address - Physical Address
Network protocols:
- Provide the means for computers to communicate on networks - Dictate the message encoding, formatting, encapsulation, size, timing, and delivery options - Define a common format and set of rules for exchanging messages between devices
A message can be delivered in what three different ways:?
- Unicast - Multicast - Broadcast
Three Methods of Message Delivery Options
- Unicast - Multicast - Broadcast
Hexadecimal digits uses numbers
0 to 9 and the letters A to F
4 Layers of a TCP/IP Model
1. Network Access 2. Internet 3. Transport 4. Application
The Maximum frame size for Ethernet is how many bytes?
1518 bytes
The minimum Ethernet frame size is how many bytes?
64 bytes
An Ethernet MAC address is a?:
8-bit binary value expressed as 12 hexadecimal digits (4 bits per hexadecimal digit)
Unicast
A one-to-one delivery option
Standards-Based Protocol
A protocol that has been endorsed by the networking industry and approved by a standards organization
HTTPS (Hypertext Transfer Protocol Secure)
A secure form of HTTP that encrypts the data that is exchanged over the World Wide Web
HTTP (Hyper Text Protocol)
A set of rules for exchanging text, graphic images, sound, video, and other multimedia files on the World Wide Web
TFTP (Trivial File Transfer Protocol)
A simple, connectionless file transfer protocol with best-effort, unacknowledged file delivery. It uses less overhead than FTP
REST (Representational State Transfer)
A web service that uses application programming interfaces (APIs) and HTTP requests to create web applications
A host is transmitting a broadcast. Which host or hosts will receive it?
All hosts in the same network
Tier 1 and Tier 2 ISPs connect through what exchange point?
An Internet Exchange Point (IXP)
Which OSI model layer contains protocols for process-to-process communication?
Application
Which statement describes a characteristic of cloud computing?
Applications can be accessed over the Internet by individual users or businesses using any device, anywhere in the world
How does BYOD change the way in which businesses implement networks?
BYOD Provides flexibility in where and how users can access network resources
Hexadecimal is commonly used to represent?:
Binary Data
Operating without regard to the data carried in each packet allow the network layer to
Carry packets for multiple types of communications between multiple hosts
Dropped frames are likely to be the result of?:
Collisions or other unwanted signals
Network Access
Controls the hardware devices and media that make up the network
Which protocol stack layer encapsulates data into frames?
Data Link
Which Ethernet frame field assists a host in determining if the frame that is received is addressed to it?
Destination Address
Internet
Determines the best path through the network
DHCPv4
Dynamic Host Configuration Protocol for IPv4. A DHCPv4 server dynamically assigns IPv4 addressing information to DHCPv4 clients at start-up and allows the addresses to be re-used when no longer needed
DHCPv6
Dynamic Host Configuration Protocol for IPv6. DHCPv6 is similar to DHCPv4. A DHCPv6 server dynamically assigns IPv6 addressing information to DHCPv6 clients at start-up
IMAP (Internet Message Access Protocol)
Enables clients to access email stored on a mail server as well as maintaining email on the server
POP3 (Post Office Protocol version 3)
Enables clients to retrieve email from a mail server and download the email to the client's local mail application
SMTP (Simple Mail Transfer Protocol)
Enables clients to send email to a mail server and enables servers to send email to other servers
What is the name of the process of adding protocol information to data as it moves down the protocol stack?
Encapsulation
What process involves placing one PDU inside of another PDU?
Encapsulation
Two most commonly deployed LAN technologies
Ethernet and wireless LANs (WLANs)
A web client is receiving a response for a web page from a web server. From the perspective of the client, what is the correct order of the protocol stack that is used to decode the received transmission?
Ethernet, IP, TCP, HTTP
What method can be used by two computers to ensure that packets are not dropped because too much data is being sent too quickly?
Flow Control
Which part of the Ethernet frame helps a destination detect if there are errors in a frame?
Frame Check Sequence
Ethernet is a family of networking technologies defined in the:
IEEE 802.2 and 802.3 standards
Which IP versions are the principle network layer communication protocols?
IP version 4 (IPv4) and IP version 6 (IPv6)
What is the most recent version of IP?
IPv6
What is an example of hexadecimal addressing?
IPv6 addresses
Response Timeout
If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly. The person may repeat the question or instead, may go on with the conversation. Hosts on the network use network protocols that specify how long to wait for responses and what action to take if a response timeout occurs
Dropped frames are considered?:
Invalid
Addressing
Is used by the client to send requests and other data to a server
Ethernet standards define both:
Layer 2 protocols and the Layer 1 technologies
Multicast
One-to-many delivery option
Which Ethernet frame field notifies destinations to get ready for a new frame?
Preamble
Open Standard Protocol
Protocol that is freely available to the public and can be used by any vendor on their hardware or software
Broadcast
Represents a one-to-all message delivery option
4- Application
Represents data to the user, plus encoding and dialog control
Web Server
Runs web server software that allows many computers to access web pages
What is the PDU associated with the transport layer?
Segment
What is the process of dividing a large data stream into smaller pieces prior to transmission?
Segmentation
Which statement accurately describes a TCP/IP encapsulation process when a PC is sending data to the network?
Segments are sent from the transport layer to the internet layer
FTP (File Transfer Protocol)
Sets the rules that enable a user on one host to access and transfer files to and from another host over a network. It is a reliable, connection-oriented, and acknowledged file delivery protocol
Unlike the transport layer (OSI Layer 4), network layer communication protocols (i.e., IPv4 and IPv6)
Specifies the packet structure and processing used to carry the data from one host to another host
SLAAC
Stateless Address Autoconfiguration. A method that allows a device to obtain its IPv6 addressing information without using a DHCPv6 server
File Server
Stores corporate and user files in a central location
3- Transport
Supports communication between various devices across diverse networks
Frame Check Sequence Field
The Frame Check Sequence (FCS) field (4 bytes) is used to detect errors in a frame. It uses a cyclic redundancy check (CRC). The sending device includes the results of a CRC in the FCS field of the frame. The receiving device receives the frame and generates a CRC to look for errors. If the calculations match, no error occurred. Calculations that do not match are an indication that the data has changed; therefore, the frame is dropped. A change in the data could be the result of a disruption of the electrical signals that represent the bits
Preamble and Start Frame Delimiter Fields
The Preamble (7 bytes) and Start Frame Delimiter (SFD), also called the Start of Frame (1 byte), fields are used for synchronization between the sending and receiving devices. These first eight bytes of the frame are used to get the attention of the receiving nodes. Essentially, the first few bytes tell the receivers to get ready to receive a new frame
Which statement is true about the TCP/IP and OSI models?
The TCP/IP transport layer and OSI Layer 4 provide similar services and functions
Ethernet operates in
The data link layer and the physical layer
Protocol Data Unit (PDU)
The form that a piece of data takes at any layer
Which layers provide services to allow end devices to exchange data across networks?
The network layer or OSI Layer 3
Encoding
The process of converting the data message into another format suitable for transmission across the physical medium
Segmentation
The process of dividing a stream of data into smaller units for transmissions over the network
Flow Control
The process of managing the rate of data transmission. It defines how much information can be sent and the speed at which it can be delivered. For example, if one person speaks too quickly, it may be difficult for the receiver to hear and understand the message. In network communication, there are network protocols used by the source and destination devices to negotiate and manage the flow of information
Encapsulation
The process of placing one message format (the letter) inside another message format (the envelope)
De-encapsulation
The process used by a receiving device to remove one or more of the protocol headers
What happens if the size of a transmitted frame is less than the minimum, or greater than the maximum?
The receiving device drops the frame
What layer does IP encapsulate?
The transport layer segment or other data by adding an IP header
What would larger networks connect to?
They will connect to Tier 2 networks through a Point of Presence (PoP)
Type / Length
This 2-byte field identifies the upper layer protocol encapsulated in the Ethernet frame. Common values are, in hexadecimal, 0x800 for IPv4, 0x86DD for IPv6 and 0x806 for ARP. Note: You may also see this field referred to as EtherType, Type, or Length
Source MAC Address Field
This 6-byte field identifies the originating NIC or interface of the frame. A source MAC address can only be a unicast address
Destination MAC Address Field
This 6-byte field is the identifier for the intended recipient. As you will recall, this address is used by Layer 2 to assist devices in determining if a frame is addressed to them. The address in the frame is compared to the MAC address in the device. If there is a match, the device accepts the frame. Can be a unicast, multicast or broadcast address
Access method
This determines when someone can send a message. Click Play in the figure to see an animation of two people talking at the same time, then a "collision of information" occurs, and it is necessary for the two to back off and start again. Likewise, when a device wants to transmit on a wireless LAN, it is necessary for the WLAN network interface card (NIC) to determine whether the wireless medium is available
Data Field
This field (46 - 1500 bytes) contains the encapsulated data from a higher layer, which is a generic Layer 3 PDU, or more commonly, an IPv4 packet. All frames must be at least 64 bytes long. If a small packet is encapsulated, additional bits called a pad are used to increase the size of the frame to this minimum size
Email Server
This server runs email server software that enables emails to be sent and received
Which tiers connect homes and businesses to the internet?
Tier 3
In computer communication, what is the purpose of message encoding?
To convert information to the appropriate form for transmission
A network administrator can successfully ping the server at www.cisco.com, but cannot ping the company web server located at an ISP in another city. Which tool or command would help identify the specific router where the packet was lost or delayed?
Traceroute
DNS (Domain Name System)
Translates domain names such as cisco.com, into IP addresses
At which OSI layer is a destination port number added to a PDU during the encapsulation process?
Transport Layer
The preamble field is not included when describing the size of the frame T/F?
True
What Wired communication tools does Ethernet use?
Twisted pair, fiber-optic links, and coaxial cables
Which Ethernet frame field describes the higher-layer protocol that is encapsulated?
Type/Length
SFTP (Secure File Transfer Protocol)
Used as an extension to Secure Shell (SSH) protocol, SFTP can be used to establish a secure file transfer session in which the file transfer is encrypted. SSH is a method for secure remote login that is typically used for accessing the command line of a device
