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Questions and Answers
Which organization created the Open Systems Interconnection (OSI) reference model to standardize network connectivity?
The OSI model has __ layers.
7
Changing a network protocol at one layer in the OSI model will impact the other layers.
False
What is the purpose of the OSI model in network communications?
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Which layer of the OSI model is responsible for encryption/decryption, translation, and compression/decompression?
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The Transport layer (layer 4) is where TCP/IP operates.
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What is the purpose of the Data Link layer (layer 2) in the OSI model?
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The __________ layer (layer 3) is responsible for the logical numbering of hosts and networks.
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Which protocol is responsible for all data delivery and has all the bells and whistles for a developer?
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TCP is slower than UDP.
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What does TCP stand for?
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The maximum transmission unit for Ethernet is ______ bytes.
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What is the responsibility of the LLC layer in the Data Link layer?
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What is the purpose of the MAC layer in the Data Link layer?
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The MAC layer saves CPU cycles by processing checks independently from the CPU and the operating system.
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The ______ field is responsible for carrying the protocol number for which traffic is destined.
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Match the following components with their responsibilities:
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What is the main purpose of MPLS in a network?
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MPLS is considered to be a layer 2.5 protocol.
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What does SDWAN stand for?
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___ is used to create a virtual tunnel over the Internet or an internetwork.
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Match the networking component with its description:
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What is the formula to calculate how many connections are needed to achieve a full mesh between four switches?
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Which of the following statements is true about bus networks?
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A WAN is always faster than LAN speeds.
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A ______________ is a network reserved for storage access.
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What is the function of a virtual network interface card (vNIC)?
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What unique features does the VMware VMXNET3 NIC support?
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Virtual firewalls installed as virtual machines can benefit from the fault tolerance of the entire virtualization cluster.
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______ is a virtual router offered by Cisco and supported by cloud providers such as Amazon and Microsoft Azure.
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Match the following service types with their descriptions:
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What are the two main media types used for wiring a network?
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Which type of cabling is the most common for Ethernet networks today?
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Coaxial cable is still commonly used for Ethernet communications on the LAN.
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STP cables should be used in settings where ______ can induce erroneous data into the cable.
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What is the download speed of Symmetrical Digital Subscriber Line (SDSL)?
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SDSL is more expensive than leased lines.
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What does VDSL stand for?
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Broadband cable operates on a specification called Data Over Cable Service Interface Specification (________).
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Match the following terminologies with their descriptions:
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Study Notes
Domain 1.0: Networking Fundamentals
OSI Model
- The OSI model is a 7-layered framework for network communication
- Created by the International Organization for Standardization (ISO) to standardize network connectivity between applications, devices, and protocols
- Allows for interoperability between different vendors
- Divides a complex communication process into smaller pieces to assist with design, development, and troubleshooting
OSI Model Layers
Application Layer (Layer 7)
- Provides the user interface to the user and often the beginning of the communication process
- Defines the role of the application, as either a client or server
- Examples of application layer events:
- Sending email
- Remote access
- File transfer
- Instant messenger
- VoIP calls
Presentation Layer (Layer 6)
- Presents data to the Application layer
- Responsible for:
- Encryption/decryption
- Translation
- Compression/decompression
- Examples of translation services:
- Converting Extended Binary Coded Decimal Interchange Code (EBCDIC) data to American Standard Code for Information Interchange (ASCII)
- Converting ASCII to Unicode
- Examples of compression and decompression:
- MP3 to network streaming protocols
- H.264 video to streaming protocols
- JPEG, GIF, PICT, and TIFF image formats
Session Layer (Layer 5)
- Responsible for the setup, management, and teardown of a session between two computers
- Dialogue control:
- Half-duplex: two-way communication where only one side can communicate at a time
- Full-duplex: two-way communication where both sides can communicate simultaneously
- Simplex: one-way communication
Transport Layer (Layer 4)
- First layer responsible for maintaining network communication
- Protocols: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)
- Operating system presents the application with a socket to communicate with on the network
- Port numbers:
- Server application binds to a port
- Client application dynamically allocates a port number above 1023
Other Networking Concepts
Network Topologies and Types
- Mesh
- Star/hub-and-spoke
- Bus
- Ring
- Hybrid
- Network types:
- Peer-to-peer
- Client-server
- LAN
- MAN
- WAN
- WLAN
- PAN
- CAN
- SAN
- SDWAN
- MPLS
- mGRE
Cables and Connectors
- Copper:
- Twisted pair (Cat 5, Cat 5e, Cat 6, Cat 6a, Cat 7, Cat 8)
- Coaxial (RG-6)
- Twinaxial
- Fiber:
- Single-mode
- Multimode
- Connector types:
- Local connector (LC)
- Straight tip (ST)
- Subscriber connector (SC)
- Mechanical transfer (MT)
- Registered jack (RJ)
- Transceivers/media converters:
- Small form-factor pluggable (SFP)
- Enhanced form-factor pluggable (SFP+)
- Quad small form-factor pluggable (QSFP)
- Enhanced quad small form-factor pluggable (QSFP+)
IP Addressing and Subnetting
- IPv4 vs. IPv6
- Private vs. public addresses
- Network address translation (NAT) and port address translation (PAT)
- Subnetting:
- Classless (variable-length subnet mask)
- Classful (A, B, C, D, E)
Network Services
- DHCP:
- Scope
- Exclusion ranges
- Reservation
- Dynamic assignment
- Static assignment
- Lease time
- Scope options
- DNS:
- Record types (A, CNAME, MX, AAAA, SOA, PTR, TXT, SRV, NS)
- Global hierarchy (root DNS servers, internal vs. external)
- Zone transfers
- Authoritative name servers
- Time to live (TTL)
- DNS caching
- Reverse DNS/reverse lookup/forward lookup
- Recursive lookup/iterative lookup
Corporate and Datacenter Network Architecture
- Three-tiered architecture:
- Core
- Distribution/aggregation layer
- Access/edge
- Software-defined networking:
- Application layer
- Control layer
- Infrastructure layer
- Management plane
- Spine and leaf architecture
- Traffic flows:
- North-South
- East-West
- Branch office vs. on-premises datacenter vs. colocation
- Storage area networks (SANs)
- Connection types (FCoE, Fibre Channel, iSCSI)
Cloud Concepts and Connectivity Options
- Deployment models:
- Public
- Private
- Hybrid
- Community
- Service models:
- SaaS
- IaaS
- PaaS
- DaaS
- Infrastructure as code:
- Automation/orchestration
- Connectivity options:
- VPN
- Private-direct connection to cloud provider
- Multitenancy
- Elasticity
- Scalability
- Security implications### Transport Layer
- The client binds to port numbers 1024, 1025, and 1026 to send requests to the web server on port 80.
- The web server responds with the source port number 80 to the destination port numbers 1024, 1025, and 1026 on the client.
- The client then passes the data to the web page via the incoming data on the respective port number.
- Once the client receives the information, both the client and server close the session for the port and the port can be recycled.
UDP and TCP
- UDP (User Datagram Protocol) is a transport protocol for TCP/IP that is connectionless, meaning it does not guarantee delivery of data.
- UDP is faster than TCP but lacks reliability features.
- TCP (Transmission Control Protocol) is a transport protocol for TCP/IP that is connection-oriented, guaranteeing delivery of data.
- TCP is slower than UDP but provides reliability features such as sequencing, acknowledgment, and retransmission.
Network Layer
- The Network layer (layer 3) is responsible for logical numbering of hosts and networks.
- The Network layer is also responsible for transporting data between networks through the process of routing.
- Routers operate at the Network layer to facilitate the movement of packets between networks.
- IP (Internet Protocol) is a Network layer protocol that allows for logical addressing of networks and hosts.
- IP addresses are used to route packets to the appropriate destination.
Data Link Layer
- The Data Link layer (layer 2) is responsible for framing of data for transmission on the Physical layer.
- The Data Link layer is also responsible for static addressing of hosts using MAC (Media Access Control) addresses.
- MAC addresses are preprogrammed into network cards and network interfaces.
- The Data Link layer is only concerned with local delivery of frames in the same immediate network.
- Switches operate at the Data Link layer, switching frames between networks.
Physical Layer
- The Physical layer is responsible for transmitting the data as 1s and 0s that is passed down from the Data Link layer.
- The Physical layer is an integral component of many different types of transmission methods such as wireless, fiber optics, and Ethernet.
Protocol Data Units (PDUs)
- PDUs are used to describe the type of data transferred at each layer of the OSI model.
- The layers of the OSI model and their corresponding PDUs are:
- Application, Presentation, and Session layers: user datagrams (datagrams)
- Transport layer: segments
- Network layer: packets
- Data Link layer: frames
- Physical layer: bits
Data Encapsulation and Decapsulation
- Data encapsulation is the process of passing a PDU down to the next layer in the protocol stack, adding information to the PDU header or type field.
- Data decapsulation is the process of passing the payload (data) up to the next layer in the protocol stack, reading the information from the PDU header or type field.
- Encapsulation and decapsulation occur at each layer of the OSI model, with each layer adding or removing information from the PDU.
IP Packet Header
- The IP packet header contains fields such as:
- Version (4 bits): indicates the version of IP (IPv4 or IPv6)
- Priority and type of service (ToS) (8 bits): used for quality of service (QoS)
- Time to live (TTL) (8 bits): used for routing to prevent endless routing
- Protocol (8 bits): defines where to send the data next (UDP, TCP, ICMP, etc.)
- Source and destination IP addresses (32 bits each): used for routing to the destination computer and responding to the destination computer.### Network Fundamentals
- The data being transferred is also known as the payload of the frame.
- The MTU (Maximum Transmission Unit) for Ethernet is 1500 bytes.
- The MTU can be increased to 9000 bytes, which is considered a jumbo frame.
- The MTU is a constraint on the Network layer, but it's usually adjustable only at the Data Link layer.
OSI Model
- The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
- Each layer has a specific function:
- Application layer: defines applications and services
- Presentation layer: converts data formats, encrypts and decrypts, and compresses data
- Session layer: sets up, maintains, and tears down communications
- Transport layer: responsible for flow control and error detection
- Network layer: assigns and routes network and host addresses
- Data Link layer: frames data for transmission
- Physical layer: transmits data via physical media
Protocol Data Units (PDUs)
- PDUs are used to describe payloads of data at each layer of the OSI model.
- PDUs help network professionals avoid miscommunication and clarify the data being transmitted.
Encapsulation and Decapsulation
- Encapsulation: the process of passing data down the protocol stack, adding headers and trailers at each layer.
- Decapsulation: the reverse process of encapsulation, removing headers and trailers at each layer.
TCP and UDP
- TCP (Transmission Control Protocol) is a connection-based protocol that uses SYN and ACK flags to establish a virtual communication circuit.
- UDP (User Datagram Protocol) is a connectionless protocol that uses a simple, 8-byte header.
- Both TCP and UDP use port numbers to direct information to the destination service.
Network Topologies
- There are two main types of topologies: physical and logical.
- Physical topology defines the physical connections between devices.
- Logical topology defines how the data flows through the network.
Wired Topologies
- Star topology: all devices are connected to a central hub or switch.
- Ring topology: devices are connected in a circular configuration, with data passing around the ring.
- Mesh topology: each device is connected to every other device, providing redundant connections.
- Bus topology: a legacy topology that used coaxial cables and is now considered deprecated.
Hybrid Topology
- A hybrid topology combines multiple topologies for resiliency, load balancing, and connectivity.
Network Types
- LAN (Local Area Network): a company's internal network, locally managed and optimized for speed.
- WAN (Wide Area Network): a network that interconnects multiple locations, often over a wide area.
- WLAN (Wireless Local Area Network): a wireless extension of a LAN.
- MAN (Metropolitan Area Network): a type of WAN that connects multiple locations within a defined geographical area.
- CAN (Campus Area Network): a network that connects multiple buildings or LANs, locally managed.
- SAN (Storage Area Network): a dedicated network for storage access, often using Fibre Channel technology.
- PAN (Personal Area Network): a small network for personal use, often using Bluetooth or other wireless technologies.
Other Network Technologies
- MPLS (Multiprotocol Label Switching): an emerging WAN technology that uses packet-switching and labeling.
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