Comprehensive Notes on Networking Cabling and Communication

Cabling Fundamentals

• Cabling forms the fundamental communication pathway in a network.

• Choosing the right cable is crucial, especially in new setups like data centers.

• Wired connections remain the primary mode of network communication despite the prevalence of wireless networks.

Twisted Pair Copper Cabling

• Commonly used in Ethernet networks.

• Consists of four pairs of wires, each with different colors (blue, green, orange, brown, and their respective whites).

• Pairs carry equal and opposite signals (transmit plus and transmit minus).

• Twisting the cables reduces interference, as the signal constantly moves away from interference.

• The signals are compared at the receiving end to identify and mitigate interference.

• Each pair has a different twist rate to further differentiate signals and reduce interference.

Categories of Twisted Pair Cables

• Different categories have varying electrical characteristics and support different networks.

• Ethernet standards specify minimum cable category requirements.

• 1000BASE-T:

  • A one gigabit per second Ethernet standard.

  • Minimum category 5 cabling, up to 100 meters.

• Category 5e (Enhanced):

  • Category 5 cable with additional validation tests.

  • Commonly available for new installations.

• 10GBASE-T:

  • A 10-gigabit per second Ethernet standard.

  • Supports Category 6A up to 100 meters.

Coaxial Cable

• Features two or more forms sharing a common axis.

• Components:

  • A central wire conductor.

  • Insulator surrounding the conductor.

  • Metal shielding.

  • Outer plastic jacket.

• Commonly used for cable television and cable modem connections in homes.

• Typically uses RG-6 coax cable.

Plenum Rated Cables

• Plenum: Shared airspace often used for air return and network cables.

• Standard Ethernet cables typically use PVC (polyvinyl chloride) jackets.

• Plenum-rated cables are essential for plenum spaces to prevent toxic fumes during fires.

• Plenum cables use FEP (fluorinated ethylene polymer) or low-smoke PVC.

• Plenum cables may be less flexible but are safer in fires.

Shielding

• UTP (Unshielded Twisted Pair): No special shielding.

• STP (Shielded Twisted Pair): Shielding around the entire cable or individual wires.

• Shielded cables often include a grounding wire.

• Cable markings indicate shielding type using abbreviations:

  • U: Unshielded

  • S: Braided Shielding

  • F: Foil Shielding

  • TP: Twisted Pair

• Examples:

  • S/FTP: Braided shielding around the entire cable and foil around the pairs.

  • F/UTP: Foil around the entire cable, unshielded pairs inside.

  • F/FTP: Braided shield and foil around the entire cable, foil around individual pairs.

Direct Burial STP

• Designed for outdoor use, often buried directly in the ground.

• Features:

  • Waterproofing.

  • Gel filling to protect against moisture.

  • Shielded twisted pair construction for interference protection and added strength.

  • Drain wire to remove voltages through a ground wire.

Communication Types

Unicast

• One-to-one communication between devices.

• Used for web server connections and file transfers.

• Common in both IPv4 and IPv6.

• Inefficient for simultaneous communication to multiple devices.

Broadcast

• One device sends information to all devices on the network.

• Efficient for the source device but can create performance issues with many broadcasts.

• Limited to the local IP subnet (broadcast domain).

• Used by routing protocols and ARP requests in IPv4.

Multicast

• Sends a single frame to interested devices only.

• Used for multimedia, stock tickers, and intelligent routing protocol updates.

• Requires careful engineering for larger networks.

• Common in IPv4 and extensively used in IPv6 (as IPv6 lacks broadcast).

Anycast

• Communication to a single device out of many available options.

• Devices have the same unicast (Anycast) address and respond to requests.

• Used on the Internet to distribute servers geographically (e.g., DNS root servers).

Network Models

Peer-to-Peer

• Every device acts as both server and client.

• Easy to deploy without a dedicated server.

• Low implementation cost.

• Difficult to administer and secure due to distributed nature.

Client-Server

• Clients access data from a centralized server.

• Centralized application and authentication management.

• Requires additional hardware and software for the server.

Network Types

Local Area Network (LAN)

• Network within a single building or local area.

• High-speed throughput via Ethernet or 802.11 wireless.

Metropolitan Area Network (MAN)

• Larger network spanning a citywide area.

• Often involves a third-party provider.

• Commonly used by governments.

Wide Area Network (WAN)

• Network over a large geographic distance.

• Generally slower throughput than LANs.

• Connections via MPLS, point-to-point serial, fiber, or satellite.

Wireless Local Area Network (WLAN)

• Wireless network within a limited area (building).

• Based on 802.11 standards.

• Multiple access points can extend the range.

Personal Area Network (PAN)

• Personal connection between devices.

• Examples: Bluetooth headsets, Bluetooth car audio systems, connections to workout equipment.

Campus Area Network (CAN)

• Connects multiple buildings on a campus.

• High-speed Ethernet connections, often using private conduit and fiber.

Data Storage Networks

Network Attached Storage (NAS)

• Centralized storage device with multiple drives.

• File-level access: Changes require overwriting the entire file.

Storage Area Network (SAN)

• Provides block-level access to data.

• Faster and more efficient for making small changes compared to NAS.

• Often uses a dedicated network for high-speed data transfer.

Wide Area Network Technologies

Multi-Protocol Label Switching (MPLS)

• Uses labels to route traffic through the WAN.

• Supports various connection types and data formats (IP, Ethernet).

• Forwarding decisions based on label switching.

  • Edge router pushes a label onto data.

  • Label directs traffic through the provider network.

  • Label is popped off at the destination.

Dynamic Multipoint VPN (DMVPN) with Multipoint Generic Routing Encapsulation (MGRE)

• Creates dynamic network connections only when needed.

• VPN can rebuild itself if there are connection breaks.

• Creates a dynamic mesh network for efficient data transfer between sites.

Software-Defined Wide Area Network (SD-WAN)

• WAN defined by software to optimize routing.

• Useful for cloud-based applications.

• Directs traffic based on the type of data, avoiding unnecessary hops through a central data center.

Network Configuration Examples

Small Office/Home Office (SOHO)

• Internet connection, router, switch, and wireless access point.

• Devices connect via wired Ethernet or wireless.

Enterprise Network

• Complex networks with many users and devices across multiple floors or buildings.

• Core switches connect to switches on different floors.

Ethernet Frame

• Structure of an Ethernet frame to understand how traffic is transmitted.

  • Preamble (7 bytes): Alternating ones and zeros to notify devices of an incoming Ethernet frame.

  • Start Frame Delimiter (1 byte): Designates the end of the preamble and the start of the frame.

  • Destination MAC Address (6 bytes): Destination of the Ethernet frame.

  • Source MAC Address (6 bytes): Origin of the Ethernet frame.

  • EtherType Field (2 bytes): Describes the type of data in the Ethernet frame.

  • Payload (46-1500 bytes): Contains Layer 3 data (e.g., IP traffic).

  • Frame Check Sequence (FCS) (4 bytes): Cyclic redundancy check to ensure data integrity.

MAC Addresses

• Media Access Control (MAC) address is the physical address of an Ethernet adapter.

• Unique for every device.

• Six bytes (48 bits) long, represented in hexadecimal.

• Example: 8C:2D:AA:4B:98:A7

• Organizationally Unique Identifier (OUI): First three bytes, indicating the manufacturer.

• Network Interface Controller Specific Value: Last three bytes, acting as a serial number for the adapter.

Duplex Communication

Half Duplex

• Devices can only send or receive data at one time.

• Used with Ethernet hubs.

• Prone to collisions when two devices transmit simultaneously.

Full Duplex

• Devices can send and receive data simultaneously.

• Commonly used with switches.

• Provides higher throughput compared to half-duplex.

CSMA/CD (Carrier Sense Multiple Access with Collision Detection)

• Used in half-duplex Ethernet to manage collisions.

• Carrier Sense (CS): Detects if the network is in use.

• Multiple Access (MA): Multiple devices on the same network.

• Collision Detect (CD): Detects collisions and triggers retransmission.

Collision Detection Process

• Device listens to the network.

• If clear, the device sends traffic.

• Simultaneous transmissions cause a collision.

• Devices send a jam signal.

• Devices wait a random time and retransmit.

Full Duplex Network Operation With Switches

• Switch examines the destination MAC address to forward the frame directly to the destination.

• No flooding of frames.

• Simultaneous sending and receiving of data without collisions.