Overview of Routing and Network Protocols

Instance Vector Routing Protocols

A routing family that uses vector-based metrics to pick best paths; examples: RIP, IGRP

Dynamic Routing Protocols

Protocols that automatically learn & update routes as topology changes; e.g., RIP, OSPF, EIGRP

Two Classes (Routing Protocols)

The two broad categories: IGP (Interior Gateway Protocols) and EGP (Exterior Gateway Protocols)

IGP (Interior Gateway Protocol)

Routing protocols used within a single autonomous system

EGP (Exterior Gateway Protocol)

Routing protocols used between autonomous systems

BGP (Border Gateway Protocol)

The de-facto EGP that exchanges reachability info among autonomous systems on the Internet

Routing Table

Router data structure listing destination networks, metrics, and next-hop interfaces

Routing by Rumors

Ad-hoc "gossip" style routing where nodes exchange informal updates without a formal protocol

Directly Connected Network

Network reachable via a router's own interface; no further routing needed

Static Route

Manually configured, unchanging route in the routing table

Dynamic Route

Route learned and updated automatically by a routing protocol

Routing Speed

Time a router takes to process a packet and make a forwarding decision

Routing Responsiveness

How quickly a router updates its table after a topology change

Stability (Network)

The ability of a network to maintain consistent, uninterrupted connectivity

Security (Network)

Measures that protect the network from unauthorized access and attacks

Distance Vector

Algorithm where routers share distance metrics with neighbors; path cost often hop count

Static NAT

One-to-one mapping between a private IP and a public IP

Dynamic NAT

Many-to-many mapping that draws from a pool of public IPs on demand

Port Forwarding

NAT rule that forwards traffic for a public IP:port to a specific internal IP:port

Public IP Address

Globally routable Internet address assigned by ISPs or RIRs

IP Masquerading

NAT technique letting many private hosts share one public IP by rewriting source info

Host Portion (of IP)

Bits of an IP address identifying the specific device within a subnet

Subnet Mask

32-bit mask that separates network bits from host bits in an IP address

Network Classes

Traditional IPv4 groupings: Class A, B, C, D (multicast), E (reserved)

Multiple Access

Capability of multiple nodes to share the same communication medium

Single Shared Broadcast Channel

Common channel where any node's frame is heard by all others

Interference

Signal overlap from simultaneous transmissions that corrupts data

Collision

When two frames transmit at once on a shared medium and interfere

MAC (rate R bps)

Shared medium with capacity R bits per second available to all nodes

FDMA (Frequency Division Multiple Access)

Channel-partitioning MAC that assigns users distinct frequency sub-bands

Random Access Protocol

No centralized control; nodes contend for the medium (e.g., ALOHA, CSMA)

Slotted ALOHA

Random access protocol where transmissions start only at slot boundaries

Frame Size

Total length of a data frame, including headers and trailers

CSMA

Carrier Sense Multiple Access: listen before transmit to reduce collisions

CSMA/CD

Ethernet method that senses and detects collisions, then backs off before retrying

Parity Check

1-bit error-detection scheme that counts ones or zeros in data

Even Parity

Parity bit set so total number of ones is even

Two-Dimensional Parity

Row- and column-based parity that can detect and correct single-bit errors

Internet Checksum

Simple summation method for error detection in IP, TCP, UDP headers

CRC (Cyclic Redundancy Check)

Error-detection technique used to detect changes to raw data

CRC (Cyclic Redundancy Check)

Polynomial-based error detection capable of catching many bit errors

Binary Division

Mathematical operation used to compute CRC remainders

Link Layer

OSI layer handling node-to-node delivery over a single link (framing, MAC, etc.)

Ethernet

Wired LAN tech using CSMA/CD; defines physical and data-link specs

VLAN (Virtual LAN)

Logical segmentation that isolates traffic within the same physical switch

MPLS

Link-layer-like label switching that speeds routing and enables traffic engineering

Wi-Fi Signals

Radio waves that carry IEEE 802.11 wireless LAN traffic

Signal Attenuation

Reduction in signal strength over distance or through obstacles

Multipath Interference

Signal copies arriving via different paths interfere constructively/destructively

SNR (Signal-to-Noise Ratio)

Difference between received signal power and noise floor

BER (Bit Error Rate)

Fraction of received bits that are corrupted; quality metric for a link

SNR-BER Trade-off

Higher SNR generally lowers BER; higher bit rates raise BER unless SNR increases

CDMA

Code Division Multiple Access; devices share band using unique spreading codes

802.11b

2.4 GHz Wi-Fi up to 11 Mb/s

802.11g

2.4 GHz Wi-Fi up to 54 Mb/s with OFDM

802.11n

2.4/5 GHz Wi-Fi with MIMO; up to ~600 Mb/s

802.11ac

5 GHz Wi-Fi with wider channels/MU-MIMO; gigabit-class speeds

802.11af

TV-white-space Wi-Fi ("Super Wi-Fi") for long-range low-frequency use

802.11ah

Sub-GHz IoT-oriented Wi-Fi for long-range, low-power sensors

Eavesdrop

Unauthorized intercept of network traffic

Message Insertion

Attacker injects packets into an existing connection

Impersonation (Spoofing)

Forging a device or user identity on the network

Hijacking

Seizing control of a network session or traffic flow

Denial of Service (DoS)

Attack that makes a service unavailable by flooding or resource exhaustion

Local Network (LAN)

Internal network within a limited geographic area (home, office, campus)

Out-of-Band Management

Separate path used exclusively for remote device administration

Rack Elevation

Vertical placement of equipment in a data-center rack

Rack Switch

In-rack switch distributing network to servers in that rack

Demarcation Point

Boundary where provider responsibility ends and customer's begins

Network Encryptor

Appliance or software that encrypts traffic between endpoints

Rack

Standardized frame for mounting servers, switches, and other IT gear

PDU (Power Distribution Unit)

Device that distributes power to rack-mounted equipment

APC

Brand known for UPS, PDUs, and power-management products

Network Cabling

Physical media (copper, fiber) that carries data signals

KVM Switch

Device enabling one keyboard/video/mouse to control multiple servers

ILO / ILM

Integrated Lights-Out/Management for remote server console & power control

F5 Load Balancer

Appliance that spreads client requests across servers for performance & HA

Fiber Connection

High-speed optical link offering high bandwidth and long reach

Copper Connection

Ethernet cabling using copper conductors (e.g., Cat 5e/6)

Error Detection & Correction

Techniques that find and fix bit errors in transmitted data

Sharing a Broadcast Channel

MAC methods that let multiple nodes use one medium efficiently

Link-Layer Addressing

Use of MAC addresses in frame headers to ID source and destination

Framing & Link Access

Encapsulating datagrams in frames and controlling medium access

Reliable Link Delivery

Ensuring in-order, error-free delivery between directly connected nodes

Half-Duplex

Link mode where a node transmits or receives, but not both at once

Full-Duplex

Link mode allowing simultaneous bidirectional transmission