Chapter3 Cisco

Three core elements of communication

Sender (source), receiver (destination), and transmission media/channel (physical cable or wireless path)

Message encoding vs. message decoding

Encoding converts computer data into electrical/radio signals for transmission; decoding converts those signals back into data at the receiver

Three key components of network message timing

Flow control (transmission speed), response timeout (wait time for replies), and access method (rules preventing packet collisions)

Collision and proactive vs. reactive access methods

A collision is corrupted data when two devices talk at once; proactive methods avoid collisions before sending (CSMA/CA), while reactive methods detect and recover after they occur (CSMA/CD)

Unicast, Multicast, and Broadcast delivery methods

Unicast is one-to-one; Multicast is one-to-a-specific-group; Broadcast is one-to-all devices on the local network

Broadcast transmission support in IPv6

False; IPv6 completely removes broadcast addresses and replaces them with multicast and anycast

Implementation of network protocols on devices

Implemented in software (operating systems/drivers), hardware (network cards/chips), or a combination of both

Four primary types of network protocols

Communication (basic data transfer), Security (encryption/authentication), Routing (finding best network paths), and Service Discovery (automatically finding network devices)

Six primary functions of network protocols

Addressing, reliability (guaranteed delivery), flow control, sequencing (ordering chunks), error detection, and application interfacing

Protocol roles in a web conversation (HTTP, TCP, IP, Ethernet)

HTTP requests the web page; TCP ensures reliable packet delivery; IP routes packets globally across networks; Ethernet transmits frames locally between NICs on the LAN

Definition of a network protocol suite

An organized stack of layered protocols designed to work together to handle end-to-end communication

Four historical protocol suites and modern dominant standard

TCP/IP is the open global standard today; AppleTalk, Novell NetWare, and OSI are obsolete historical suites

Four layers of the TCP/IP model

Application (top), Transport, Internet, and Network Access (bottom)

TCP/IP Application layer protocols

High-level services: DNS (naming), DHCP (auto-IP), HTTP/HTTPS (web), SMTP/POP3/IMAP (email), and FTP/SFTP (file transfer)

TCP vs. UDP at the TCP/IP Transport layer

TCP is connection-oriented, sequenced, and resends lost packets; UDP is connectionless, fast, and does not guarantee delivery

TCP/IP Internet layer protocols

Routable network protocols: IPv4, IPv6, NAT (address translation), ICMP (ping/diagnostics), and dynamic routing (OSPF, EIGRP, BGP)

TCP/IP Network Access layer protocols

Local link delivery: ARP (maps IP to MAC), Ethernet (IEEE 802.3 wired), and WLAN (IEEE 802.11 Wi-Fi)

Benefits of open networking standards

Allows hardware from different vendors to work together (interoperability), prevents monopolies, and drives competition

Roles of ISOC, IAB, IETF, and IRTF

ISOC promotes open internet; IAB oversees standards; IETF (Internet Engineering Task Force) creates TCP/IP protocols/RFCs; IRTF researches long-term future tech

Responsibilities of ICANN and IANA

ICANN sets global policy for domains and IP spaces; IANA handles the direct technical assignment of IP blocks, domain registries, and port numbers

Standards governed by IEEE, EIA, and TIA

IEEE sets LAN/wireless standards (802.3 Ethernet, 802.11 Wi-Fi); EIA sets physical hardware/rack specs; TIA standardizes telecom and network cabling pinouts

Focus of ITU-T standards

International telecom standards, broadband technologies like DSL, and video/audio compression

Seven layers of the OSI model (Layer 1 to Layer 7)

Layer 1 Physical, Layer 2 Data Link, Layer 3 Network, Layer 4 Transport, Layer 5 Session, Layer 6 Presentation, Layer 7 Application

Primary functions of OSI Layers 7, 6, and 5

Layer 7 (Application) interfaces with user software; Layer 6 (Presentation) formats, encrypts, and compresses data; Layer 5 (Session) establishes and manages active connections

Primary functions of OSI Layers 4, 3, 2, and 1

Layer 4 (Transport) segments data and manages flow control; Layer 3 (Network) routes packets with IP addresses; Layer 2 (Data Link) delivers frames using MAC addresses; Layer 1 (Physical) transmits bits over copper, fiber, or radio

OSI Model to TCP/IP Model mapping

OSI 7, 6, 5 map to TCP/IP Application; OSI 4 maps to Transport; OSI 3 maps to Internet; OSI 2 and 1 map to Network Access

Benefits of message segmentation

Allows multiplexing (sharing one wire across multiple conversations) and ensures only lost chunks need retransmission instead of the whole file

Definition of multiplexing

Interleaving multiple separate data streams together across a single shared transmission medium simultaneously

Definition of a Protocol Data Unit (PDU)

The specific name given to a data package at a particular layer after its headers and trailers have been added

TCP/IP Protocol Data Units (PDUs) in top-down order

Data (Application) -> Segment (Transport) -> Packet (Internet) -> Frame (Network Access) -> Bits (Physical)

Encapsulation vs. De-encapsulation

Encapsulation is top-down (adding headers/trailers to send data); de-encapsulation is bottom-up (stripping headers off as the receiver reads data)

Structural parts of an IP address

Network portion (or IPv6 Prefix) identifies the subnet; Host portion (or IPv6 Interface ID) uniquely identifies the individual device on that subnet

Destination addressing on the same local network

Destination IP is the local host's IP; Destination MAC is the local host's physical network card address

Destination addressing when routing to a remote network

Destination IP is the final remote server's IP (stays constant); Destination MAC is the local router's default gateway MAC address

Role of the Default Gateway

The local router interface IP that acts as the exit door for traffic heading to any remote network outside the local subnet

Address behavior across multiple router hops

Layer 3 IP addresses stay unchanged from start to finish; Layer 2 MAC addresses are stripped and rewritten at every router hop along the path