computer network

Internetworking

Connecting multiple independent networks using routers

Datagram

A self contained packet routed independently without setup

Connectionless Service

A service with no guarantees on delivery order or duplication

Best Effort Delivery

Network makes no guarantees about packet delivery

IP Address

A logical identifier assigned to a network interface

Network ID

The portion of an IP address identifying the network

Host ID

The portion of an IP address identifying the host

CIDR

Classless addressing that allows variable length prefixes

Subnetting

Dividing a network into smaller logical subnetworks

Subnet Mask

A bit mask separating network and host portions

Longest Prefix Match

Routing rule that selects the most specific matching route

Routing Table

A table mapping destination networks to next hops and interfaces

Next Hop

The next router to which a packet is forwarded

Outgoing Interface

The physical interface used to forward a packet

Default Route

A route used when no other match exists

ARP (Address Resolution Protocol)

Maps an IP address to a MAC address

ARP Request

A broadcast asking for the MAC address of an IP

ARP Reply

A unicast response containing the MAC address

ARP Cache

Stores recently resolved IP to MAC mappings

DHCP (Dynamic Host Configuration Protocol)

Automatically assigns IP configuration

DHCP Discover

Broadcast sent by a client to find DHCP servers

DHCP Offer

Server response offering an IP address

DHCP Request

Client request accepting the offer

DHCP Acknowledgment

Final confirmation of IP assignment

ICMP (Internet Control Message Protocol)

Used for error reporting and diagnostics

Echo Request

ICMP message used by ping

Echo Reply

ICMP response to echo request

Time Exceeded

ICMP error indicating TTL expiration

TTL (Time To Live)

Limits how many hops a packet can traverse

MTU (Maximum Transmission Unit)

Largest packet size a link can transmit

IP Fragmentation

Breaking packets into smaller pieces

Broadcast Address

An IP address with all host bits set to 1

Link Local Address

An address used only within a single link

Site Local Address

An address used within a private site

Distance Vector Routing

Routing based on exchanging distance vectors

Bellman Ford Algorithm

Algorithm used in distance vector routing

Count to Infinity

A slow convergence problem in distance vector routing

Split Horizon

A technique to prevent routing loops

Link State Routing

Routing based on flooding link state information

OSPF

A link state intra domain routing protocol

Dijkstra Algorithm

Computes shortest paths in link state routing

Autonomous System (AS)

A group of networks under one administration

Intra Domain Routing

Routing within a single autonomous system

Inter Domain Routing

Routing between autonomous systems

BGP (Border Gateway Protocol)

The inter domain routing protocol of the Internet

Path Vector Protocol

Advertises full paths to destinations

AS Path

List of autonomous systems a route has traversed

Policy Based Routing

Routing decisions based on policy

Hot Potato Routing

Routes traffic out of an AS as quickly as possible

Cold Potato Routing

Keeps traffic inside an AS as long as possible

Switch

Forwards frames based on MAC addresses

Bridge

Connects LAN segments and filters traffic

Hub

Broadcasts frames to all ports

MAC Address

A hardware address used at the data link layer

Learning Switch

Builds forwarding table by observing traffic

Forwarding Table

Maps MAC addresses to output ports

Spanning Tree Protocol

Prevents loops in switched networks

Broadcast Storm

Excessive broadcast traffic due to loops

Transport Layer

Provides end to end process communication

Multiplexing

Multiple applications sharing the network

Demultiplexing

Delivering data to the correct application

UDP (User Datagram Protocol)

Unreliable and connectionless transport protocol

UDP Checksum

Optional error detection mechanism

UDP Port

Identifies an application endpoint

TCP (Transmission Control Protocol)

Reliable and connection oriented protocol

Reliable Delivery

Guarantees correct and ordered delivery

Byte Stream Service

Delivers data as a continuous stream

Sequence Number

Identifies byte position in TCP stream

Acknowledgment Number

Indicates next expected byte

Sliding Window

Controls how much data can be in transit

Flow Control

Prevents sender from overwhelming receiver

Congestion Control

Prevents overwhelming the network

Three Way Handshake

TCP connection setup using SYN SYN ACK

SYN Flag

Initiates a TCP connection

FIN Flag

Gracefully terminates a TCP connection

RST Flag

Abruptly terminates a TCP connection

Send Buffer

Stores unacknowledged transmitted data