Chapter 11: Networking Fundamentals Flashcards
protocol
set of rules dictate how computers communicate over networks
Layer 7
application layer; services and protocols required by user’s applications for networking functionality
Layer 6
presentation layer; standardizes data format and deals with syntax of data, not the meaning
Layer 5
session layer; sets, maintains, and breaks down the dialog (session) between two applications; controls the dialog organization and synchronization
Layer 4
transport layer; provides end-to-end encryption
Layer 3
network layer; routing, addressing, and fragmentation of packets; can determine alternative routes to avoid network congestion; where routers work
Layer 2
Data link layer; prepares data for the network medium by framing it; where the different LAN and WAN technologies work
Layer 1
physical layer; provides physical connections for transmission and performs the electrical encoding of data; transforms bits to electrical signals
network topology
the arrangement of computers and devices
bus topology
a single cable runs the entire length of the network and nodes attach to it through drop points
star topology
all nodes connect to a central device like a switch using a dedicated link
mesh topology
all nodes are connected to each other in a non-uniform manner which provides multiple paths to most or all the nodes on the network
ring topology
a series of devices connect by unidirectional transmission links and form a closed loop that does not connect to a central system
Ethernet uses …
CSMA/CD
CSMA/CD
all computers compete for a shared network cable, listen to learn when they can transmit data and are susceptible to data collisions
Token Ring
IEEE 802.5; an older LAN implementation which uses a token-passing technology
FDDI
A LAN and MAN tech; used for backbones; which used token-passing tech and has redundant rings in case the primary ring goes down
TCP/IP
suite of protocols which is the de facto standard for transmitting data across the Internet
TCP
reliable, connection-oriented protocol
IP
unreliable, connectionless protocol
Encapsulation
each layer add its own information as data travels down the network stack on the source computer; the process is reversed on the destination computer so the corresponding layer knows how to process the data
Two main protocol at the transport layer
TCP and UDP
UDP
connectionless protocol which does not send or receive acknowledgments when a datagram is received; does not ensure data arrives at its destination; provides “best-effort” delivery
TCP
connection-oriented protocol which sends and receives acknowledgments; ensures data arrives at the destination
ARP
translates the IP address into a MAC address (physical Ethernet address)
RARP
translates a MAC address into an IP address
ICMP
works at the network layer; informs hosts, routers, and devices of network or computer problems; major component of the ping utility
DNS
resolves hostnames into IP addresses and has distributed databases all over the Internet to provide name resolution
ARP poisoning
altering an ARP table so an IP address is mapped to a different MAC address; can redirect traffic to an attacker’s computer or an unattended system
Routers
link two or more network segments, where each segment functions as an independent network; work at the network layer with IP addresses, and have more network knowledge than bridges, switches, or repeaters
IPv4
32 bits for its addresses
IPv6
128 bits for its addresses; provides more possible addresses with which to work
NAT
used when orgs do not want systems to know internal hosts’ addresses and enables orgs to use private, nonroutable IP addresses
subnetting
allows large IP address ranges to be divided into smaller, logical, and easier-to-maintain network segments
dedicated links
the most expensive type of WAN connectivity method because the fee is based on the distance between the two destinations rather than on the amount of bandwidth used
dedicated link examples
T1 and T3
Frame relay and X.25
packet-switched WAN technologies which use virtual circuits instead of dedicated ones
ATM
transfers data in fixed cells, WAN technology, and transmits data at very high rates; supports voice, data, and video applications
circuit-switching technology
set up a circuit to be used during data transmission sessions
packet-switching technologies
do not set up circuits; packets travel along many different routes to arrive at the same destination
Three main types of multiplexing
statistical time division, frequency division, and wave division
Access layer
connects the customer’s equipment to a service provider’s aggregation network
Aggregation
occurs on a distribution network
metro layer
metropolitan area network
Systems built on the OSI model are considered … systems
open
Open system built on the OSI model means
built with internationally accepted protocols and standards so they can easily communicate with other systems
networking stack
conceptual model to describe where different functionalities take place and where different protocols live and carry out those specific functions; OSI model helps describe the networking stack with 7 layers
Protocol::Layer ARP::…
Data Link; Layer 2
Protocol::Layer IP::…
Network Layer; Layer 3
Protocol::Layer UDP:: …
Transport; Layer 4
Protocol::Layer TFTP:: …
Application; Layer 7
what happens in data link layer
layer 2 is where framing happens; only layer that understands the environment in which the system is working: Ethernet, Token Ring, wireless, connection to a WAN link; adds necessary headers and trailers to the frame; other systems on the same type of network using the same technology understand only the specific header and trailer format used in their data link technology
what happens at the session layer
diaglog control; layer 5 is responsible for controlling how applications communicate (not all applications use protocols that work at the session layer so this layer is not always used in networking functions); session layer protocol sets up the connection to the other application logically and controls the dialog back and forth; session layer protocols allow applications to keep track of the dialog
IP protocol
connectionless; deals with addressing and routing of packets; works at the network layer (Layer 3); adds source and destination addresses to a packet as it goes through its data encapsulation process; IP can also make routing decisions based on the destination address
DHCP lease process
DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK
DHCPDISCOVER message
used to request an IP address lease from a DHCP server
DHCPOFFER message
a response to a discover message and sent by one or numerous DHCP servers
DHCPREQUEST message
client sends this message to the initial DHCP server which responded to its request
DHCPACK message
sent by the DHCP server to the DHCP client and is the process whereby the DHCP server assigns the IP address lease to the DHCP client
effective method to shield networks from unauthenticated DHCP clients is use of … on network switches
DHCP snooping
