Telecommunications and Network Security Flashcards
OSI Model
breaks communication process into layers
provides common framework for hardware and software developers
Layer 7, Application Layer
receives raw data from application in use and provides services to it
HTTP
DNS Queries
FTP
SMTP
Layer 6, Presentation Layer
manner in which data from application layer is presented to the destination application layer
MIME
XDR
Layer 5, Session Layer
adds information to packet that makes communication session possible between service or application on the source device with the same on the destination device
application or service in use is communicated with a port number
Layer 4, Transport
establishes session between 2 physical systems
either connection-oriented (TCP) or connectionless (UDP)
UDP header is much smaller, fewer features than TCP.
UDP is low overhead, TCP is high overhead
the PDU here is called a segment
Layer 3, Network
information needed route the packet is added here as a source and destination logical address (IP address)
PDU here is called a packet
examp protocols IP ICMP IGMP ARP
Layer 2, Data Link
determines physical address for destination
Media Access Control (MAC)
PDU here is called a frame
Adds a trailer at the end of the frame, containing data to verify none of the data inside has been altered en route
Layer 1, Physical
turns information into bits and sends it on medium
radio waves
electrical signals
light patterns
IP4 vs IP6 headers
IP4 is smaller but more complicated
TCP/IP Model
Has 4 layers
Application (OSI layer 5-7)
Transport (OSI layer 4 - same)
Internet (OSI layer 3)
Link (OSI layer 1-2)
Protocols and Ports to know
telnet SMTP SNMP FTP POP3 DNS DHCP LDAP
telnet, TCP, UDP 23 SMTP UDP, 25 SNMP, TCP, UDP 161, 162 FTP TCP, UDP, 20,21 POP3 TCP, UDP, 110 DNS, TCP, UDP 53 DHCP, UDP 67, 68 LDAP TCP, UDP 389
Network Transmissions
Asynchronous
Synchronous
Asynchronous - sender and receiver stay in synch with each other by sender inserting stop and start bits around the data
Synchronous - clock is used to synchronize the sender and receiver
Broadband
vs
Baseband
broadband - connection divided into frequencies. Each device or stream gets a different channel (frequency)
baseband - time slots assigned to devices or streams
Cabling
Coaxial
center core (solid or braided)
insulator, metallic shield, plastic jacket
Cabling
Twisted Pair
conductor, insulator, cable jacket
4 pairs of cable, each twisted around the other to prevent crosstalk
Cabling
Fiber Optic
core, cladding, outside jacket
Collision Domains
any part of network where devices’ packets can collide
a switch provides unique collision domains for each port
every device on a hub is in same collision domain
Contention Methods
CSMA/CD
CSMA/CA
Token Passing
Polling
CSMA/CD (wired ethernet)
(carrier sense multiple access collision detection). if a collision, message has everyone stop sending, then restart
CSMA/CA (collision avoidance) for wireless
devices tell each other when they’re getting ready to send
Token Passing (token ring) devices can't send until they receive an empty token
Polling
Network Protocols and Services
ARP
translates MAC to IP address
- send ARP request
- receive ARP reply
- adds to ARP cache
Network Protocols and Services
DHCP
- client sends DHCP Discover packet
- server sends DHCP Offer packet
- client sends DHCP Request
- server sends DHCP Pack
Routing Protocols
Standards RIP IS-IS OSPF BGP VRRP
Proprietary (Cisco)
IGRP, EIGRP
Network devices
Patch Panel
Multiplexer
Patch Panel - termination point for cables
Multiplexer - combines several input signals into one output signal
Network Devices
Hub
operates at layer 1
no intelligence
Network Devices
Hub
Switch
Hub
operates at layer 1
no intelligence
Switch
intelligence. Has MAC address table
