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
Network Devices
Router
Gateway
Router - layer 3, routing table directs traffic
Gateway - any devices that performs a translation or acts as a control point for entry/exit
Firewalls
Packet filtering Stateful Circuit Level Proxy Application Level Proxy Dynamic Packet Filtering Kernel Proxy
Packet filtering
Stateful
Circuit Level Proxy - proxy server. rules controls traffic
Application Level Proxy - operates at higher level of OSI model than circuit proxy.
Dynamic Packet Filtering - ability to open certain ports dynamical based on the connection iniated from inside network
Kernel Proxy - firewall that operates at kernel level
Firewall Architectures
Bastion Host
Dual Homed
Three Legged
Screened Subnet
Bastion Host - unprotected, has to be locked down
Dual Homed - 2 NICS, one on internet, one to LAN
Three Legged - 3 NICs, one on internet, one to DMZ, one to LAN
Screened Subnet - 2 firewalls, area between them is the screened subnet
Cloud Computing
IAAS
PAAS
SAAS
IAAS - Infrastructure, vendor provides hardware
PAAS - vendor provides HW and SW
SAAS - vendor provides HW, SW, application
Network Types
LAN Intranet Extranet MAN WAN
LAN
Intranet - network within the LAN to host website
Extranet - network with resources accessible from outside world (partners, vendors)
MAN - network around a city, could be wired, wireless
WAN - wide area network
WAN Technologies
US
T Carriers. T1, T3
Europe
E Carriers. E1, E3
T1 - 24 channels, 1.544 Mbps
T3 - 672 channels, 44.736 Mbps (28 T1’s)
E1 - 2.048 Mbps
E3 - 8.
WAN Technologies
US
T Carriers. T1, T3
Europe
E Carriers. E1, E3
T1 - 24 channels, 1.544 Mbps
T3 - 672 channels, 44.736 Mbps (28 T1’s)
E1 - 2.048 Mbps
E3 - 34 Mbps
CSU / DSU
Channel Service Unit / Data Service Unit
Data Communications Equipment (DCE)
Data Terminal Equipment
CSU/DSU
Connects LAN to WAN. Translates information from LAN format to WAN compatible
DCE - provides interface to router
DTE - router
Network Connections
VOIP
create separate VLAN for IP phones
deploy VOIP aware firewall at perimeter
secure network layer with IPSec
Remote Access Technologies
Dialup
ISDN
Cable
DSL
ISDN - Basic Rate (BRI)
3 channels, total 144 Kbps
ISDN - Primary Rate (PRI)
23 channels for 1.544 Mbps
DSL
Symmetric DLS
Wireless Technologies
Frequency Hopping Spread Spectrum
Direct Sequence Spread Spectrum
Orthogonal Frequency Division Multiplexing
FHSS - bluetooth
DSSS - 802.11
OFDM - 802.11
ICMP Attacks
Ping of death Smurf Fraggle ICMP redirect Ping scanning
Ping of death - so many pings that target can’t do anything else
Smurf - amplified ping of death
Fraggle - like smurf but UDP
ICMP redirect - attacker changes route
Ping scanning - network scan
