IST 220 - Exam 3 Review
ZigBee
- 802.15.4 (low powered bluetooth)
Common characteristics of different 802.11 standards
- All use the same medium access protocol (CSMA/CA) - All use the same frame structure for their link-layer frames - Have the ability to reduce their transmission rate in order to reach out over greater distances - All backwards compatible, meaning that a mobile capable of 802.11f may still interact with with a newer 802.11ac base station
Classes of medium access protocols
- Channel partitioning - Random access - Taking turns
Wireless/Wired Differences
- Decreasing signal strength - Interference from other sources - Multipath propagation
Single-hop, infrastructure-based
- Have a base station connected to a larger wired network - All communication is between this base station and a wireless host over a single wireless hop - Ex. 802.11 networks and 4G LTE data networks - Vast majority of our daily interactions are with this type of wireless network
Multi-hop, infrastructure-based
- Have a base station connected to a larger wired network - Some wireless nodes may have to relay their communication through other wireless nodes in order to communicate via the case station - Ex. some wireless sensor networks and "wireless mesh networks"
Disadvantages of increasing transmission power
- Having to expend more energy - Increase in interference with the transmissions of another signal
Multi-hop, infrastructure-less
- No base station connected to a wired network - Nodes may have to relay messages among several other nodes in order to reach a destination - Nodes may be mobile, with connectivity changing among nodes - a class of networks known as mobile ad hoc networks (MANETs) - Network is a vehicular ad hoc network (VANETs) if the mobile nodes are vehicles - Development of protocols for such networks is challenging and is the subject of much ongoing research
Single-hop, infrastructure-less
- No base station connected to a wireless network - One of the nodes may coordinate the transmissions of other nodes - Ex. bluetooth and 802.11 networks in ad hoc mode
Multipath Propagation
- Occurs when portions of the electromagnetic wave reflect off objects and the ground, taking paths of different lengths between a sender and receiver - Could result in the received signal at the receiver to be blurred - Moving objects between the sender and receiver can cause multipath propagation to change over time
Major differences of different 802.11 standards at the physical layer
- Operate in 2 frequency ranges: 2.4 - 2.485 GHz and 5.1 - 5.8 GHz - Most recent standards are 802.11n (2.4 GHz) and 802.11ac (5 GHz) - Some base stations use multiple input multiple-output (MIMO) antennas; 2 or more antennas on the sending side and 2 or more on the receiving side that are transmitting/receiving different signals
Types of Firewalls
- Stateless packet filters (traditional) - Stateful packet filters - Application gateways
Carrier Sense Multiple Access w/ Collision Avoidance (CDMA/CA)
- WiFi's collision detection system - Each station senses the channel before transmitting, and refrains from transmitting if the channel is found busy
Wireless/Wired Equivalents
- Wireless 802.11 ~ wired ethernet - Wireless interface ~ ethernet interface - Access point ~ ethernet switch - Changes only occur as the link layer during a switch from ethernet to wireless or vice versa
Base Station
- a key part of the wireless network infrastructure - responsible for coordinating the transmission of multiple wireless hosts which it is associated with
Ad Hoc Network
- a network with no central control and with no connections to the "outside world" - formed when people with laptops get together and want to exchange data in the absence of a centralized AP
Secure Hash Algorithm (SHA-1)
- a secure hash algorithm that creates 160-bit hash values - used in DSS
Code Division Multiple Access (CDMA)
- a shared-medium access protocol that is often used in wireless networks - belongs to a family of channel partitioning protocols - prevalent in wireless LAN and cellular technologies
MD5 Hash
- a widely used hash algorithm that produces 128-bit hash values - has vulnerabilities - used to verify data for integrity
IPsec Services
- data integrity - origin authentication - replay attack prevention confidentiality
Source Description Packets
- e-mail address of sender, sender's name, SSRC of associated RTP stream - provide mapping between the SSRC and the user/host name
SIP Services
- provides mechanisms for call setup - determines current IP address of callee - call management
RTCP Packet Types
- receiver report packets - sender report packets - source description packets
Basic Service Set (BSS)
- the fundamental building block of the 802.11 architecture - contains one or more wireless stations and a central base station, known as an *access point (AP)*
Service Set Identifier (SSID)
- the unique name of a wireless network that differentiates it from other wireless networks that are also in range of a wireless client - generated by the network administrator when it installs an AP that's assigned to the access point
Security Association Database (SAD)
- where an IPsec entity stores the state information for all its SAs - a data structure in the entity's OS kernal - where the endpoint holds SA state
WEP Authenication
1. Authentication request --> 2. Nonce (128-bytes) <-- 3. Nonce encrypted shared keys --> 4. Success if decrypted value equals nonce <--
3 Goals of Network Security
1. Confidentiality 2. Integrity 3. Availability
802.11i Phases of Operation
1. Discovery of security capabilities 2. STA and AS mutually authenticate, together generate Master Key (MK) 3. STA derives Pairwise Master Key (PMK); AS derives same PMK, sends to AP 4. STA, AP use PMK to derive Temporal Key (TK) used for message encryption, integrity
SSL
1. Handshake - sender and receiver use their certificates, private keys to authenticate each other and exchange shared secret 2. Key Derivation - Sender and receiver use shared secret to derive set of keys 3. Data Transfer - Data to be transferred is broken up into records 4. Connection Closure - Special messages to securely close connection (vulnerable to the possibility of attackers replaying messages)
Skype Client Operation
1. Joins Skype network by contacting SN using TCP 2. Logs-in to centralized Skype login server 3. Obtains IP address for callee from SN, SN overlay 4. Initiate call directly to callee
Firewall Goals
1. Prevent denial of service attacks 2. Prevent illegal modification/access of internal data 3. Allow only authorized access to inside network
Three classifications for streaming video systems
1. UDP Streaming 2. HTTP Streaming 3. Adaptive Streaming
802.11n
2.4-5 GHz/5 GHz; up to 200 (or 450) Mbps
802.11b
2.4-5 GHz; up to 11 Mbps
802.11g
2.4-5 GHz; up to 54 Mbps
Assured Forwarding (AF)
4 classes of traffic
Audio via CD
44100 samples per second
802.11ac
5 GHz; up to 1300 Mbps
802.11a
5-6 GHz; up to 54 Mbps
Audio via telephone
8000 samples per second
overlapping channels
802.11 LANs define 11 partially ____________ within the frequency range of 2.4 GHz to 2.4835 GHz
Bluetooth
802.15.1 ~ 2.4-2.5 GHz, up to 721 kbps
Emergency Services
911
Security Parameter Index (SPI)
A 32-bit identifier for the SA
Session Initiation Protocol (SIP)
A VoIP signaling protocol used to set up, maintain, and tear down VoIP phone calls.
H.323
A VoIP standard that handles the initiation, setup, and delivery of VoIP sessions.
Advanced Encryption Standard (AES)
A block cipher created in the late 1990s that uses a 128-bit block size and a 128-, 192-, or 256-bit key size; practically uncrackable
Integrity Check Value (ICV)
A checksum based on the contents of the text, used in WEP encryption.
Block Cipher
A cipher that manipulates an entire block of plaintext at one time
Cyclic Redundancy Check (CRC)
A code added to data which is used to detect errors occurring during transmission, storage, or retrieval
Digital Signature
A code digitally signed by a company or person; verifiable and non-forgeable
Real-time Transport Control Protocol (RTCP)
A companion to RTP, defined in RFC 3550 by the IETF, RTCP provides feedback on the quality of a call or video conference to its participants.
Security Policy Database (SPD)
A data structure that indicates what types of datagrams are to be IPsec processed
Stateful Packet Filtering
A firewall technology that creates and maintains a table in memory that lists all established connections between the organization's computers and the Internet
Application Gateway
A firewall technology that filters packets based on application data as well as on IP/TCP/UDP fields
Stateless Packet Filtering
A firewall technology that looks at the incoming packet and permits or denies it based strictly on the rule base.
Hash-based Message Authentication Code (HMAC)
A fixed length string of bits similar to other hashing algorithms such as MD5 and SHA-1, but it also uses a secret key to add some randomness to the result; most popular standard for MACs today
Extensible Authentication Protocol (EAP)
A framework for transporting authentication protocols that defines the format of the messages. (Mobilr)
Authentication (Protocol)
A method for confirming users' identities
Pretty Good Privacy (PGP)
A method of encrypting and decrypting e-mail messages. It can also be used to encrypt a digital signature.
Substitution Cipher
A method of encryption and decryption in which each letter in the alphabet is replaced by another
Streaming
A method of sending audio and video files over the Internet in such a way that the user can view the file while it is being transferred; stored at server
Piconet
A network of Bluetooth devices
Transport Layer Security (TLS)
A protocol based on SSL 3.0 that provides authentication and encryption, used by most servers for secure exchanges over the Internet.
SSL Handshake
A protocol for the beginning of an interaction. 1. Bob establishes a TCP connection with Alice (TCP SYN, TCP/SYNACK, TCP ACK) 2. Bob verifies Alice is really Alice (SSL hello, certificate) 3. Bob sends Alice a master secret key, which will be used by both to generate all the symmetric keys they need for the SSL session (EMS = Kv(A)^(+) (Master Secret, or MS)
Internet Key Exchange (IKE)
A protocol used to set up an IPsec session.
Beacon Frames
A series of frames used in WiFi (802.11) to establish the presence of a wireless network device
IP Security Protocol (IPsec)
A set of open, non-proprietary standards that you can use to secure data as it travels across the network or the internet through data authentication and encryption.
Quality of Service (QoS)
A set of parameters that controls the level of quality provided to different types of network traffic
Request to Send (RTS)
A signal used in wireless networks indicating that a computer has data ready to send on the network
Message Authentication Code (MAC)
A small block of data that is generated using a secret key and then appended to the message
Secure Socket Layer (SSL)
A standard security technology for establishing and encrypting links between a web server and a browser, ensuring that all data passed between them remain private
Ciphertext
A string of text that has been converted to a secure form using encryption
Data Encryption Standard (DES)
A symmetric block cipher that uses a 56-bit key and encrypts data in 64-bit blocks
Prefetching
A technique in which data blocks needed in the future are brought into the cache early by the use of special instructions that specify the address of the block.
Intrusion Prevention System (IPS)
A technology that monitors activity like an IDS but will automatically take proactive preventative action if it detects unacceptable activity.
IP Spoofing
A type of spoofing whereby an intruder uses another site's IP address as if it were that other site
Frequency Hopping Spread Spectrum (FHSS)
A type of wireless technology that spreads its signal over rapidly changing frequencies
Vehicular Ad Hoc Networks (VANETs)
Ad hoc networks with vehicles
Mobile Ad Hoc Networks (MANETs)
Also known as wireless ad hoc network or ad hoc wireless network, is a continuously self-configuring, infrastructure-less network of mobile devices connected wirelessly.
Wired Equivalent Privacy (WEP)
An IEEE 802.11 security protocol designed to ensure that only authorized parties can view transmitted wireless information. WEP has significant vulnerabilities and is not considered secure.
Cryptographic Hash Function
An algorithm that is run on a file, producing a value called a checksum
Real-Time Streaming Protocol (RTSP)
An application layer protocol that servers and the Internet use to deliver streaming audio and video data to a user's browser.
Man-in-the-middle (MITM) Attacks (or Session Hijacking)
An attack that is placed by an active attacker who listens to the communication between two communicators and changes the contents of this communication. While performing this attack, the attacker pretends to be one of the parties to the other party.
Rivest Shamir Adleman (RSA)
An improved public-key cryptography algorithm that enables secure digital signatures
WiFi Jungle
Any physical location where a wireless station receives a sufficiently strong signal from two or more APs
IPsec Protocols
Authentication Header (AH) Encapsulation Security Payload (ESP)
400 ms
Bi-directional voice/video needs to have a delay no more than _______ milliseconds.
MPEG-1
CD-ROM, 1.5 Mbps
Link and network
Challenges posed by networking wireless and mobile devices usually occur at what layers?
Virtual Private Network (VPN)
Companies can establish direct private network links among themselves or create private, secure Internet access, in effect a "private tunnel" within the Internet
Chosen-plaintext Attack (CPA)
Cryptanalysis attack where the attacker can choose arbitrary plaintexts to be encrypted and obtain the corresponding ciphertexts
Known-plaintext Attack (KPA)
Cryptanalysis attack where the attacker is assumed to have access to sets of corresponding plaintext and ciphertext
MPEG-2
DVD, 3-6 Mbps
Public Key Certification
Data that associates a public key with a specific owner, signed by a CA that attests to its correctness
Interconnection Devices
Devices such as routers, switches and hubs
Carrier Sense Multiple Access w/ Collision Detection (CSMA/CD)
Ethernet's collision detection system
802.11 frame
Four different addresses... 1. MAC address of wireless host or AP to receive this frame 2. MAC address of wireless host or AP transmitting this frame 3. MAC address of router interface to which AP is attached 4. Used only if in ad hoc mode
Receiver Report Packets
Fraction of packets lost, last sequence number, average inter-arrival jitter
Masters
Grants requests (from slaves)
wireless; wired
Hidden terminal problems make multiple access in a __________ network considerably more complex than in a _________ network
Infrastructure Mode
Hosts associated with a base station and all traditional services provided by network to which host is connected are referred to as operate in...
Delay Loss
IP datagram arrives too late for playout at receiver
Network Loss
IP datagram lost due to network congestion
Synchronization Source Identifier (SSRC)
Identifies the source of the RTP stream; each stream in RTP session has distinct SSRC (32 bits)
Distributed Inter-frame Space (DIFS)
If the sender senses the channel is idle it transmits after a short period of time
Per-hop Behavior (PHB)
In differentiated service, this is a class of descriptors of available service levels, or a way of describing protocols and priorities applied to a packet on traversing a router "hop."
Transmission Power
Increasing the _____________ increases SNR, which also decreases the probability that a frame is received in error
MPEG-4
Internet, < 1 Mbps
Firewall
Isolates organization's internal network from the Internet, allowing some packets to pass, blocking others
Cryptographic Keys
Kv(c) = encryption key for data sent from client to server Mv(c) = MAC key for data sent from client to server Kv(s) = encryption key for data sent from server to client Mv(s) = MAC key for data sent from client to server
Policing Mechanisms
Limits traffic as to not exceed declared parameters; three common-used criteria... 1. Average rate - how many packets can be sent per unit time 2. Peak rate 3. Burst Size - max number of packets sent consecutively
Plain Text/Clear Text
Message data before it is encrypted
Skype Network
P2P Components... 1. Clients 2. Super nodes 3. Overlay network 4. Login server
Hidden Terminal Problem
Physical obstructions in the environment may prevent two stations from hearing each other's transmissions, even though their transmissions are interfering with each other at a 3rd location resulting in undetectable collisions
Real-Time Transport Protocol (RTP)
Protocol that defines the type of packets used on the Internet to move voice or data from a server to clients. The vast majority of VoIP solutions available today use RTP.
Real-time Transport Protocol (RTP)
Protocol that defines the type of packets used on the Internet to move voice or data from a server to clients. The vast majority of VoIP solutions available today use RTP.
Personal Area Network (PAN)
Provide communication over a short distance that is intended for use with devices that are owned and operated by a single user
802.11 Advanced Capabilities
Rate adaptation and power management
Spatial Redundancy
Redundancies that occur within a single frame of video whenever the value of a pixel is repeated across a series of adjacent pixels.
Temporal Redundancy
Redundancy that reflects repetition from one image to the next
Timestamp Field
Reflects the sampling instant of the first byte in the RTP data packet (32 bits)
Slaves
Request permission to send (to masters)
Sender Report Packets
SSRC of RTP stream current time, number of packets sent, number of bytes sent
ap 5.0
Same as ap 4.0, but uses public key cryptography (vulnerable to MITM attacks)
CSMA/CA
Sender 1. If sense channel idle for DIFS, then... transmit entire frame (no CD) 2. If sense channel busy, then... start random backoff time timer counts down while channel idle transmit when timer expires ...if no ACK, increase random backoff interval (repeat 2) Receiver If frame received OK, then... return ACK after SIFS (ACK needed due to hidden terminal problem)
ap 4.0
Sender sends a message claiming to be someone; Receiver sends a none (once in a lifetime protocol); Sender encrypts key and sends it to the destination (used to make sure the sender is live and online); Receiver decrypts the message and if the nonce's equal each other then the sender is authenticated! (vulnerable to MITM attacks)
ap 3.0
Sending a message saying who you are including a secret password. The attacker can record the packet and play it back later.
ap 3.1
Sending a message saying who you are including an encrypted secret password. The attacker can record the packet and play it back later.
ap 2.0
Sending a message saying who you are, including the IP address. The IP can be spoofed and the message can be sent from someone else
ap 1.0
Sending a message saying who you are, someone can easily claim they are someone else
UDP; RTP
The ______ transport layer protocol and ______ application layer protocol are used for real-time multimedia.
Interactivity
The ability of the user to interact with an application (play, pause, rewind, etc.)
Message Integrity
The ability to be certain that the message being sent arrives at the proper destination without being copied or changed
Fading
The fading of a signal's strength due to undetectable collisions at the receiver as it propagates through the wireless medium
Clear to Send (CTS)
The hardware signal that is sent from a receiver to a transmitter to indicate that the transmitter can begin sending
BER
The higher the SNR, the lower the...
Internet access
The host must associate with at least one AP to gain _________
Network Infrastructure
The larger network with which a wireless host may wish to communicate
SNR
The lower the BER, the higher the...
Dynamic Adaptive Streaming over HTTP (DASH)
The multimedia protocol used to manage audio/video at different bit rates from a streaming media server (like YouTube) using TCP
Bit Error Rate (BER)
The probability that a transmitted bit is received in error at the receiver
Active Scanning
The process of broadcasting a probe request frame that will be received by all APS within the wireless device's range 1. Probe Request frame broadcast from H1 2. Probe Response frames sent from APs 3. Association Request frame sent: H1 to selected AP 4. Association Response frame sent from selected AP to H1
End-point Authentication
The process of one entity proving its identity to another entity over a network
Passive Scanning
The process of scanning channels and listening for beacon frames 1. Beacon frames sent from APs 2. Association Request frame sent: H1 to selected AP 3. Association Response frame sent from selected AP to H1
Chipping Rate
The rate at which the signal being multiplied by each bit in a CDMA protocol changes during the encoding process
Path Loss
The reduction in signal strength due to the increase in distance between the sender and the receiver
Short Inter-frame Spacing (SIFS)
The short period of time before the destination sends back an ACK
IEEE 802.11 wireless LAN (WiFi)
The standard class for wireless LANs
Security Association (SA)
This generates the encryption and authentication keys that are used by IPsec.
Authentication Header (AH)
This provides source authentication and data integrity, but does not provide confidentiality
Encapsulation Security Payload (ESP) Protocol
This provides source authentication, data integrity and confidentiality; more widely used than AH
Loss-tolerant
Transmissions that can tolerate occasional loss of data without compromising the user experience.
Delay-sensitive
Transmissions that will suffer significantly compromised user experiences if portions of the transmission are delayed, such as with voice and video transmissions.
Playback Attack
Trudy need only eavesdrop on Alice's communication, record the encrypted version of the password, and play back the encrypted version of the password to Bob to pretend that she is Alice.
Sequence Number Field
Used by the receiver to detect packet loss and to restore packet sequence (16 bits)
Encryption Key
Used to encrypt and decrypt data
Voice over IP (VoIP)
Uses IP technology to transmit telephone calls
HTTP Streaming
Uses TCP to stream audio and video
UDP Streaming
Uses the RTP protocol and RTSP servers
Public Key Encryption (PKE)
Uses two keys... 1. a public key everyone can have 2. a private key for only the recipient
Internet Telephony
Using the internet rather than the telephone network to exchange spoken conversations
Constant Bit Rate (CBR)
Video encoding at a fixed rate
Variable Bit Rate (VBR)
Video encoding rate changes as amount of spatial, temporal coding changes
Bit errors
What are more common in wireless links than in wired links? They require wireless link protocols to employ powerful CRC error detection codes and link-level reliable-data-transfer protocols that retransmit corrupted frames.
Client Buffering
When a client builds up a reserve of several seconds video that has buffered but not yet been played
Protocol
When hosts communicate over a shared medium, a _________ is needed so that the signals sent by multiple senders do not interfere at the receivers
Infrastructure Wireless LANs
Wireless LANs that deploy APs
Security Hole
a bug that permits unauthorized access
Intrusion Detection System (IDS)
a computer program that senses when another computer is attempting to scan or access a computer or network
Checksum
a data transmission control that uses a hash of a file to verify accuracy
Deep Packet Inspection
a process that examines the data in the body of a TCP packet to control traffic, rather than looking only at the information in the IP and TCP headers
Packet Filtering
a process that uses various fields in a packet's IP and TCP headers to decide what to do with the packet
WiFi Hotspot
a public location where users can find 802.11 wireless access
Signal-to-noise Ratio (SNR)
a relative measure of the strength of the received signal (or the information being transmitted) and this noise; measured in decibels (dB)
Demilitarized Zone (DMZ)
a separate network located outside the organization's internal information system that permits controlled access from the internet
Access Control List (ACL)
a set of IF-THEN rules used to determine what to do with arriving packets
Certification Authority (CA)
a trusted organization or company that validates identities and issues digital certificates used to create digital signatures and public-private key pairs
Session Key
a unique symmetric encryption key chosen for a single secure session
Conversational
affected by delay
5 GHz range
an unlicensed frequency band, where 802.11 LANs have a shorter transmission distance for a given power level and suffer more from multipath propagation
2.4 GHz range
an unlicensed frequency band, where 802.11 devices may compete for frequency spectrum with 2.4 GHz phones and microwave ovens
Value-added Services
call forwarding, screening, recording
Packet Scheduling
choose next queued packet to send on outgoing link
Client-side buffer and playout delay
compensate for delay jitter
Loss tolerance
depending on voice encoding, loss concealment, packet loss rates between 1% and 10% can be tolerated
Relays
devices that automatically turn switches in electric circuits on and off
Session Initialization
how does callee advertise IP address, port number, encoding algorithms
Network Dimensioning
how much bandwidth is "enough"
Token Bucket
limit input to specified burst size and average rate
Adaptive Playout Delay
low playout delay, low late loss rate
Estimated Network Traffic Demand
needed to determine how much bandwidth is "enough" (for that much traffic)
Delay Jitter
network-added delay
Continuous Playout Constraint
once client playout begins, playback must match original timing
Expedited Forwarding (EF)
packet departure rate of a class equals or exceeds specified rate
Statistical Analysis
performs such functions as information correlations, distributions, calculations, and variance analysis
Video Compression
reduces the size of video images while retaining the highest quality video with the minimum bit rate
End-to-end Delay
the accumulation of transmission, processing and queuing delays in routers; propagation delays in links; and end-systems processing delays
Certificate
the binding of the public key of the entity to the identity
Rate Adaptation
the capability to adaptively select the underlying physical-layer modulation technique to use based on current or recent channel characteristics
Power Management
the capability to minimize the amount of time that 802.11 nodes sense, transmit, and receive functions and other circuitry need to be "on"
Cipher-text Only Attack
the hacker gains copies of several messages encrypted in the same way (same algorithm). Statistical analysis can then be used to reveal eventually, repeating code, which can be used to decode messages later
If a host remains in the same subnet,...
the host's IP may remain the same; the switch will see the frame from the host and remember which port it came from therefore remembering which AP the host is associated with
Brute Force Attack
the password cracker tries every possible combination of characters
Handoff
the process of a mobile changing its point of attachment into the larger network when it moves beyond the range of one base station and into the range of another
symmetric-key cryptography (PSK)
the sender and receiver use the same key for encryption and decryption
