IS 404 Midterm- Data Communications
What is an IPS
Intrusion Protection System Protects from security risks and they protect availability of a network
What is a IDS
Intrusion detection system A device or software application that monitors a network or systems for malicious activity or policy violations
War driving
The act of searching for Wi-Fi networks by a person in a moving vehicle, using a portable computer, smartphone or personal digital assistant
What is CSMA/CA?
The client station listens for other users of the wireless network. If the channel is quiet(no data transmission), the client station can transmit. If the channel is busy, the station(s) must wait until transmission stops. Each client uses a unique random back-off time
Hybrid routing protocol
Uses characteristics of both distance-vector and link-state protocols Sends traditional distance-vector updates including cost of reaching remote networks(distance-vector) Sends specific update only when topology changes occur(link-state)
What does UDP stand for?
User Datagram Protocol
What is the difference between a host and a node?
A host is a computer on the network A node is any device that can communicate on the network
What is UDP?
A protocol provided on the internet protocol suite that does not provide guaranteed packet delivery.
What is TCP?
A protocol used by the Internet Protocol Suite that provides reliable, ordered, and error-checked delivery of a stream of octets between applications running on hots communicating by an IP network
What is Electromagnetic interference?
one electromagnetic field interferes with another, resulting in the distortion of both fields only a problem with copper cabling
Is 127.0.0.0/8 a public or private address?
private
On what layer of the OSI model is NIC cards?
1
How do the OSI and DOD(TCP/IP) Models relate?
1-2 of the OSI to 1 of TCP/IP 3 to 2 4 to 3 7-4 of the OSI to 4 of TCP/IP
What are the layers of the DOD Model?
1. Link Layer 2. Internet Layer 3. Transport Layer 4. Application Layer
What level of the OSI model are IP headers on?
3
What OSI layer can you find the MAC Address on?
2
What level of the OSI model are Frame headers on?
2
How many layers does the DOD Model have?
4
What is the format of a MAC address?
6 byte address or 48 bits often displayed as 6 pairs of Hexadecimal digits(12) The first 6(3 bytes) numbers identify the manufacturer The last 6(3 bytes) numbers identify the NIC
How many Layers does the OSI Model have?
7
How and when are MAC addresses used?
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What is a broadcast domain?
A broadcast domain is a domain in which a broadcast is forwarded. A broadcast domain contains all devices that can reach each other at the data link layer (OSI layer 2) by using broadcast.
Fiber
A cable containing one or more optical fibers that are used to carry light. The fiber elements are typically coated with plastic glass layers and contained in a protective tube.
What is a collision domain?
A collision domain is, as the name implies, a part of a network where packet collisions can occur. The packets collide and both devices must send the packets again, which reduces network efficiency.
NIC cards-
A computer hardware component that connects the computer to a computer network
OSI Model
A conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology.
What is the DOD Model? (TCP/IP)
A conceptual model that provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed and received.
What are Switches ?
A device that filters and forwards packets between LAN segments.
Repeaters-
A device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction (like a wall). Repeaters forward everything including collisions. Ports on a repeater do not have MAC addresses It will still send collisions It will clean the signal of noise
Routers
A device used to send information between networks. Breaks Broadcast domains
What is packet switching?
A digital networking communications method that groups all transmitted data into suitably sized blocks, called packets, which are transmitted via a medium that may be shared by multiple simultaneous communication sessions.
What is CSMA/CD?
A media access control(MAC) most notably used in Ethernet technology. It uses a carrier sensing scheme in which transmitting station detects collisions by sensing transmissions from other stations while transmitting a frame. When this collision is detected, the station stops transmitting the frame, transmits a jam signal, and waits for a random time interval before trying to resend the frame.
What is ARP?
A protocol used by the Internet Protocol(IP) to map IP network addresses to the hardware addresses used by a data link protocol
Distance Vector Protocols
A routing protocol that uses distance(hops) and direction to determine the best path to a remote network. Shortest paths are updated
What does Telnetting you to do?
A telnet program allows a user at a terminal or PC to log in to a remote computer (or switch) and run a program and execute other Unix commands.
What is Telnetting?
A terminal emulation protocol used on the internet and TCP/IP-based networks.
Token Ring
A token is passed around to network devices it's in a ring shape too Pros: It is a Deterministic network All devices are guaranteed access to the network at fixed intervals Cons: If an error changes the token pattern...the system breaks Relies every station to pass the message along, this can cause a problem if one device breaks Adding or removing a station causes downtime
What is circuit switching?
A type of communication in which a dedicated channel(or circuit) is established for the duration of a transmission.
MAC Address
A unique identifier assigned to network interfaces for communications at the data link layer of a network segment. MAC addresses are assigned by the manufacturer of the device.
Mesh
All host are connected to each other Pros: Redundancy Cons: Most expensive Complex
Bus / Ethernet
All hosts are connected to the same cable Pros: Multiple devices can communicate at the same time Cons: Everything can see the flow of information Bandwidth gets eaten like a boss
Amplifiers
Amplifies signal and noise An electronic device that increases the voltage, current, or power of a signal. Makes it so you need less repeaters
Physical Layer Data Types
Bits
What does CSMA/CA stand for?
Carrier Sense Multiple Access with Collision Avoidance-(wireless)
What does CSMA/CD stand for?
Carrier Sense Multiple Access with Collision Detection-(wired)
UTP
Cat 1 -Telephone communications Cat 2 -4Mbps Speeds Cat 3 -10Base-T networks 10Mbps Cat 4-Used in token rings for 16Mbps Cat 5 - 100Mbps speeds Cat 5e -1000Mbps speeds Cat 6- Fastest
Coaxial
Central copper conductor surrounded by flexible insulation Woven copper braid or metallic foil acts to shield inner conductor
What are the private Ip address spaces?
Class A: 10.0.0.0(it just needs the 10) Class B; 172.16.0.0 - 172.31.0.0 Class C: 192.168.0.0 - 192.168.255.0
Hubs
Collisions are a problem These are half-duplex devices They can't send information on a port at the same time they are receiving it and vise versa - like a walkie talkie A device that makes a common connection point for devices in a network. Hubs are "commonly" used to connect segments of a LAN. When a packet of data arrives at one port, it is copied and broadcasted to the other ports so all segments of the LAN can see all packets
What is circuit switching ideally used for?
Communications that require data to be transmitted in real-time For example telephone systems.
How do Link State Protocols differ from Distance Vector protocols?
Coverage is faster Less bandwidth usage More CPU is used by the routers They support classless routing They send updates via multicast addresses Routing tables are only changed when new routes are added to the network Hard to configure
Presentation Layer Data Types
Data
Session Layer Data Types
Data
Data Link Layer
Data packets are encoded and decoded into bits It handles errors in the physical layer, flow control, and frame synchronization
Channel
Different frequencies that a signal can be sent on within a given band
What are some guidelines for IP addressing ( formatting constraints)?
Host and network addresses cannot have all bits set to 0 or 1 The network address can not be 127 All hosts on a given network must have unique addresses
How do Distance Vector Protocols compare to link state protocols?
Distance Vector Protocols are easier to configure than link-state protocols and require little management They are more susceptible to routing loops The information travels between routers in a loop Convergence is slower with Distance Vector Protocols than Link State protocols Distance vector protocols eat more bandwidth
How does the Distance Vector protocol work?
Distance vector protocols send complete routing tables to each neighboring router. A neighbor is a directly connected router that runs the same protocol as the router sending the information. Routing tables are sent out a fixed intervals
Interference (causes)
EMI Bending a fiber optic cable...this will ruin the cable Anything on the same frequency when you are talking about wi-fi Also anything between your device and the router...that includes humidity
Examples of UDP
FaceTime, Skype, voice and video traffic
Data Link Layer Data Types
Frames
Are Switches full-duplex or half duplex devices?
Full duplex AKA they can send information on a port at the same time they receive it - Like a telephone
Application Layer Data Types
HTTP requests for web browsing FTP for file transfers Simple Mail Transfer Protocol(SMTP) for email transmission
What are the parts of the ARP header?
Hardware type (HTYPE) Protocol Type(PTYPE) Sender Hardware address Sender Protocol Address Target Hardware address(THA) Target protocol address(TPA)
Why are Channels used?
Having different channels allows more information to be sent without the risk of interference between multiple signals
What is the IP address 127.0.0.0/8 used for?
It is the loopback address and is used for routing to a machine locate on the sending machine (basically it is used to help the computer talks to itself or rather programs it is running)
What layer are ARP Headers found on?
Layer 2 of OSI model
What does it mean if the fiber is Multi-mode?
Light bounces off edges at different angles so that multiple signals can travel down the same core at the same time
Session Layer
Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes
What does MAC Address stand for?
Media Access Control Address
What are the Data Link Layers two sublayers and what do they do?
Media Access Control(MAC) Layer This layer controls how a computer on the network gains access to the data and permissions to transmit it Logical Link Control(LLC) Layer- This layer controls frame synchronization, flow control, and error checking.
STP
More heavily protected from electromagnetic interference than UTP All 4 pairs are wrapped in an overall metallic braid or foil The whole is also wrapped in a shield
What is the Link state protocol we learn in this class?
OSPF
What are the OSI Layers in order?
People Don't Need To See People Age 1. Physical Layer 2. Data Link Layer 3. Network Layer 4. Transport Layer 5. Session Layer 6. Presentation Layer 7. Application Layer
What does it mean if the fiber is single mode?
One light travels down a smaller central core
Network Layer Data Types
Packets/Datagram
Twisted pair - UTP, STP
Pairs are twisted to provide protection against cross talk (bits jumping between wires) (EMI)
Examples of TCP
Peer-to-peer, media streaming, Youtube, Spotify, Apple Music
Network Layer
Provides switching and routing technologies, creating logical paths for transmitting data from node to node(device to device) Routing and forwarding are functions of this layer as well as addressing, internetworking, error handling, congestion control, and packet sequencing.
What are two example Distance Vector Protocols?
RIP and EIGRP
What is Attenuation affected by?
Range Interference Medium characteristics
Transport Layer Data Types
Segment(TCP)/DataGram(UDP)
Elements of data communication systems
Sender, Receiver, Transmission Medium, Protocols
What are the parts for the UDP header?
Source Port Destination port Length Checksum
What are the parts of the TCP header?
Source Port Destination port Sequence number Acknowledgment number(ACK) Data offset ACK (flag) SYN (flag) FIN(flag)
What are the Network topologies?
Star Mesh Bus / Ethernet Token Ring
How do switches know where to send packets?
Switches keep a table of MAC addresses for every device connected to them. They use this information to forward packets
What is Bandwidth?
The amount of data transmitted in a given time period. Typically expressed in bits per second (bps) and megabits per second(Mbps)
What is Attenuation?
The gradual loss in intensity of any kind of flux through a medium. Attenuation affect the propagation of waves and signals in electrical circuits, in optical fibers, and in air (radio waves)
Star
The name describes how it is designed. Either a switch or a hub can be at the center of the star
What is Subnetting?
The practice of dividing a network into two or more networks or subnets.
What is a Collision on a network?
The result of two devices on the same Ethernet network attempting to transmit data at the same time Any computer on the same network segment can cause a collision
Frame(layer 2)
The unit of transmission in a link layer protocol, and consists of a link layer header followed by a packet
What layer of the OSI model do Switches operate on?
These devices operate at the data link layer of the OSI Model and can support and packet protocol.
Link State Protocols
They advertise changes in the network topology( new routers and their neighboring links) Each update has a sequence number that increases with each update Nodes identify themselves when broadcasting Nodes only have to identify nodes in their area
Application Layer
This layer interacts with application programs that incorporate a communication component such as your Internet browser and email. It is responsibly for logging the message in, interpreting the request, and determining what information is needed to support the request.
Transport Layer
This layer is concerned with message integrity between source and destination. It segments/and reassembles the packets and handles flow control
What does UDP do?
This protocol is used primarily for establishing low-latency and loses tolerating connections between applications on the internet (ex. video games, DNS, SMTP).
Presentation Layer
Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
What are the 3 Types of transmission media?
Twisted pair - UTP, STP Coaxial Fiber
Describe the difference between Unicast, Broadcast and Multicast.
Unicast- Send it to one host Multicast- send it to whoever is listening Broadcast- Send it to ALL OF THE HOSTS(all bits are set to 1)
How do Switches differ from a hub?
Unlike hubs, switches are smart enough to know which packets of data need to be delivered to what device on the LAN.
What are some of the fields inside of the IPv4 header?
Version Flags Protocol Time to Live Source/Destination Ip address Total Length Header checksum Identification
Do switches handle collisions?
Yes
What exactly is 802.11?
a standard for wireless LANs. It defines the physical layer (PHY), the medium access control (MAC) layer, and the MAC management protocols and services
How is Subnetting done?
designating some high-order bits from the host part of an IP address and grouping them with the network mask to form the subnet mask
Amendments (e.g., a, b, g, n, ac)
see picture on google drive
Physical Layer
transmission and reception of unstructured raw data in a physical medium
