The Bits and Bytes of Computer Networking Flashcards
If a computer were to perform a full DNS lookup using TCP, how many packets would have to be sent between it and all name servers?
44
Using UDP, how many packets would need to be sent to perform a full DNS look up?
8
What Transport layer protocol does DNS normally use?
UDP (User Datagram Protocol)
A DNS TTL determines what?
How long a DNS entry is allowed to be cached in the Recursive Server
What is DNS Round Robin?
A method of load balancing where multiple IP addresses are assigned to a domain name. During DNS Resolution, all IPs are shared but the order rotates in each look up to spread out traffic.
In DNS Resolution, what is an A Record used for?
To point a certain domain name at a certain IPv4 IP Address
What is a AAAA - Quad A Record?
Used to point a domain name at a certain IPv6 IP Address during DNS Resolution
What is a CNAME Record?
Canonical Name Record
Used to redirect traffic from one domain to another (Eg: microsoft.com to www.microsoft.com). Setting up a CNAME means you only need to update the IP of one domain name if it changes.
What is an MX Record?
Mail Exchange Record
Used to deliver email to the correct server
What is an SRV Record?
Service Record
Used to define the location of various specific services.
(Like how MX is for email, SRV is for many service types)
What is a TXT Record?
Text Record
Used to provide the ability to associate text with a zone. This record allows domain administrators to insert any text content into DNS records. These records are used for various purposes. One example is ownership validation: To prove you own the domain, a provider may require you to add a TXT record with a particular value to your domain.
What are the 3 main parts of a domain name?
1) Subdomain - Or Host Name, eg: www.
2) Domain - The name portion, eg: google in google.com. Stored on the Authoritative Name Server.
3) TLDs (Top Level Domains) - the final portion of the domain name, eg: .com. Stored on TLD Name Servers.
How does UDP differ from TCP when transmitting data?
TCP requires constant connection and acknowledgement for every segment of a data packet to ensure nothing is lost
UDP just sends the data to it’s destination port. No string of acknowledgement means more available bandwidth. Good for streaming videos where a few missing frames won’t matter
Cat 5, Cat 5e, and Cat 6 cables are made with increasingly strict specifications to avoid _______.
Crosstalk
What does BGP stand for?
Border Gateway Protocol
What does Modulation do when transmitting data across cables?
Modulation is a way of varying the voltage of the charge moving across a cable in a constant ‘on’ state.
What does the Physical Layer consist of?
Devices and cables, means of transmitting bits across a computer network
What are the 2 main network protocols?
-TCP (Transmission Control Protocol)
-IP (Internet Protocol)
What does UDP stand for?
User Datagram Protocol
What is Crosstalk?
When an electrical pulse on one wire is accidentally detected on another wire
When a TCP Socket sends a FIN, but the corresponding ACK from the other end hasn’t been received yet, what will it’s state be?
FIN_WAIT
What does the TCP socket state SYN_SENT mean?
A synchronization request has been sent, but the connection hasn’t been established yet. (Client side only)
When a TCP Connection is ready to be closed, a four-way handshake occurs, in order, what TCP Flags are sent?
1) FIN - I’m ready to close the connection
2) ACK - I hear you
3) FIN - I am also ready to close the connection
4) ACK - Cool, let’s stop being connected
Every time a TCP connection is established, a ____________ occurs.
Three-way handshake
What TCP Flags in the correct order are involved in the Three-Way Handshake?
1) SYN - Let’s connect! Look at my sequence number field so we know where the conversation starts!
2) SYN/ACK - Sure, let’s connect! I acknowledge your sequence number!
3) ACK - I acknowledge your response, let’s start sending data!
What is POP?
Post Offic Protocol
A way for email clients to retrieve emails from a mail server before storing them locally. This is good for temporary or intermittent internet connections
What is an ethernet frame?
A data packet at the ethernet level, on the data link layer
What are two other names for the Data Link Layer in network models?
1) Network Interface Layer
2) Network Access Layer
Routers sharing data using __________ protocols are all under control of the same organization.
Interior Gateway Protocols
What is a Link State Protocol?
When all routers on an autonomous system share their state with eachother in order to determine the best routing path more quickly than distance-vector protocols
A device that knows how to forward data between independent networks on the network layer, is what?
A router!
What are the layers in the Fiver-Layer Network Model?
1) Physical Layer
2) Data Link Layer
3) Network Layer
4) Transport Layer
5) Application Layer
What does the Transport Layer do?
Sorts out which client and server programs are supposed to receive data
Name the 7 main parts of an Ethernet Frame
1) Preamble
2) Recipient MAC
3) Sender MAC
4) Ether Type Field
5) Data/Payload
6) Pad
7) FCS
What are the seven layers in the OSI Networking Model?
1) Physical Layer
2) Data Link Layer
3) Network Layer
4) Transport Layer
5) Session Layer
6) Presentation Layer
7) Application Layer
What are the two most common materials used in networking cables?
Copper and Fiber
What is the SFD?
Start Frame Delimiter
The last byte of the preamble in an Ethernet Frame, letting the receiving device know the preamble is over and actual frame contents will now follow
What are the two categories that make up Interior Gateway Protocols?
Link State Protocols
and
Distance-Vector Protocols
What does OSI stand for?
Open Systems Interconnection
Which network layers do switches and hubs belong to?
Switches belong to the Data Link Layer
Hubs belong to the Physical Layer
What is a Collision Domain?
A network segment where only one device can communicate at a time
What is the FCS?
Frame Check Sequence
A 32 bit (or 4 byte) number that represents the checksum value for an entire ethernet frame
What does DHCP stand for?
Dynamic Host Configuration Protocol
What are the 3 primary types in the IP Address Class Sytem?
Class A (1st Octet = 0-127)
Network ID = Octet 1, Host ID = Octets 2,3,4
Class B (1st Octet = 128-191)
Network ID = Octets 1,2, Host ID = Octets 3,4
Class C (1st Octet = 192-223)
Network ID = Octets 1,2,3, Host ID = Octet 4
Routers use ______________ protocols when they need to share information across different organizations
Exterior Gateway Protocols
What is an ASN?
Autonomous System Number
Numbers assigned to individual Autonomous Systems
What does ARP stand for?
Address Resolution Protocol
What is a multicast frame?
A network transmission sent to all devices on the network, but is accepted or discarded by each device depending on criteria other than their own MAC address
What port does DNS listen on?
53
What is an Authoritative Name Server?
It is responsible for the last 2 parts of any domain name, where a single organization may be responsible for DNS lookups
When a TLD name server receives a DNS lookup, what does it tell the computer performin the name lookup?
Which authoritative name server to contact for name resolution
What is a TLD?
Top Level Domain
The last part of any domain name (.com, .org etc)
What are Root Name Servers responsible for?
Directing queries from the recursive name server to the appropriate TLD server to match a domain name with an IP address
How many total Root Name Servers are there?
13
Which 2 types of DNS servers are generally provided by your ISP or Local Area Network to store known domain name lookups for a certain amount of time?
Caching Name Servers and Recursive Name Servers
What are the four main parts of a standard modern network configuration?
-IP Address
-Subnet Mask
-Gateway for a host
-DNS Server
What TCP socket state confirms the TCP connection is in working orer and that both sides are now free to send eachother data?
ESTABLISHED
What does a TCP socket state of SYN-RECEIVED mean?
A socket previously in a LISTEN state has received a synchronization request and has sent a SYN/ACK back. (Server side only)
The TCP socket state ___________, means a TCP socket is ready and waiting for invoming connections
LISTEN
(Server side only)
What are the 6 types of TCP Flags?
URG (Urgent)
ACK (Acknowledge)
PSH (Push)
RST (Reset)
SYN (Synchronize)
FIN (Finish)
What is the Application Layer?
It allows network applications to communicate in a way they understand
What is the Transport Layer?
It allows traffic to be directed to specific network applications
What is the TCP responsible for?
Reliable delivery of information from one network to another using a constant stream of acknowledgements
How many bits are there in an IPv6 address?
128 - Separated into 6 groups
What is CSMA/CD for?
Carrier Sense Multiple Access with Collision Detection
Ethernet protocol on the data link layer
Used to determine when the communication channels are clear and when a device is free to transmit data
What does the Network Layer do?
Allows different networks to communicate with eachother using devices known as routers
What is SMTP?
Simple Mail Transfer Protocol
A standard method of outgoing communication via email, sending messages to a mail server for relaying
(Using port 584 or 465)
What does URL stand for?
Uniform Resource Locator
What does a Firewall do?
Blocks traffic that meets a certain criteria such as a range of IPs or certain ports
What networking layer are Firewalls primarily used on?
The Transport Layer
In the transport layer, what is a Port?
A 16-bit number that’s used to direct traffic to specific servers/services running on a networked computer
What are multiplexing and demultiplexing?
(Transport Layer)
Multiplexing is when the nodes of the network direct traffic towards many different receiving services
Demultiplexing is when traffic all aimed at the same node is delivered to the proper receiving service
How many bits are reserved for TCP Flags?
6
Ports that are generally used to establish an outbound connection are known as ______ ports.
Ephemeral
Ports 1024-49151 are known as ________ ports.
Registered or User Ports
Ports 1-1023 are known as _________ ports.
System Ports
Which network layer is this:
Protocol = HTTP, SMTP, etc
Protocol Data Unit = Messages
Addressing = n/a
The Application Layer
Which network layer is this:
Protocol = IP
Protocol Data Unit = Datagram
Addressing = IP Address
The Network Layer
Which network layer is this:
Protocol = TCP/UDP
Protocol Data Unit = Segment
Addressing = Port Numbers
The Transport Layer