The bits and Bytes of Computer Networking Flashcards
Protocol
A defined set of standards that computers must follow in order to communicate properly
Computer Networking
The name we’ve given to the full scope of how computers communicate with each other
Physical layer
Represents the physical devices that interconnect computers
Data link layer
Responsible for defining a common way of interpreting these signals so network devices can communicate
The Ethernet standards
also define a protocol responsible for getting data nodes on the same network or link
Network layer
Allows different networks to communicate with each other through devices known as routers.
Internetworks
A collection of networks connected together through routers, the most famous of these being the INTERNET
IP
is the heart of the internet and most smaller networks around the world.
Transport layer
Sorts out which client and server programs are supposed to get that data ( Transport Control Protocol is part of this layer)
Application layer
Application specific
Cables
Connect different devices to each other allowing data to be transmitted over them.
Common Network Cables are made of
Copper and Fiber
Copper Cables
Operate by Changing voltage to binary, the most common forms to copper twisted-paid cables used in networking are Cat5,Cat5e, and Cat6 cables. Cat is short form of category. Category has different amount of twists and twist pairs are arranged.
Crosstalk
When an electrical pulse on one wire is accidentally detected on another wire
Fiber optic cables
Contain individual optical fibers, which are tiny tubes made out of glass about the width of a human hair. Uses light to represent data. Usually can transmit data quicker but are more expensive.
Hub
A physical layer device that allows for connections from many computers are once. Are rare nowadays.
Collision domain
A network segment where only one device can communicate at a time. If multiple systems try sending data at the same time, the electrical pulses sent across the cable can interfere with each other.
Network Switch
More common than hubs nowadays. Originally known as a switching hub. A data Link device not a physical layer device.
Hubs and Switches
The primary devices used to connect computers on a single network, usually referred to as a LAN, or local area network.
Router
A device that knows how to forward data between independent networks. Operates at layer 3, network. Inspects IP data.
Border Gateway Protocol ( BGP)
Routers share data with each other via this protocol , which lets them learn about the most optimal paths to forward traffic.
Servers
Provide data to something requesting data.
Clients
The thing receiving the data.
Note on servers, clients and nodes
Almost all nodes are server and clients at some time. But we classify something as server or client based on the primary reason for its existence i.e to serve clients data for mail etc.
Bit
The smallest representation of data that a computer can understand; it’s a one or a zero.
Modulation
A way of varying the voltage of a charge moving across the cable. When used on computer network this kind of modulation is known as line coding.
Duplex communication ( Also known as Full Duplex)
The concept that information can flow in both directions across the cable.
Simplex communication ( Also known as Half Duplex)
This process is unidirectional
Ethernet as a protocol solved
the collision problem by using a technique known as carrier sense multiple access with collision detection.
CSMA/CD
User to determine when the communications channels are clear, and when a device is free to transmit data.
MAC address ( Media Access Control Address)
A globally unique identifier attached to an individual network interface. It’s a 48-bit number normally represented by six groupings of two hexadecimal numbers.
Hexadecimal
A way to represent numbers using 16 digits.
Octet
In computer networking, any number that can be represented by 8 bits.
Organizationally Unique Identifier ( OUI)
The first three octets of a MAC address ( allows you to identify the manufacturer)
Note on Mac Addresses
Ethernet uses MAC addresses to ensure that the data it sends has both an address for the machine that sent the transmission as well as the one the transmission was intended for.
Unicast
A unicast transmission is always meant for just one receiving address. If the least significant bit in the first octet of a destination address is set to zero, it means that ethernet frame is intended for only the destination address.
Multicast
If the least significant bit in the first octet of a destination address is set to one, it means you’re dealing with a multicast frame.
Data Packet
An all-encompassing term that represents any single set of binary data being sent across a network link
Ethernet frame
A highly structured collection of information presented in a specific order.
Preamble
8 bytes ( or 64 bits) long, and can itself be split into two sections.
Start frame delimiter ( SFD)
Signals to a receiving device that the preamble is over and that the actual frame contents will now follow.
Destination MAC address
The hardware address of the intended recipient
EtherType field
16 bits long and used to describe the protocol of the contents of the frame.
Vlan header
Indicates that the frame itself is what’s called a VLAN frame.
If a VLAN header is present,
the EtherType field follows it.
Virtual LAN ( VLAN)
A technique that lets you have multiple logical LANs operating on the same physical equipment.
Payload
In networking terms, is the actual data being transported, which is everything that isn’t a header.
Frame Check Sequence
A 4-byte(or 32-bit) number that represents a checksum value for the entire frame.
checksum value
is calculated by performing what’s known as cyclical redundancy check against the frame.
Cyclical Redundancy Check ( CRC)
An important concept for data integrity, and is used all over computing, not just network transmissions.
IP addresses belong to
networks, not to the devices attached to those networks.
In most cases, static IP addresses are
reserved for servers and network devices while dynamic IP addresses are reserved for clients
IP datagram
A highly structured series of fields that are strictly defined.
The most common version of IP is
version 4, or IPv4.
Header Length field
Almost always 20 bytes in length when dealing with IPv4
Service Type field
These 8 bits can be used to specify details about quality of service, or QoS, technologies
Total Length field
Indicates the total length of the IP datagram it’s attached to
Identification field
A 16-bit number that’s used to group messages together
The maximum size of a single datagram is the largest number you can represent with
16 bits 65535
If the total amount of data that needs to be sent is larger than what can fit in a single datagram,
the IP layer needs to split this data up into many individual packets.
Flag field
Used to indicate if a datagram is allowed to be fragmented, or to indicate that the datagram has already been fragmented.
Fragmentation
The process of taking a single IP datagram and splitting it up into several smaller datagrams
Time to live(TTL)field
An 8-bit field that indicates how many router hops a datagram can traverse before it’s thrown away
Protocol field
Another 8-bit field that contains data about what transport layer protocol is being used.
Header checksum field
A checksum of the contents of the entire IP datagram header
Ip options field
An optional field and is used to set special characteristics for datagrams primarily used for testing purposes.
Padding field
A series of zeros used to ensure the header is the correct total size.
IP addresses can be split into two sections:
The network ID and the host ID
Address class system
A way of defining how the global IP address space is split up
ARP
A protocol used to discover the hardware address of a node iwth a certain IP address
ARP table
A list of IP addresses and the MAC addresses associated with them
ARP table entries generally
expire after a short amount of time to ensure changes in the network are accounted for.
What happens to the TTL field of an IP datagram every time it reaches a router?
At every router hop, the TTL field is decremented by one until it reaches zero, causing the datagram to be discarded.
Incorrect subnetting setups are a common problem you might run into as an IT Support Specialist,
so it’s important to have a strong understanding of how it works
Subnet masks
32-bit numbers that are normally written out as four octets in decimal
A single 8-bit number
Can represent 256 different numbers, or more specifically , the numbers 0-255.
Two of the most important operators are
OR and AND
In computer logic, a 1 represents
true and a 0 represents a false
X OR Y = Z
If either X or Y is true, then Z is true; otherwise, it’s false.
1 OR 0 = 1
0 OR 0 = 0
Subnet mask
A way for a computer to use AND operators to determine if an IP address exists on the same network
Network ID in the address classes
8 bit = Class A
16 bit = Class B
24 bit = Class C
Demarcate
Set something off
Demarcation point
To describe where one network or system ends and another one begins
What does CIDR stands for?
Classless Inter-Domain Routing
Router
A network device that forwards traffic depending on the destination address of that traffic
Routing Table
is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. The routing table contains information about the topology of the network immediately around it.
Routing protocols
A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network
Routing protocols fall into two main categories:
interior gateway protocols and exterior gateway protocols.
interior gateway protocols are further split into two categories:
Link state routing protocols and distance vector protocols
Interior gateway protocols
Used by routers to share information within a single autonomous system
Autonomous system
A collection of networks that all fall under the control of a single network operator
In computer science, a LIST is know as a
VECTOR
Internet Assigned Numbers Authority(IANA)
A non-profit organization that helps manage things like IP address allocation
Along with managing IP address allocation, the IANA is also responsible for
ASN, or Autonomous System Number allocation
Autonomous System Number ( ASN)
Numbers assigned to individual autonomous systems.
Autonomous Systems do not deliver data between each other using IP addresses, but rather use a special globally unique Autonomous System Number (ASN) assigned by IANA. Originally a 16-bit number, the current ASNs are 32 bits, displayed as two 16-bit numbers separated by a dot.
Non-Routable Address Spaces
- 0.0.0/8
- 16.0.0/12
- 168.0.0/16
Request for Comments
RFCs started as a way for academics to discuss how their computers might talk to each other.
Router Protocols Include:
Routing Information Protocol (RIP)
Interior Gateway Protocol (IGRP)
Open Shortest Path First (OSPF)
Exterior Gateway Protocol (EGP)
Enhanced Interior Gateway Routing Protocol (EIGRP)
Border Gateway Protocol (BGP)
Intermediate System-to-Intermediate System (IS-IS)
On a Local Area Network, or LAN, what identification do nodes use to communicate with each other internally?
Physical MAC Addresses
What protocol communicates data between routers representing the edges of autonomous systems?
Exterior Gateway
A ________ is where one network ends and another begins.
Demarcation point
RC stands for
Request for Comments
The process of taking a large network and splitting it up into many individual and smaller subnetworks is known as ________.
subnetting
An ARP broadcast is sent to the special MAC address ________.
FF:FF:FF:FF:FF:FF
What protocol is used to discover the hardware address of a node with a certain IP address?
ARP is a simple query–response packet protocol used to match workstations hardware addresses to IP addresses. In other words, ARP is the protocol used to identify nodes in a LAN.
What is the process of taking a large network and splitting it up into many individual and smaller subnetworks called?
Subnetting
