Networking Fundamentals Flashcards
Name the Layers to OSI 7-Layer model
- physical
- Datalink
- Network
- Transport
- Session
- Presentation
- Application
Layer 2 Data Link
- runs on top of layer 1
- devices at L2 have unique hardware (MAC) address
- Frames (containers for information) can be addressed to a destination or broadcasted
- CSMA(carrier sense multiple access) -senses if data is already be transmitted
Layer 1 Physical
the transmission and reception of raw bit streams between a device on a shared physical medium.
Drawbacks to Layer 1 Physical of the OSI 7-Layer model
- layer 1 has no media access control and no collision detection
- no device addressing all data is processed by all device
Switch
L2
- Maintains a mac address table which over time learns what computer is connected to what port
- Only valid frames are stored and forwarded
- Collisions are isolated on the port they occurred
- Every Port is a separate collision domain
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Layer 3 Network
Internet Protocol (IP) - adds cross-network IP addressing and routing to move data between local area networks without direct P2P links
IP Packets are moved step by step from source to destination via intermediate networks. Encapsulated in different frames along the way
IP Packet Structure
- Similar to frame in that they contain data to be moved and contain source and destination address
- as they move through networks they are placed inside frames specific to the local network that changes every time the packet moves through the network
- the IP Packet itself never changes
ARP
- Address Resolution Protocol
- finds the Mac address for this IP
Route
where the IP packet is forwared
Route Roles
multiple routes
Router
moves packet from SRC to DST encapsulating in L2 on the way
Cons of Layer 3
No method for channels of communications src IP ≤=> dst IP only
can be delivered out of order
no flow of control → if the source transmit faster than the destination IP saturating the destination causing packet loss
Layer 4 Transportation / Layer 5 Session
TCP - Transmission Control Protocol
- reliability, error correction, and ordering for data/slower
- connection oriented protocol → you have to set up a connection between two devices once setup creates bidirectional methods of communication
UDP- User Datagram Protocall
- faster less reliable
*Both run on top of IP and use IP as transit
Subnet Mask
used by Host to determine if an IP address it needs to communicate with is local or remote - which influences if it needs to use a gateway or can communicate locally
Network Address Translation (NAT)
- Translates private IPv4 addresses to public
- Designed to overcome IPv4 Shortages
- Static NAT- 1 private to 1 (fixed )public address(IGW)
- Dynamo NAT- 1 private to 1st Available Public
Who originally managed IPv4 Addresses and who manages them now?
originally managed by IANA(internet Assigned Numbers Authority) now managed by reginal authorities
When was IPv4 created?
created in 1981
What is the full range of IPv4 Addresses?
0.0.0.0 → 255.255.255.255
IP Address Range 1
- 10.0.0.0 - 10.225.255.255 (1 x Class A Network)
- 1,677,215 IPv4 addresses
- Private range that is usually used for cloud networks and is usually chopped up into sub networks
IP address Range 2
- 172.16.0.0 - 172.31.255.255(16 x class B Networks)
- 16x 65,536 IPv4 Address
- Usually Broken into smaller subnets
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IP address Range 3
- 192.168.0.0 - 192.168.255.255(256 x C class networks)
- 256x 256 IPv4 addresses
- usually used for home and small office networks
Communications between two overlapping IP Ranges
- If you have a need to connect private networks together and they user the same network address you would have issues with configurations
Static Network Address Translation
- The router (NAT Device) maintains a NAT table, it maps PrivateIP : Public IP(1:1)
Port Address Translation (PAT)
The NAT Device records the source(private)IP and source port. it replaces the source IP with the single Public IP and a public source port allocated from a pool which allows IP overloading(many to one)
Dynamic Network Address Translation
The router(NAT Device) maintains a Nat table, it maps Private IP: Public IP Public IP allocations are temporary allocations from a Public IP Pool.
IP Subnetting
subnetting the process of talking a larger network, and breaking it into more smaller networks(higher prefix)
Distributed Denial of Service (DDOS)
- Attacks designed to overload Websites
- Compete against ‘Legitimate Connections’
DDOS- Application Layer Attack
- it’s cheep for clients to make requests but computationally expensive for servers to deliver
- Legitimate User of the application can’t access the website because they have to compete for access with the attack
- performance reduce to failure levels
DDOS - Protocol Attack
a network of devices called Botnets are user to generate a hug number of spoofed SYN’s(connection Initiations). The serve sees these as normal and sends SYN-ACK’s back to the spoofed IPS
the serves will wait for an ACK which never happens
the serve consume available network resources attempting to establish connections
DDOS - Volumetric /Amplification Attack
A botnet exploits a protocol where a response is larger than the request
botnet make a spoofed request to DNS
The DNS server respond to the ‘spoofed IP’ , the frontend servers of out application becomes overwhelmed by the amount of data.
SSL and TLS (newer)
- privacy and Data integrity between client and server
- Privacy - communication are encrypted
- asymmetric and symmetric
- Identity (serve or client/server) Verified
- Reliable connection - protect against alternation
