Layer 4
Transport Layer
- "Shipping and receiving docks"
- They help you with handling data and getting from one point to another reliably.
- End-to-end data transfer
- Flow control
- Segmentation / reassembly
- Errors
- TCP (Transmission Control Protocol) has built-in capabilities to handle errors.
- UDP (User Datagram Protocol) is usually used for real time applications because i notices that there is an error and it keeps track of it, and if you have a lot of errors it can lower the quality to make it an easier stream to deliver, but for the most part errors are OK in UDP.
- Tunneling
- IPSec ESP (Encapsulating Security Payload)
- This is what we use to handle encrypted data
- Confidential tunneling
- GRE (Generic Router Encapsulation)
- Clear text tunneling
- IPSec ESP (Encapsulating Security Payload)
- Management & diagnostics
- ICMP is a diagnostic protocol, sometimes if you ever try to use
ping, if it's there it comes back and tell us that's an ICMP request and an ICMP reply.
- ICMP is a diagnostic protocol, sometimes if you ever try to use
Data Transfer
- Applications use "sockets"
-
Apache: TCP / 443 / HTTPS
-
Bind: UDP / 53 / DNS
- Bind is a Domain Name Service (DNS) working using UDP for velocity.
-
Transmission Control Protocol (TCP)
- Connection-based
- Reliable
- Detail-oriented
-
User Datagram Protocol (UDP)
- Connectionless
- Unreliable
- Low overhead
- Typically lower the quality to prioritize speed
-
Tunneling
- Packets in packets
- A tunnel is a connection between two sides
- Back in the day we used huge and long cables to connect to part of the world
- Nowadays we tunnel over the internet
- Encrypted data is sent from one side to the other via tunneling.
- When we encrypt this packages we are putting them into other packages.
- VPN = Tunneling
- Common protocols include:
- ESP
- Encapsulating Security Payload
- IPsec VPN
- If you need encryption or more privacy use ESP
- Encapsulating Security Payload
- GRE
- Generic Routing Encapsulation
- GRE Tunneling
- ESP
Routing Protocols & Diagnostics
- Network Reachability
- Open Shortest Path First (OSPF)
- Enhanced Interior Gateway Routing Protocol (EIGRP)
- The fastest, initially Cisco propietary.
- TCP/ UDP (BGP/RIP)
- BGP is the protocol of the Internet, the entire internet runs in BPG version 4, it's one big network that's it's protocol.
- BGP is classified as an exterior gateway protocol.
- Interior gateway is INSIDE your network where you'll usually use OSPF and EIGRP
- Diagnostics
- Internet Control Message Protocol (ICMP)