These slides contain the information presented in our weekly meeting regarding OSI and QUIC.

2. Let’s connect these two computers, :-? obviously we need one RJ45 cable, yeah, very
easy.
Please connect these two computers, one iMac and the other one is Chromebook. O_o
Please Connect this printer too. -_-
We need common instructions and models to communicate.
How computers communicate with each other ?

3. In order to successfully communicate between computers in 1984 ISO has been
released current seven-layer OSI model.
OSI Project has begun from 1970, what happened exactly in these 14 years?
The OSI model was first defined in raw form in Washington, DC in February 1978 by Hubert Zimmermann
NPL network in the UK | ARPANET in the US | CYCLADES in France
International Telegraph and Telephone Consultative Committee --- X.200
International Organization for Standardization --- ISO 7498
1977 1983
OSI

4. TCP/IP
Internet Protocol Suit, started on 1960
They Defined a protocol stack to the world. Who?
funded by the United States Department of Defense through DARPA(Defence
Advanced Research Projects Agency).
1977, tested between three sites US, UK, Norway.
1982, TCP/IP as the standard for all military computer networking
1983, when the new protocols were permanently activated

5. OSI Model -> Open Systems Interconnection model
It’s just conceptual and actually it has not been implemented. 🤔
Application
Presentation
Session
Transport
Network
Data Link
Physical
Defines how data is transferred from one computer to another computer.

7. Please Do Not Throw Sausage Pizza Away
1 2 3 4 5 6 7

8. OSI is a model to how communicate, so we have internet and we have TCP/IP protocol suit.
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Transport
Internet
Network Access (Link Layer)

9. OSI Model Protocol Data Unit
Application Data
Presentation
Session
Transport Segment
Network Packets
DataLink Frames
Physical Bits

10. OSI Model Protocols
Application HTTP, TLS, DNS, DHCP, TELNET, SSH, SMTP, IMAP, POP, ...
Presentation
Session
Transport TCP / UDP
Network IPV4, IPV6, ICMP, IPSEC
DataLink ARP, MAC, ETHERNET 802.3, ETHERNET 802.11, PPP,
L2TP, SONET/SDH
Physical

11. OSI Model Devices
Application Firewalls
Presentation
Session
Transport Layer 4 firewalls
Network Router, multilayer, Switch, Wireless router
DataLink Switch, bridge, network interface card, wireless access point
Physical (media) Hub, NIC, wireless access point, cables and wires

12. Application Layer
Network Applications: softwares that use internet
File Transfer Web Surfing Emails Virtual Terminals
FTP HTTP / HTTPS SMTP Telnet

13. Presentation Layer
Translation Compression Encryption / Decryption
Transform Data to ASCI
and encode them / binary
Lossy / Lossless SSL

14. Session Layer
Setting and managing connections and ports.
Establish and terminate connections
Authentication and Authorization, Logging
When Data packets are coming, session layer takes care of which data type is
related to which data packet.

15. Transport Layer
Segmentation Flow Control Error Control
Create segments from raw
data and memories which
segment is related to which
application.
Control the amount of data
that being transferred.
- Automatic repeat
request technique.
- Checksum
TCP - Transmission Control Protocol UDP - User Datagram Protocol
Connection Oriented Transmission Connectionless Oriented Transmission
Hand Shaking No feedback
reliable unreliable
HTTP, FTP Movies, Games, Songs, VOIP, DNS

16. Network Layer
Works for transmitting data from between computers in different networks
Logical Addressing Routing Path determination
IPv4, IPv6, Mask
Append IP and mask to
segment and make packet
With IP and Mask that
sticked to the packet,
routing decisions are made.
Choosing the best and
fastest path to reach
destination computer

17. Data Link Layer
Physical Addressing: Append mac addresses and create frame protocol data unit
Access The Media (Framing) Error Detection
Controls how data is placed and received
from the media.
MAC - Media Access Control
CSMA and CSMA/CD
We need ARP Here.

18. Physical Layer
1
0

19. OSI Model Function
Application - Applications, protocols and services that interface with the end user
- Data is formatted, converted, encrypted decrypted compressed and decompressed and sent or presented to the user (MIME types)
- Open, close and manage a session between end-user application processes (RPC)Presentation
Session
Transport - Facilitates the programs want to communications on different ports and allows for multiplexing or multiple services to be set over the
wire simultaneously
- Reliable and unreliable end-to-end data transport and data stream services (TCP, UDP, SCTP)
- Connection oriented, connectionless communications, and data stream services(session establishment and termination)
Network - Provide host addressing (IP) logical addressing
- Choose the best path to the destination network (Routing)
- Switch packets out of the correct interface (Forwarding)
- Maintain quality of service (QoS)(Guarantee bandwidth)
- Connectionless end-to-end networking(connection part has been handled by Transport layer)
DataLink - 2 sublayers:
- Logical Link Control (LLC, 802.2) provides services to the upper layers
- Media Access Control (MAC) defines how devices access the medium
CSMA/CD, CSMA/CA, Token Passing
Host addressing (MAC addressing)
- Layer 2 Framing
- Error Checking
Physical Bits, signals, electrical pulses. Encoding ones and zeros

20. encapsulating : making packets
decapsulation : taking packets and put them back together and make data
Moving from 7 to 1
Moving from 1 to 7

21. Transport
Header
Data
Network
Header
Data
Data
Transport
Header
Source and destination port numbers
Source and destination IP Address
Transport
Header
Data
Network
Header
Source and destination MAC address
Frame Header Frame Trailer
Error checking
Application Layer
Transport Layer
Internet Layer
Your Email or Image or etc
Data
Transport
Header Data
Transport
Header
Network
Access
Layer
data
segments
Frames
Packets
Bits
1010101010101010101010101010101

22. An OSI Model for Cloud

23. Cisco AnyConnect
is a software application for connecting to virtual private networks based on Internet Key Exchange version 2.
Internet Protocol Security (IPsec)
is a secure network protocol suite that authenticates and encrypts the packets of data to provide
secure encrypted communication between two computers over an Internet Protocol network.
Internet Key Exchange
is the protocol used to set up a security association in the IPsec protocol suite.
Diffie–Hellman key exchange
is a method of securely exchanging cryptographic keys over a public channel and was one of the first
public-key protocols.
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys
RSA (Rivest–Shamir–Adleman)

24. Multiplexed Stream Protocol

25. QUIC - HTTP3?
Taken to the IETF 2015
Working group started 2016
Google deployed htt2 frames over UDP in 2013
We need transport protocol and another layer in application layer.

26. QUIC Improvements
TCP Head of line blockings
HandShaking
Earlier data
Connection ID - QUIC doesn’t use IP even more
More Encryptions than TLS

27. QUIC ON TOP OF UDP
UDP QUIC
Connectionless Uses UDP like tcp uses IP
Unreliable Is reliable
No resend data Resend data
No flow control Flow control

28. QUIC Streams
After connection established we have streams in our connection.
Streams are basically like HTTP2 but we have them in transport layer.
Many logical flows within a single connection
Independent streams

29. Applications in top layer of QUIC
First Protocol is HTTP
Other protocols are waiting for publish QUIC like DNS or WEBRTC
HTTP will handle data in binary over multiplexed QUIC

30. IP
UDPTCP
QUIC + TLS 1.3
TLS
HTTP/1.1 HTTP/2
HTTP/3
Streams

31. HTTP/2 HTTP/3
Transport TCP QUIC
Streams HTTP/2 QUIC
Clear-text version Yes No
Independent streams No Yes
Server Push Yes Yes
Early data Yes (In theory) Yes
Zero handshake No Yes

32. We call the HTTPS with https://
How to access HTTP3?
Alt-Svc: response header could tell the browser that the resource server
with HTTP/3 is also available for **** seconds in this port number in the
same origin.
IT’S A THEORY

33. HTTP3 Current Challenges
3-7% of QUIC attempts fail.
Clients need fallback algorithms
CPU intensive
Unoptimized UDP stacks -- linux
Funny TLS Layer - v1.3
All QUIC stacks are user-land and they have lot of implementations
No Standard QUIC API yet
Lack of tooling, All of softwares and tools works with TCP and the old mechanism -- wireshark

34. https://docs.google.com/document/d/1RNHkx_VvKWyWg6Lr8SZ-saqsQx7rFV-
ev2jRFUoVD34/edit#heading=h.nvk2biis6bpk
https://www.sciencedirect.com/topics/computer-science/presentation-
layer#:~:text=Layer%206%3A%20Presentation&text=by%20the%20application.-
,Protocol%20translation%2C%20the%20conversion%20of%20data%20from%20one%20protocol%20to,operating
%20systems%2C%20takes%20place%20here.
https://daniel.haxx.se/http3-explained/
https://blogs.cisco.com/cloud/an-osi-model-for-cloud