1. Nachos
Theoretical Presentation 3
Teammates:
Jorge
Jose
Daniel
Ricardo

2. Network Protocol
Defines rules and conventions for communication between
network devices.
● Ethernet
● ARP
● IP
● UDP
● TCP
● CAN
● SSH

3. UDP Protocol
Used to communicate (unreliable) between application
programs in a network.
UDP header.
Source port and destination port identifies the process that
sends a receives the data in the UDP packet.
The IP protocol needs network address to send the data to the
correct host in the network and needs a port number to send
the data to the correct program application.

4. Well-known ports
There's a list of currently assigned ports to some services, so
when you need to use a port number you must remember to
avoid those numbers.
Port number Name
22 SSH
23 Telnet
88 Kerberos
80 HTTP
194 IRC

5. UDP Properties
Does not need acknowledge.
It's not a reliable network protocol, that's why the messages
can be:
● lost
● arrive out of order
● duplicated
Does not provide feedback to control the rate at which
information flows between the machines.

6. TCP Protocol
TCP is a reliable connection oriented protocol, which means
that:
● data it's received in the same order that was send.
● detects duplicated data.
● retransmits lost data.
TCP header

7. Establishing a TCP connection

8. Closing a TCP connection

9. Ping response delay
Google facebook and wikipedia takes more time to ack
a packet send than yahoo and twitter.
Ps: test realized at 11 pm.

10. Likelihood packet will be dropped.

11. Emulating lost packed.

12. Planning practical implementation
Nachos already send packets in order but it's protocol is not
reliable.
So with that in mind we propose build a protocol similar to TCP
in top of the nachos one.
The program for testing the new protocol will be a ping or a
chat.

13. Network Security
Confidence information and services available on a network
cannot be accessed by unauthorized users.
There's two fundamental techniques that form the basis for the
internet security:
● Perimeter security
● encryption
Perimeter security allows an organization to determine the
services and networks it will make available to outsiders and
the extend to which outsiders can use resources.

14. Aspects of information security
● Data Integrity
● Data Availability
● Privacy Or Confidentiality
● Authorization
● Autentication
● Replay Avoidance

15. Internet Security
Source authentication (accepts requests from computers on a
authorized list) is a weak security method.
Stronger authentication requires encryption.

16. IPsec
Provides a set of security algorithms and a general framework
that allows a security communication .

17. HMAC algorithm

18. Firewall
Blocks all unauthorized communication between computers in
the organization and computers outside the organization.
Monitoring:
● a firewall notifies a manager whenever an incident occurs
(active monitoring).
● a firewall logs a record of each incident in a file on disk
(passive monitoring).

19. Planning practical implementation
Some security in nachos programs execution and
comunication:
● Implement a list of nachos machines authorized to
communicate with.
● Implement a list of users (id's) authorized to execute
useprog programs.

20. DHCP
The Dynamic Host Configuration Protocol (DHCP) service
enables devices on a network to obtain IP addresses and
other information from a DHCP server. This service automates
the assignment of IP addresses, subnet masks, gateway and
other IP networking parameters.

21. Static Assignment of Addresses
With a static assignment, the network administrator must
manually configure the network information for a host, as
shown in the figure. At a minimum, this includes entering
the host IP address, subnet mask, and default gateway.

22. Dynamic Assignment of Addresses
DHCP enables the automatic assignment of addressing
information such as IP address, subnet mask, default
gateway, and other configuration information.

23. DNS
Domain Name Service Protocol (DNS) is used to resolve
Internet names to IP addresses.

24. DNS protocol communications use a single format called a
message. This message format is used for all types of client
queries and server responses, error messages, and the
transfer of resource record information between servers.