1. PJC CCNA Semester 2 Ver. 3.0 by William Kelly
Intermediate TCP/IP
PJC CCNA Semester 2 Ver. 3.0 by
William Kelly

2. The TCP/IP Protocol Suite
Standard for Internetwork Communications
TCP/IP closely maps to the OSI model and is helpful in understanding other protocols
TCP/IP includes layer 3 and 4 protocols as well as upper layer protocols

3. OSI vs. TCP

4. Common TCP Protocols DNS – Domain Name Server
WINS – Windows Naming Service
HOSTS – Static IP mapping file
POP3 – Post Office Protocol
SMTP – Simple Mail Transfer Protocol
FTP – File Transfer Protocol
TFTP – Trivial File Transfer Protocol
HTTP – Hypertext Transfer Protocol

5. Troubleshooting Protocols
Telnet - used for testing the application layer
Packet Internet Groper (ping) – used for lower layer testing
traceroute – used to find a break in the internetwork path between the source and the destination networks

6. Windows Troubleshooting Protocols
NBSTAT- used to troubleshoot NETBIOS name resolution
NETSTAT – useful to summarize TCP/IP connections
ipconfig/winipcfg – displays the current network settings (IP address of host, mask, gateway, and DNS information)

7. Transport Layer key points
Protocols (TCP and UDP)
Flow Control/Windowing
Data Reliability
3-way handshakes
Denial of Service
Ports

8. Layer 4: Transport Layer TCP vs. UDP
Connection-oriented
Reliable
Messages divided into segments
Reassembles at destination
Resends data that is not acknowledged
Connectionless
Unreliable
Messages are called datagrams
Software checking of message delivery
No reassembly of messages
No acknowledgements
No Flow Control

9. Transport Layer Protocols: TCP Segment Format

10. Transport Layer Protocols: UDP Segment Format
Notice port numbers are used in the formation of both UDP and TCP segments

11. Flow Control and Windowing
Flow control is the regulation of how much data is sent during a transmission period and windowing is the process of flow control
TCP breaks down large pieces of data into segments suitable for transmission
Windows size determines how many segments can be sent before acknowledgement
A sliding window adjusts the number of segments sent to cope with congestion or slow processing by the destination host

12. Data Reliability Reliability is provided in 3 ways: Sliding windows
Controls the amount of information transferred
Congestion avoidance and control
Allows more than one segment to be sent before acknowledgement
Positive acknowledgement with retransmission
Synchronization
Sequence numbers
Sequencing of segments at source before transmission

13. 3 Way Handshakes
TCP allows a synchronization process prior to data transmission that forms a virtual circuit
Sequence numbers included in the handshake assure that positive acknowledgements can be made to the connection request and to transmitted segments (Remember IP provides no verification that data was transmitted successfully)

14. 3 Way Handshakes (cont.)

15. Denial of Service Attacks During Synchronization
Syn Flooding is one type of DOS that uses a false source IP address during a 3 way handshake causing a reply to a non-existent address. This fills up the connection queue and exhausts system resources. Possible defenses include:
Decreasing the connection timeout
Increasing the size of the connection queue

16. Ports
Ports are represented by a 16 bit number ( 0 -65,535 possible)
Three types of ports are:
Well Known – 0 – 1023
Registered – 1024 – 49,151
Dynamic or Private – 49,152 – 65,535
A port number and an IP address for a socket
Usually clients randomly assign source port numbers
Note: Numbers below 255 are for public applications, numbers between 255 and 1023 are assigned to companies for marketable applications, and numbers above 1023 are unregulated

17. Important Port Numbers!!

18. Internet Layer Protocols
IP – connectionless best-effort system to move datagrams to a destination
ICMP – Provides control and messaging
ARP – Address Resolution Protocol determines a MAC address for a known IP address
RARP – Reverse Address Resolution Protocol determines an IP address for a known MAC address (diskless workstations)