צוללים לתוך TCP/IP

1. צוללים לתוך TCP/IP גיא מזרחי guy@betternet.co.il

2. בדיקת TCP/IP • כדי לבדוק תקינות TCP/IP במחשב עלינו לבצע את הפעולות הבאות: • בדיקת קבלת או קיום כתובת IP בעזרת פקודת IPCONFIG • Ping 127.0.0.1 • Ping “Local IP” • Ping “Default Gateway” • Ping “Remote Host”

3. TCP/IP • הצגת סרטון TCP/IP של מיקרוסופט

4. Network Interface Technologies • IP over LAN: • Ethernet • Token Ring • ARCnet • FDDI • IP Over WAN: • Serial lines • Packet switched networks

5. IP Over LAN • כוללת בעיקר את Ethernet ו-Token Ring • רשתות LAN ו MAN באמצעות כבלים וסיבים אופטיים

6. IP Over WAN • Serial Line Internet Protocol (SLIP) – Low speed TCP/IP communication over serial interface • Point to Point Protocol (PPP) – data link protocol that provides increased security, configuration, error detection.

7. Address Resolution Protocol (ARP) • Responsible for obtaining hardware addresses of TCP/IP hosts on broadcast based networks. • Uses local broadcast of destination IP to get MAC address of destination. • The result stored in ARP cache

8. Internet Control Message Protocol (ICMP) • Reports error and control messages for IP • Feedback on specific conditions • ICMP carried as IP datagram and it is unreliable

9. Internet Group Management Protocol (IGMP) • Informs routers that hosts a specific multicast group are available on a given network • This information is passed to other routers so that each router that support multicast is aware of which host groups are on which network • It is passed as IP datagram and therefore are unreliable

10. Internet Protocol (IP) • Addresses and Routes Packets • Connectionless – No session is established • Nonguaranteed Delivery • Reliability is the responsibility of higher layer protocols and application • Fragments and Reassembles Packets

11. IP on the Router: • Decrements TTL • Fragments Large packets into smaller packets • Create New Header for each new packet - Flag - Fragment ID - Fragment offset • Calculates a new checksome • Obtains the hardware address of the next Router • Forwards the packet

12. Ports • Port – Each application identify itself with port number • Port can be number between 0-65536 • The client OS dynamically assigns port to request specific service • Well Known Server Side application are pre-assigned by IANA and do not change. • Look for the port list at windows NT based systems: %systemroot%\system32\drivers\etc Or check RFC 1700

13. Socket • Endpoint for network communication • An application create socket by specifying three items: IP of the host, Service type (tcp/udp ), used port. • An application can create socket and use it to send connectionless traffic to remote application or to connect it to another application socket. The data is reliably sent over this connection.

14. Transmission Control Protocol (TCP) • Connection Oriented – Session before passing data • Reliable Delivery – Sequence numbers and Acknowledgements (ACKs) • Byte Stream Communication • Uses port numbers as Endpoint to communicate

15. TCP Packet

16. TCP Three-Way Handshake • Needed for : • Synchronize the sending and receiving of segments • Inform the other side how much data is able to receive at once • Establish a virtual connection • The process: • Session request with SYN flag ON (Synchronization) • The receiver acknowledges the request by sending back – the synchronization flag is set to ON, A sequence number to indicate the starting byte for a segment it may send, and an acknowledgment with the byte sequence number of next segment it expects to receive. • The requesting host sends back a segment with the acknowledged sequence number and acknowledgment number.

17. TCP Three-Way Handshake

18. TCP Sliding Windows

19. User Datagram Protocol (UDP) • Connectionless – No session is established • Does not guarantee delivery (no sequence number or acks) • Reliability is the responsibility of the application • Uses port numbers as Endpoint to communicate

20. UDP Packet

21. TCP VS. UDP