1. Communication Protocols III Tenth Meeting

2. Connections in TCP A wants to send to B. What is the packet next move? A travels through hub and bridge to router X X reads destination address (B) X know that B is through Z Which one is a valid route? 5 5 5 2 2 2 2

3. TCP States SYN ReceivedSYN Sent Listen Established Closed ACK SYN+ACK ACK Close RESET SYN SYN + ACK

4. TCP:Three Way Handshake Computer A Set sequence # = 100 (randomly) Sends SYN message Computer B Receives message Set sequence # = 259 (randomly) Set ACK sequence # = 101 Why? Sends SYN ACK Computer A Receive message Set ACK sequence # = 260 Why? Computer A Computer B Sequence # = 100 Acknowledgment # = 0 SYN Sequence # = 259 Acknowledgment # 101 SYN ACK Acknowledgment # 260 ACK

5. 434 TCP Sliding Window 12345678 Sent and already ACKed Sent not ACKed Can be sent ASAP Can’t be sent until window moves up 56783124123567856 Time Packets or (octets)

6. Network BIOS To connect a PC to a LAN, you need Network interface card (NIC), and LAN. The interface includes the address of the PC in the LAN. The netBIOS (network BIOS) Is part of the windows OS Communicate through the NIC to access the LAN. Provides an application program interface (API) for application programs to use the TCP/IP.

7. Network Operation System It is installed in a stand-alone PC It Has the following: a Redirector, Determine whether a request from the PC’s operating system is for a local or remote resource. a server message block (SMB) protocol, allows one computer (the client) to request resources such as files from another computer netBIOS and a TCP/IP protocol stack.

8. Server Message Block (SMB) The SMB peer-to-peer protocol defines four categories of messages: session control create and close a Redirector connection to a shared resource at a server. File are used by the Redirector to gain access to files at a server Printer used by the Redirector to send data to a print queue at a server and to get status information about the print queue message. allows an application to send messages to or receive messages from a server.