TCP

1. TCP/IP Suite

2. Default Gateway Gateway � a confusing terminology For our discussion about TCP/IP, gateway and router can be used interchangeably Default gateway: the IP address of the router port where the subnet is connected The router port belongs to the subnet that is configured for and connected to. When a user on a subnet wants to send data to another subnet, it actually sends it to the default gateway for delivery.

3. Default Gateway

4. DHCP DHCP: Dynamic Host Configuration Protocol The DHCP server can automatically assign IP addresses from a pool The device on the network seeks out the DHCP server for an IP address when a user wishes to explore the Internet DHCP is used by many Internet users as they go through their ISP (Internet Service Provider) The ISP assigns a valid IP address for a period of time (lease) to a customer as it logs into the system

5. DHCP

6. The Ping Command The Ping command is often used to test network and devices attached to the network A user types in the ping command and the IP address of the station to be tested An echo request message is sent from the source host This echo request message travels through the network to reach the destination The destination host then responds to the echo request The reply message include information such as the amount of time for return, the route taken, and the IP addresses of the router interfaces

7. Ping

8. ARP ARP (Address Resolution protocol) � to assist in determining the media access control (MAC) address of a device, given an IP address Each station maintains a table of IP address versus MAC address (in the cache) If the physical address of the destination station is not in the table, an ARP request message is broadcasted as an IP datagram (connectionless service) If a device recognizes the IP address, it returns an ARP reply message with its MAC address, which is then put in the ARP cache.

9. ARP in Action Device A types in the IP address of device C 172.20.10.4 using the TCP/IP ping command Device A�s TCP/IP stack scans the ARP cache. If no entry for 172.20.10.4 exists, device A�s TCP/IP stack creates an ARP request. An Ethernet broadcast is then sent out and is processed by each device that receives it (see Frame 1) Device D then provides its MAC address (see frame 2) Device A starts the ping (see frame 3) Device D replies with Frame 4

10. ARP in Action (I)

11. ARP in Action (II)

12. IP Version 6 The next generation of IP 128-bit addresses An encryption extension for better security A simplified header format Autoconfiguration support Authentication extension Do not have a firm implementation date yet

13. IP Version 6

14. Host-to-Host Layer Tied directly to the process layer above and to the Internet layer below Two ways to handle the host-to-host responsibilities TCP (connection-oriented protocol): A reliable transfer with information including sequence numbers, acknowledgement numbers, and error checking UDP (connectionless protocol): An unreliable data transfer with little or no procedures for verifying that data reaches the target safely

15. Host-to-Host Layer

16. The TCP Header

17. TCP/IP Ports TCP/IP applications use UDP and TCP to access the network Applications are identified by port numbers Well-known ports: numbers identify the application and have a value between 1 and 1023 Telnet: port 23 SMTP: port 24 FTP: port 21 TFTP: port 69 HTTP: port 80 Random ports: have values between 1025 and 65535 are assigned to users to allow applications to match the data to the correct session Sockets: IP address + the port number

18. TCP/IP Ports

19. The UDP Header Very little overhead in an attempt to achieve quick transfer of network traffic The traffic, however, could be lost UDP does not have the acknowledgements and sequence numbers used by TCP UDP messages are often called datagrams processes that utilize UDP: SNMP (Simple Network Management Protocol) RIP (routing Information Protocol) TFTP (Trivial File Transfer Protocol) BootP (Bootstrap Protocol

20. UTP Header

21. Process Layer - Applications The TCP/IP application or function being accomplished on the network Sending e-mail Browsing the WWW Some applications are designed with a high degree of network reliability (FTP), while others are designed to be quicker but less reliable (TFTP) Most applications on the server have a standard port number Port 23: Telnet Port 80: HTTP Port 21 FTP Each session client application is assigned a random port number between 1,025 � 65,534

22. Process Layer � Applications

23. FTP Vs. TFTP Both are applications providing computers with ability to access files on different devices FTP Utilizes TCP for host-to-host reliability Allows format specification such as ASCII or binary Allows authentication control Allows anonymous or guest users to access files TFTP Utilizes UDP Does not provide authentication

24. FTP

25. Telnet A remote access application which allows users to log into other host computers Allows a user at one site to establish a TCP connection with another host (mainframe or router) Passes the keystrokes from the user�s keyboard directly to the remote computer Carries output from the remote device back to the user�s screen Used by the networking professionals to accomplish tasks such as configuring a router at a remote location

26. Telnet

27. E-mail Offers users the ability to quickly send and receive messages from around the world The recipient of the message does not have to be connected to the network when the message is sent Messages are spooled to a server Two standard applications SMTP (Simple Mail Transfer Protocol): consists of a readable ASCII text messages MIME (Multipurpose Internet Mail Extensions): allows the transmission of non-ASCII data through e-mail

28. HTTP HTTP (HyperText Transfer Protocol) allows users on the WWW to access Web servers Uses a request/response protocol to obtain desired information The client software (user agent) sends a request, and the server sends a response (Netscape Navigator and Internet Explorer) Secure HTTP allows financial transactions to occur in a protected manner

29. HTTP

30. DNS Domain Name System (DNS) is a database used by TCP/IP applications to translate names and IP addresses No single domain name server knows all the names and IP addresses DNS uses a server tree to tie all the information together The �resolver� checks the local host file, then contacts the local domain name server, and continues to contact domain name servers until it locates the correct IP address

31. Organizational Domains

32. BootP BootP (Bootstrap Protocol) allows a device such as diskless workstation to obtain TCP/IP configuration information (IP address, default gateway, etc.) BootP sends its messages in UDP headers enclosed in IP datagrams A diskless workstation sends out a BootP request A BootP server answers with the desired configuration

33. BootP

34. SNMP Simple Network Management Protocol (SNMP) is a protocol for managing network using the TCP/IP protocol suite Allows a network consisting of components from different vendors to be managed from a single platform SNMP manager is a device on the network with the SNMP management software used to configure, monitor, and troubleshoot the network Routers, hubs, NICs, servers, and other devices can be managed by the SNMP manager SNMP can query devices about their status on an ongoing basis The agents can be configured to report back to the SNMP manager when certain conditions have been reached

35. SNMP