Tài liệu học CCNA kỳ 1 mod11 tranport and application layer

1 Module 11 Transport and Application Layer NIIT-ICT Hanoi info@niithanoi.vn Contents • TCP/IP Transport Layer • TCP/IP Application Layer 2 NIIT-ICT Hanoi info@niithanoi.vn Overview • The TCP/IP transport layer does the work of transporting data between applications on source and destination devices. • This module will describe the functions and services of this critical layer of the TCP/IP network model. • Many of the network applications that are found at the TCP/IP application layer are familiar to even casual network users. For example: HTTP, FTP and SMTP v.v NIIT-ICT Hanoi info@niithanoi.vn Introduction • Transport layer used to transport and regulate the flow of information from the source to the destination, reliably and accurately. End-to-end control and reliability are provided by sliding windows, sequencing numbers, and acknowledgments. 3 NIIT-ICT Hanoi info@niithanoi.vn Introduction to transport layer • The transport layer establishes a logical connection between the endpoints of the network. Transport services segment and reassemble several upper-layer applications onto the same transport layer data stream. • The transport layer defines end-to-end connectivity between host applications. Transport services include the following basic services: - Segmentation of upper-layer application data - Establishment of end-to-end operations - Transport of segments from one end host to another end host - Flow control provided by sliding windows - Reliability provided by sequence numbers and acknowledgments NIIT-ICT Hanoi info@niithanoi.vn Flow control • Flow control avoids the problem of a transmitting host overflowing the buffers in the receiving host. TCP provides the mechanism for flow control by allowing the sending and receiving host to communicate. The two hosts then establish a data-transfer rate that is agreeable to both. 4 NIIT-ICT Hanoi info@niithanoi.vn Multiplexing • Multiple applications can share the same transport connection in the OSI reference model. • Different applications can send data segments on a first-come, first- served basis. The segments that arrive first will be taken care of first. This is referred to as the multiplexing of upper-layer conversations. NIIT-ICT Hanoi info@niithanoi.vn Establishing a Connection • One function of the transport layer is to establish a connection- oriented session between similar devices at the application layer. For data transfer to begin, both the sending and receiving applications inform the respective operating systems that a connection will be initiated and the first handshake requests synchronization. 5 NIIT-ICT Hanoi info@niithanoi.vn Flow Control When datagrams arrive too quickly for a host or gateway to process and the transport function can issue a “not ready” indicator to the sender to stop sending data. When the receiver can handle additional data, the receiver sends a “ready” transport indicator. When this indicator is received, the sender can resume the segment transmission. NIIT-ICT Hanoi info@niithanoi.vn Three-way handshake • A three-way handshake is the synchronization process is required for the connection establish. Synchronization is done through an exchange of connection establishing segments that carry a control bit called SYN as in the figure. • The three-way handshake is necessary and is required in the connection-oriented connection. 6 NIIT-ICT Hanoi info@niithanoi.vn Windowing and Acknowledgment NIIT-ICT Hanoi info@niithanoi.vn Transmission Control Protocol (TCP) • Transmission Control Protocol provides reliable full-duplex data transmission. • TCP is responsible for breaking messages into segments, reassembling them at the destination station, resending anything that is not received, and reassembling messages from the segments, uses a virtual circuit between end-user applications. 7 NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: Port number • Source Port 16 bits. • Destination Port 16 bits. • Source Port 16 bits. • Destination Port 16 bits. 8 NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: Sequence • Sequence Number: 32 bits – The sequence number of the first data octet in this segment (except when SYN is present). • Sequence Number: 32 bits – The sequence number of the first data octet in this segment (except when SYN is present). NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: Acknowledgment • Acknowledgment Number: 32 bits – This field contains the value of the next sequence number the sender of the segment is expecting to receive. • Acknowledgment Number: 32 bits – This field contains the value of the next sequence number the sender of the segment is expecting to receive. 9 NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: Code bits • Control Bits: 8 bits – ACK: Acknowledgment field significant – RST: Reset the connection – SYN: Synchronize sequence numbers – FIN: No more data from sender • Control Bits: 8 bits – ACK: Acknowledgment field significant – RST: Reset the connection – SYN: Synchronize sequence numbers – FIN: No more data from sender NIIT-ICT Hanoi info@niithanoi.vn TCP Header format: Window • Window: 16 bits – The number of data octets beginning with the one indicated in the acknowledgment field which the sender of this segment is willing to accept. • Window: 16 bits – The number of data octets beginning with the one indicated in the acknowledgment field which the sender of this segment is willing to accept. 10 NIIT-ICT Hanoi info@niithanoi.vn TCP header fields • Source & Destination port – Number of the calling, called port • Sequence number – Number used to ensure correct sequencing of the arriving data • Acknowledgment number – Next expected TCP octet • HLEN – Number of 32-bit words in the header • Reserved – Set to zero • Code bits – Control functions, such as setup and termination of a session • Window – Number of octets that the sender is willing to accept • Checksum – Calculated checksum of the header and data fields • Urgent pointer – Indicates the end of the urgent data • Option – One option currently defined, maximum TCP segment size • Data – Upper-layer protocol data NIIT-ICT Hanoi info@niithanoi.vn User Datagram Protocol (UDP) • UDP is a simple protocol that exchanges datagrams, without acknowledgments or guaranteed delivery. Error processing and retransmission must be handled by higher layer protocols • UDP is designed for applications that do not need to put sequences of segments together [...]... Introduction to the TCP/IP application layer When the TCP/IP model was designed, the session and presentation layers from the OSI model were bundled into the application layer of the TCP model This means that issues of representation, encoding, and dialog control are handled in the application layer rather than in separate lower layers as in the OSI model NIIT-ICT Hanoi info@niithanoi.vn Domain Name System(DNS)... registered for vendor-specific applications Most of these are above 10 24 NIIT-ICT Hanoi info@niithanoi.vn TCP and UDP port numbers • End systems use port numbers to select the proper application The source host dynamically assigns originating source port numbers These numbers are always greater than 10 24 NIIT-ICT Hanoi info@niithanoi.vn 12 Introduction to the TCP/IP application layer When the TCP/IP model... to the upper layers Port numbers are used to keep track of different conversations crossing the network at the same time NIIT-ICT Hanoi info@niithanoi.vn 11 TCP and UDP port numbers • Application software developers agree to use well-known port numbers • • • that are issued by the Internet Assigned Numbers Authority (IANA) Numbers < 10 24 are considered well-known ports numbers Numbers > 10 24 are dynamically... network administrators to manage network performance, find and solve network problems, and plan for network growth SNMP uses UDP as its transport layer protocol NIIT-ICT Hanoi info@niithanoi.vn 16 Key Component of SNMP • Network management system (NMS) – NMS executes applications • • that monitor and control managed devices The bulk of the processing and memory resources required for network management are... information and translates that information into a form compatible with SNMP NIIT-ICT Hanoi info@niithanoi.vn Telnet Telnet client software provides the ability to login to a remote Internet host that is running a Telnet server application and then to execute commands from the command line NIIT-ICT Hanoi info@niithanoi.vn 17 Summary • • • • • • • • • • • The functions of the TCP/IP transport layer Flow... connection between peer systems Windowing Acknowledgment Transport layer protocols TCP and UDP header formats TCP and UDP port numbers The processes and protocols at the TCP/IP application layer Domain Name Services, File Transfer Protocols, Simple Mail Transfer Protocol Simple Network Management Protocol, Telnet NIIT-ICT Hanoi info@niithanoi.vn 18 ... bytes including header and data Checksum – Calculated checksum of the header and data fields Data – Upper -layer protocol data The protocols that use UDP include: - TFTP (Trivial File Transfer Protocol) - SNMP (Simple Network Management Protocol) - DHCP (Dynamic Host Control Protocol) - DNS (Domain Name System) NIIT-ICT Hanoi info@niithanoi.vn TCP and UDP port numbers • Both TCP and UDP use port (socket)... transfer files from one computer to another by copying and moving files from servers to clients, and from clients to servers NIIT-ICT Hanoi info@niithanoi.vn 14 Trivial File Transfer Protocol (TFTP) • TFTP is a connectionless service that uses User Datagram Protocol (UDP) TFTP is used on the router to transfer configuration files and Cisco IOS images and to transfer files between systems that support TFTP... configuration of a mail client, verify that the SMTP and POP or IMAP settings are correctly configured A good way to test if a mail server is reachable is to Telnet to the SMTP port (25) or to the POP3 port (11 0) NIIT-ICT Hanoi info@niithanoi.vn Simple Network Management Protocol (SNMP) The Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management... Managed devices – Managed devices are network nodes that contain an SNMP agent and that reside on a managed network Managed devices collect and store management information and make this information available to NMSs using SNMP Managed devices, sometimes called network elements, can be routers, access servers, switches, and bridges, hubs, computer hosts, or printers Agents – Agents are network-management . Transport and Application Layer NIIT-ICT Hanoi info@niithanoi.vn Contents • TCP/IP Transport Layer • TCP/IP Application Layer 2 NIIT-ICT Hanoi info@niithanoi.vn Overview • The TCP/IP transport layer. info@niithanoi.vn Introduction to the TCP/IP application layer When the TCP/IP model was designed, the session and presentation layers from the OSI model were bundled into the application layer of the TCP model • Acknowledgment • Transport layer protocols • TCP and UDP header formats • TCP and UDP port numbers • The processes and protocols at the TCP/IP application layer • Domain Name Services,