• • • The Internet protocol suite is the and set of used on the and similar. It is commonly known as TCP/IP because the foundational protocols in the suite are the (TCP) and the (IP). It is occasionally known as the Department of Defense (DoD) model, because the development of the networking method was funded by the through. The Internet protocol suite provides specifying how data should be packetized, addressed, transmitted,, and received. This functionality is organized into four which classify all related protocols according to the scope of networking involved.

From lowest to highest, the layers are the, containing communication methods for data that remains within a single network segment (link); the, providing between independent networks; the handling host-to-host communication; and the, which provides process-to-process data exchange for applications. Specifying the Internet protocol suite and many of its constituent protocols are maintained by the (IETF). The Internet protocol suite predates the, a more comprehensive reference framework for general networking systems. A, used for the first three-way transmission. Halloween Games For Adults. The Internet protocol suite resulted from research and development conducted by the Defense Advanced Research Projects Agency () in the late 1960s.

After initiating the pioneering in 1969, DARPA started work on a number of other data transmission technologies. In 1972, joined the DARPA, where he worked on both satellite packet networks and ground-based radio packet networks, and recognized the value of being able to communicate across both. In the spring of 1973,, the developer of the existing ARPANET (NCP) protocol, joined Kahn to work on open-architecture interconnection models with the goal of designing the next protocol generation for the ARPANET. By the summer of 1973, Kahn and Cerf had worked out a fundamental reformulation, in which the differences between local network protocols were hidden by using a common, and, instead of the network being responsible for reliability, as in the ARPANET, this function was delegated to the hosts. Cerf credits and, designer of the network, with important influences on this design. The protocol was implemented as the Transmission Control Program, first published in 1974.

Appropriate for all introductory-to-intermediate courses in computer networking, the Internet, or Internet applications; students need no background in networking, operating systems, or advanced mathematics. Leading networking authority Douglas Comer presents a wide-ranging, self-contained tour of the.

Initially, the TCP managed both transmissions and routing, but as the protocol grew, other researchers recommended a division of functionality into protocol layers. Advocates included of the University of Southern California's, who edited the (RFCs), the technical and strategic document series that has both documented and catalyzed Internet development. Postel stated, 'We are screwing up in our design of Internet protocols by violating the principle of layering.' Encapsulation of different mechanisms was intended to create an environment where the upper layers could access only what was needed from the lower layers. A monolithic design would be inflexible and lead to scalability issues. The Transmission Control Program was split into two distinct protocols, the Transmission Control Protocol and the Internet Protocol. The design of the network included the recognition that it should provide only the functions of efficiently transmitting and routing traffic between end nodes and that all other intelligence should be located at the edge of the network, in the end nodes.

This design is known as the. Using this design, it became possible to connect almost any network to the ARPANET, irrespective of the local characteristics, thereby solving Kahn's initial internetworking problem. One popular expression is that TCP/IP, the eventual product of Cerf and Kahn's work, can run over 'two tin cans and a string.' [ ] Years later, as a joke, the formal protocol specification was created and successfully tested. A computer called a is provided with an interface to each network.

It forwards back and forth between them. Originally a router was called gateway, but the term was changed to avoid confusion with other types of. [ ] Specification [ ] From 1973 to 1974, Cerf's networking research group at Stanford worked out details of the idea, resulting in the first TCP specification. A significant technical influence was the early networking work at, which produced the protocol suite, much of which existed around that time. DARPA then contracted with,, and the to develop operational versions of the protocol on different hardware platforms. Four versions were developed: TCP v1, TCP v2, TCP v3 and IP v3, and TCP/IP v4. The last protocol is still in use today.

In 1975, a two-network TCP/IP communications test was performed between Stanford and University College London (UCL). In November, 1977, a three-network TCP/IP test was conducted between sites in the US, the UK, and Norway. Several other TCP/IP prototypes were developed at multiple research centers between 1978 and 1983. The migration of the ARPANET to TCP/IP was officially completed on January 1, 1983, when the new protocols were permanently activated.

Adoption [ ] In March 1982, the US Department of Defense declared TCP/IP as the standard for all military computer networking. In 1985, the Internet Advisory Board (later renamed the ) held a three-day workshop on TCP/IP for the computer industry, attended by 250 vendor representatives, promoting the protocol and leading to its increasing commercial use. In 1985, the first conference focused on network interoperability by broader adoption of TCP/IP.

The conference was founded by Dan Lynch, an early Internet activist. From the beginning, large corporations, such as IBM and DEC, attended the meeting. Interoperability conferences have been held every year since then. Every year from 1985 through 1993, the number of attendees tripled. The Saint Meets The Tiger Ebook Store there. [ ] IBM, AT&T and DEC were the first major corporations to adopt TCP/IP, despite having competing internal protocols (,, ). In IBM, from 1984, 's group did TCP/IP development. (Appelman later moved to to be the head of all its development efforts.) They navigated the corporate politics to get a stream of TCP/IP products for various IBM systems, including,, and.

At the same time, several smaller companies began offering TCP/IP stacks for and, such as the company, and the. The first VM/CMS TCP/IP stack came from the University of Wisconsin. Some of these TCP/IP stacks were written single-handedly by a few programmers. Jay Elinsky and of IBM Research wrote TCP/IP stacks for VM/CMS and OS/2, respectively. In 1984 Donald Gillies at MIT wrote a 'ntcp' multi-connection TCP which ran atop the IP/PacketDriver layer maintained by John Romkey at MIT in 1983-4. Romkey leveraged this TCP in 1986 when FTP Software was founded.

Phil Karn created KA9Q TCP (a multi-connection TCP for ham radio applications) starting in 1985. The spread of TCP/IP was fueled further in June 1989, when AT&T agreed to place the TCP/IP code developed for into the public domain. Various vendors, including IBM, included this code in their own TCP/IP stacks. Many companies sold TCP/IP stacks for Windows until Microsoft released a native TCP/IP stack in Windows 95. This event was a little late in the evolution of the Internet, but it cemented TCP/IP's dominance over other protocols, which began to lose ground. These protocols included (SNA), 's, (OSI), and (XNS). Key architectural principles [ ] An early architectural document,, emphasizes architectural principles over layering.

The has evolved over time. Its original expression put the maintenance of state and overall intelligence at the edges, and assumed the Internet that connected the edges retained no state and concentrated on speed and simplicity. Real-world needs for firewalls, network address translators, web content caches and the like have forced changes in this principle. The states: 'In general, an implementation must be conservative in its sending behavior, and liberal in its receiving behavior. That is, it must be careful to send well-formed datagrams, but must accept any datagram that it can interpret (e.g., not object to technical errors where the meaning is still clear).' 'The second part of the principle is almost as important: software on other hosts may contain deficiencies that make it unwise to exploit legal but obscure protocol features.' Postel famously summarized the principle as, 'Be conservative in what you do, be liberal in what you accept from others'—a saying that came to be known as 'Postel's Law.'

Abstraction layers [ ]. Encapsulation of application data descending through the layers described in is used to provide abstraction of protocols and services.

Encapsulation is usually aligned with the division of the protocol suite into layers of general functionality. In general, an application (the highest level of the model) uses a set of protocols to send its data down the layers, being further encapsulated at each level. The layers of the protocol suite near the top are logically closer to the user application, while those near the bottom are logically closer to the physical transmission of the data. Viewing layers as providing or consuming a service is a method of to isolate upper layer protocols from the details of transmitting bits over, for example, and, while the lower layers avoid having to know the details of each and every application and its protocol. Even when the layers are examined, the assorted architectural documents—there is no single architectural model such as ISO 7498, the —have fewer and less rigidly defined layers than the OSI model, and thus provide an easier fit for real-world protocols. One frequently referenced document,, does not contain a stack of layers.

The lack of emphasis on layering is a major difference between the IETF and OSI approaches. It only refers to the existence of the internetworking layer and generally to upper layers; this document was intended as a 1996 snapshot of the architecture: 'The Internet and its architecture have grown in evolutionary fashion from modest beginnings, rather than from a Grand Plan. While this process of evolution is one of the main reasons for the technology's success, it nevertheless seems useful to record a snapshot of the current principles of the Internet architecture.' , entitled Host Requirements, is structured in paragraphs referring to layers, but the document refers to many other architectural principles not emphasizing layering. It loosely defines a four-layer model, with the layers having names, not numbers, as follows: • The application layer is the scope within which applications create user data and communicate this data to other applications on another or the same host. The applications, or processes, make use of the services provided by the underlying, lower layers, especially the Transport Layer which provides reliable or unreliable pipes to other processes.

The communications partners are characterized by the application architecture, such as the and networking. This is the layer in which all higher level protocols, such as,,,, operate. Processes are addressed via ports which essentially represent services. • The transport layer performs host-to-host communications on either the same or different hosts and on either the local network or remote networks separated by routers. It provides a channel for the communication needs of applications. UDP is the basic transport layer protocol, providing an unreliable datagram service. The Transmission Control Protocol provides flow-control, connection establishment, and reliable transmission of data.

• The internet layer has the task of exchanging datagrams across network boundaries. It provides a uniform networking interface that hides the actual topology (layout) of the underlying network connections.

It is therefore also referred to as the layer that establishes internetworking, indeed, it defines and establishes the Internet. This layer defines the addressing and routing structures used for the TCP/IP protocol suite. The primary protocol in this scope is the Internet Protocol, which defines. Its function in routing is to transport datagrams to the next IP router that has the connectivity to a network closer to the final data destination. • The link layer defines the networking methods within the scope of the local network link on which hosts communicate without intervening routers. This layer includes the protocols used to describe the local network topology and the interfaces needed to effect transmission of Internet layer datagrams to next-neighbor hosts.

The Internet protocol suite and the layered design were in use before the OSI model was established. Since then, the TCP/IP model has been compared with the OSI model in books and classrooms, which often results in confusion because the two models use different assumptions and goals, including the relative importance of strict layering.

This abstraction also allows upper layers to provide services that the lower layers do not provide. While the original OSI model was extended to include connectionless services (OSIRM CL), IP is not designed to be reliable and is a protocol. This means that all transport layer implementations must choose whether or how to provide reliability. UDP provides data integrity via a but does not guarantee delivery; TCP provides both data integrity and delivery guarantee by retransmitting until the receiver acknowledges the reception of the packet. This model lacks the formalism of the OSI model and associated documents, but the IETF does not use a formal model and does not consider this a limitation, as illustrated in the comment by, 'We reject: kings, presidents and voting. We believe in: rough consensus and running code.'

Criticisms of this model, which have been made with respect to the OSI model, often do not consider ISO's later extensions to that model. For multi-access links with their own addressing systems (e.g. Ethernet) an address mapping protocol is needed. Such protocols can be considered to be below IP but above the existing link system. While the IETF does not use the terminology, this is a subnetwork dependent convergence facility according to an extension to the OSI model, the internal organization of the network layer (IONL).

ICMP & IGMP operate on top of IP but do not transport data like UDP or TCP. Again, this functionality exists as layer management extensions to the OSI model, in its Management Framework (OSIRM MF) The SSL/TLS library operates above the transport layer (uses TCP) but below application protocols. Again, there was no intention, on the part of the designers of these protocols, to comply with OSI architecture. The link is treated as a black box.

The IETF explicitly does not intend to discuss transmission systems, which is a less academic [ ] but practical alternative to the OSI model. The following is a description of each layer in the TCP/IP networking model starting from the lowest level. Link layer [ ] The has the networking scope of the local network connection to which a host is attached. This regime is called the link in TCP/IP literature.

It is the lowest component layer of the Internet protocols, as TCP/IP is designed to be hardware independent. As a result, TCP/IP may be implemented on top of virtually any hardware networking technology. The link layer is used to move packets between the Internet layer interfaces of two different hosts on the same link. The processes of transmitting and receiving packets on a given link can be controlled both in the for the, as well as on or specialized. These perform functions such as adding a to prepare it for transmission, then actually transmit the frame over a.

The TCP/IP model includes specifications of translating the network addressing methods used in the Internet Protocol to link layer addresses, such as (MAC) addresses. All other aspects below that level, however, are implicitly assumed to exist in the link layer, but are not explicitly defined. This is also the layer where packets may be selected to be sent over a or other. In this scenario, the link layer data may be considered application data which traverses another instantiation of the IP stack for transmission or reception over another IP connection. Such a connection, or virtual link, may be established with a transport protocol or even an application scope protocol that serves as a in the link layer of the protocol stack. Thus, the TCP/IP model does not dictate a strict hierarchical encapsulation sequence.

The TCP/IP model's link layer corresponds to the Open Systems Interconnection (OSI) model physical and data link layers, layers one and two of the OSI model. Internet layer [ ] The has the responsibility of sending packets across potentially multiple networks. Requires sending data from the source network to the destination network. This process is called. The Internet Protocol performs two basic functions: • Host addressing and identification: This is accomplished with a hierarchical system. • Packet routing: This is the basic task of sending packets of data (datagrams) from source to destination by forwarding them to the next network router closer to the final destination.

The internet layer is not only agnostic of data structures at the transport layer, but it also does not distinguish between operation of the various transport layer protocols. IP carries data for a variety of different. These protocols are each identified by a unique: for example, (ICMP) and (IGMP) are protocols 1 and 2, respectively. Some of the protocols carried by IP, such as ICMP which is used to transmit diagnostic information, and IGMP which is used to manage data, are layered on top of IP but perform internetworking functions. This illustrates the differences in the architecture of the TCP/IP stack of the Internet and the OSI model. The TCP/IP model's internet layer corresponds to layer three of the Open Systems Interconnection (OSI) model, where it is referred to as the network layer.

The internet layer provides an unreliable datagram transmission facility between hosts located on potentially different IP networks by forwarding the transport layer datagrams to an appropriate next-hop router for further relaying to its destination. With this functionality, the internet layer makes possible internetworking, the interworking of different IP networks, and it essentially establishes the Internet. The Internet Protocol is the principal component of the internet layer, and it defines two addressing systems to identify network hosts' computers, and to locate them on the network. The original address system of the and its successor, the Internet, is (IPv4). It uses a 32-bit and is therefore capable of identifying approximately four billion hosts. This limitation was eliminated in 1998 by the standardization of (IPv6) which uses 128-bit addresses.

IPv6 production implementations emerged in approximately 2006. Transport layer [ ] The transport layer establishes basic data channels that applications use for task-specific data exchange.

The layer establishes process-to-process connectivity, meaning it provides end-to-end services that are independent of the structure of user data and the logistics of exchanging information for any particular specific purpose. Its responsibility includes end-to-end message transfer independent of the underlying network, along with,,,, and application addressing (). End-to-end message transmission or connecting applications at the transport layer can be categorized as either, implemented in TCP, or, implemented in UDP. For the purpose of providing process-specific transmission channels for applications, the layer establishes the concept of the.

This is a numbered logical construct allocated specifically for each of the communication channels an application needs. For many types of services, these have been standardized so that client computers may address specific services of a server computer without the involvement of service announcements or directory services. Because IP provides only a, some transport layer protocols offer reliability. However, IP can run over a reliable data link protocol such as the (HDLC).

For example, the TCP is a connection-oriented protocol that addresses numerous reliability issues in providing a: • data arrives in-order • data has minimal error (i.e., correctness) • duplicate data is discarded • lost or discarded packets are resent • includes traffic congestion control The newer (SCTP) is also a reliable, connection-oriented transport mechanism. It is message-stream-oriented—not byte-stream-oriented like TCP—and provides multiple streams multiplexed over a single connection. It also provides support, in which a connection end can be represented by multiple IP addresses (representing multiple physical interfaces), such that if one fails, the connection is not interrupted. It was developed initially for telephony applications (to transport over IP), but can also be used for other applications.

The User Datagram Protocol is a connectionless protocol. Like IP, it is a best effort, 'unreliable' protocol. Reliability is addressed through using a weak checksum algorithm. UDP is typically used for applications such as streaming media (audio, video, etc.) where on-time arrival is more important than reliability, or for simple query/response applications like lookups, where the overhead of setting up a reliable connection is disproportionately large. (RTP) is a datagram protocol that is designed for real-time data such as. The applications at any given network address are distinguished by their TCP or UDP port. By convention certain well known ports are associated with specific applications.

The TCP/IP model's transport or host-to-host layer corresponds to the fourth layer in the Open Systems Interconnection (OSI) model, also called the transport layer. Application layer [ ] The includes the protocols used by most applications for providing user services or exchanging application data over the network connections established by the lower level protocols. This may include some basic network support services such as protocols for routing and host configuration. Examples of application layer protocols include the (HTTP), the (FTP), the (SMTP), and the (DHCP). Data coded according to application layer protocols are into transport layer protocol units (such as TCP or UDP messages), which in turn use to effect actual data transfer. The TCP/IP model does not consider the specifics of formatting and presenting data, and does not define additional layers between the application and transport layers as in the OSI model (presentation and session layers).

Such functions are the realm of and. Application layer protocols generally treat the transport layer (and lower) protocols as which provide a stable network connection across which to communicate, although the applications are usually aware of key qualities of the transport layer connection such as the end point IP addresses and port numbers. Application layer protocols are often associated with particular applications, and common services have well-known port numbers reserved by the (IANA).

For example, the uses server port 80 and uses server port 23. Connecting to a service usually use, i.e., port numbers assigned only for the duration of the transaction at random or from a specific range configured in the application. The transport layer and lower-level layers are unconcerned with the specifics of application layer protocols. Routers and do not typically examine the encapsulated traffic, rather they just provide a conduit for it.

However, some and applications must interpret application data. An example is the (RSVP). It is also sometimes necessary for (NAT) traversal to consider the application payload.

The application layer in the TCP/IP model is often compared as equivalent to a combination of the fifth (Session), sixth (Presentation), and the seventh (Application) layers of the Open Systems Interconnection (OSI) model. Furthermore, the TCP/IP reference model distinguishes between user protocols and support protocols. Support protocols provide services to a system. User protocols are used for actual user applications. For example, FTP is a user protocol and DNS is a support protocol. Layer names and number of layers in the literature [ ] The following table shows various networking models.

This section does not any. Unsourced material may be challenged and. (March 2014) () The Internet protocol suite does not presume any specific hardware or software environment. It only requires that hardware and a software layer exists that is capable of sending and receiving packets on a computer network. As a result, the suite has been implemented on essentially every computing platform.

A minimal implementation of TCP/IP includes the following: (IP), (ARP), (ICMP), (TCP), (UDP), and (IGMP). In addition to IP, ICMP, TCP, UDP, Internet Protocol version 6 requires (NDP), ICMPv6, and IGMPv6 and is often accompanied by an integrated security layer. Application programmers are typically concerned only with interfaces in the application layer and often also in the transport layer, while the layers below are services provided by the TCP/IP stack in the operating system. Most IP implementations are accessible to programmers through and. Unique implementations include, an stack designed for, and, a stack and associated protocols for amateur systems and connected via serial lines. Microcontroller firmware in the network adapter typically handles link issues, supported by driver software in the operating system.

Non-programmable analog and digital electronics are normally in charge of the physical components below the link layer, typically using an (ASIC) chipset for each network interface or other physical standard. High-performance routers are to a large extent based on fast non-programmable digital electronics, carrying out link level switching. See also [ ]. • • • • (fast local Internet protocol stack) • • • • Bibliography [ ] •. Internetworking with TCP/IP – Principles, Protocols and Architecture. Davies and Thomas F. Microsoft Windows Server 2003 TCP/IP Protocols and Services.

• Forouzan, Behrouz A. TCP/IP Protocol Suite (2nd ed.). • Craig Hunt TCP/IP Network Administration. O'Reilly (1998) • Maufer, Thomas A.

IP Fundamentals. Prentice Hall.. • Ian McLean. Windows(R) 2000 TCP/IP Black Book. • Ajit Mungale Pro.NET 1.1 Network Programming. TCP/IP Illustrated, Volume 1: The Protocols.

• and Gary R. TCP/IP Illustrated, Volume 2: The Implementation. TCP/IP Illustrated, Volume 3:,,, and the Protocols. Computer Networks. SIGCOMM '88 Symposium proceedings on Communications architectures and protocols.: 106–114...

Retrieved 2011-10-16. References [ ]. •, Requirements for Internet Hosts – Communication Layers, R. Braden (ed.), October 1989. •, Requirements for Internet Hosts – Application and Support, R. Braden (ed.), October 1989 • Cerf, Vinton G. & Cain, Edward (1983),, Computer Networks, 7, North-Holland, pp. 307–318 • Cerf, Vinton G.

& Kahn, Robert E. (1974), (PDF), 5 • Internet Hall of Fame • Postel, Jon (1977), 'Section 3.3.3.2', •, Requirements for IP Version 4 Routers, F.

Baker (June 1995) •, Specification of Internet Transmission Control Protocol, V. (December 1974) •. Retrieved 12 September 2016. • Ronda Hauben.. TCP Digest (UUCP).

Retrieved 2007-07-05. Retrieved 12 September 2016.

• • Baker, Steven; Gillies, Donald W.. • Romkey, John (17 February 2011).. Retrieved 12 September 2016. • Karn, Phil.

'KA9Q TCP Download Website'. Missing or empty url= () •, Architectural Principles of the Internet, B. Carpenter (June 1996) •, Marjory S.

Blumenthal, David D. Clark, August 2001 • • • OSI: Reference Model Addendum 1: Connectionless-mode Transmission, ISO7498/AD1, ISO7498/AD1, May 1986 •, ISO 8648:1988. •, ISO 7498-4:1989. Richard Stevens, February 1994 •, Requirements for Internet Hosts – Communication Layers, 1.1.3 Internet Protocol Suite, 1989 • Dye, Mark; McDonald, Rick; Rufi, Antoon (29 October 2007).. Cisco Press..

Retrieved 12 September 2016 – via Google Books. • • Forouzan, Behrouz A.; Fegan, Sophia Chung (1 August 2003).. McGraw-Hill Higher Education.. Retrieved 12 September 2016 – via Google Books. • Comer, Douglas (1 January 2006)..

Prentice Hall.. Retrieved 12 September 2016 – via Google Books. • Kozierok, Charles M.

(1 January 2005).. No Starch Press.. Retrieved 12 September 2016 – via Google Books. • Stallings, William (1 January 2007)..

Prentice Hall.. Retrieved 12 September 2016 – via Google Books. • Tanenbaum, Andrew S. (1 January 2003)..

Prentice Hall PTR.. Retrieved 12 September 2016 – via Google Books. Meyer (December 2002),, Internet Engineering Task Force External links [ ] Wikiversity has learning resources about • – Pages on Robert Kahn, Vinton Cerf, and TCP/IP (reviewed by Cerf and Kahn). • – Specification of Internet Transmission Control Program, December 1974 Version • A TCP/IP Tutorial – from the Internet Engineering Task Force (January 1991) • • – A comprehensive look at the protocols and the procedures/processes involved • • • – Intro to TCP/IP LAN administration, conversational style • •.

Description Appropriate for all introductory-to-intermediate courses in computer networking, the Internet, or Internet applications; students need no background in networking, operating systems, or advanced mathematics. Leading networking authority Douglas Comer presents a wide-ranging, self-contained tour of the concepts, principles, and technologies that enable today’s Internet to support applications ranging from web browsing to telephony and multimedia. Comer begins by illuminating the applications and facilities offered by today’s Internet. Next, he systematically introduces the underlying network technologies and protocols that make them possible.

With these concepts and technologies established, he introduces several of the most important contemporary issues faced by network implementers and managers, including quality of service, Internet telephony, multimedia, network security, and network management. Comer has carefully designed this book to support both top-down and bottom-up teaching approaches. Students need no background in operating systems, and no sophisticated math: Comer relies throughout on figures, drawings, examples, and analogies, not mathematical proofs. Teaching and Learning Experience This program will provide a better teaching and learning experience—for you and your students. • Broad Coverage of Key Concepts and Principles, Presented in a Technology-independent Fashion: Comer focuses on imparting knowledge that students will need regardless of which technologies emerge or become obsolete.

• Flexible Organization that Supports both Top-down and Bottom-up Teaching Approaches: Chapters may be sequenced to accommodate a wide variety of course needs and preferences. • An Accessible Presentation that Resonates with Students: Comer relies throughout on figures, drawings, examples, and analogies, not mathematical proofs.

• A Companion Web Site that Enhances Learning: The web site for the text includes support material for both students and instructors. • Keep Your Course Current: Content is refreshed to provide the most up-to-date information on new technologies for your course.

Broad Coverage of Key Concepts and Principles, Presented in a Technology-independent Fashion • Drawing on more than 30 years’ experience at the leading edge of networking research and implementation, Comer focuses on imparting knowledge that students will need regardless of which technologies emerge or become obsolete. • Every chapter includes hands-on exercises and projects that offer opportunities for students to test their knowledge and gain confidence in their abilities. Flexible Organization that Supports both Top-down and Bottom-up Teaching Approaches • The text is organized into five parts. Chapters may be sequenced in multiple orders to accommodate a wide variety of instructor/student/course needs and preferences. • This text combines the best of top-down and bottom-up approaches. When presented in order, the book exposes students to applications and allows them to write network programs early, while delivering all material in logical order so a reader understands how each new technology builds on lower layer technologies.

An Accessible Presentation that Resonates with Students • No sophisticated mathematics is required—instead of formal mathematical proofs, Comer presents highly accessible examples, figures, drawings, and analogies. • The text answers the basic question: how do computer networks and Internets operate? It provides a comprehensive, self-contained tour through all of networking that describes applications, Internet protocols, network technologies, such as LANs and WANs, and low-level details, such as data transmission and wiring. It shows how protocols use the underlying hardware and how applications use the protocol stack to provide functionality for users.

A Companion Web Site that Enhances Learning • A web site for the text includes supporting material, such as photos of equipment, computer software, and lab exercises a reader can perform to reinforce concepts, as well as instructor materials, such as classroom presentations and copies of the figures. Keep Your Course Current In response to suggestions from readers and recent changes in networking, the new edition has been completely revised and updated. The significant changes include: • NEW!

Updates throughout each chapter • NEW! Additional figures to enhance explanations • NEW! Integration of IPv4 and IPv6 in all chapters • NEW! Improved coverage of MPLS and tunneling • NEW! New chapter on Software Defined Networking and OpenFlow • NEW! New chapter on the Internet of Things and Zigbee.

About the Author(s) Dr. Douglas Comer is an internationally recognized expert on TCP/IP protocols, computer networking, and the Internet. One of the researchers who contributed to the Internet as it was being formed in the late 1970s and 1980s, he was a member of the Internet Architecture Board, the group responsible for guiding the Internet's development. He was also chairman of the CSNET technical committee, a member of the CSNET executive committee, and chairman of DARPA's Distributed Systems Architecture Board.

Comer has consulted for industry on the design of computer networks. In addition to giving talks in US universities, each year Comer lectures to academics and networking professionals around the world. Comer's operating system, XINU, and implementation of TCP/IP protocols (both documented in his textbooks), have been used in commercial products. Comer is a Distinguished Professor of Computer Science at Purdue University.

He is currently on leave from Purdue, serving as VP of Research Collaboration at Cisco Systems. Recently, Comer has taught courses on networking, internetworking, computer architecture, and operating systems. He has developed innovative labs that provide students with the opportunity to gain hands-on experience with operating systems, networks, and protocols. In addition to writing a series of best-selling technical books that have been translated into 16 languages, he served as the North American editor of the journal Software — Practice and Experience for 20 years. Comer is a fellow of the ACM.