Introduction to TCP/IP Networking

• Chapter 1 introduces TCP/IP networking.
• The objectives include perspectives on networking, the TCP/IP networking model, and data encapsulation terminology.

Two Major Branches of Networking

• Enterprise networks are one of the major branches.

TCP/IP Networking Model

• The TCP/IP model has evolved from proprietary models to an open standard.
• In the 1980's, networking was dominated by proprietary models like IBM and DEC.
• By the 2000's TCP/IP became prominent, becoming the standard.

TCP/IP Networking Models

• The original TCP/IP model has four layers: Application, Transport, Internet, and Link.
• The updated TCP/IP model consists of five layers: Application, Transport, Network, Data Link, and Physical layers.

TCP/IP Architectural Model and Example Protocols

• Application Layer protocols include HTTP, POP3, and SMTP.
• Transport Layer protocols are TCP and UDP.
• Internet Layer protocols include IP and ICMP.
• Data Link and Physical Layer protocols are Ethernet, 802.11 (Wi-Fi), and TCP/IP.

HTTP (Hypertext Transfer Protocol)

• HTTP involves a Web server (Larry) and a Web browser (Bob).
• The browser requests a web page from the server.
• The server responds with the requested file.

HTTP Request, Reply, and Data

• The browser sends an HTTP Get Request for a page.
• The server replies with an HTTP header indicating "OK" and the "home.htm" data.
• Additional data can be sent in subsequent messages.

TCP/IP Transport Layer

• It provides error-recovery services to HTTP.
• TCP assigns sequence numbers to data packets.
• If a packet is lost, TCP requests the next packet.

Same-Layer and Adjacent-Layer Interaction

• Same-layer interaction involves two computers communicating using a protocol.
• The protocol defines a header that communicates what each computer wants to do.
• Adjacent-layer interaction, a lower layer provides a service to the layer just above and implents the function.

Routing

• Postal service forwarding illustrates routing principles.

Simple TCP/IP Network

• Components include devices with IP addresses and routers.

Basic Routing Example

• Data packets are forwarded (routed) through networks.

Ethernet

• Ethernet for IP Packet Forwarding to Router.
• The letters LH and LT stand for link header and link trailer, respectively, and refer to the data link layer header and trailer.
• An IP packet is encapsulated into an ethernet frame and decapsulated by the destination.

Data Encapsulation

• Step 1: Data
• Step 2: TCP
• Step 3: IP
• Step 4: Data Link
• Step 5: Physical

Perspective on Encapsulation and Data

• The TCP segment includes TCP and Data.
• The IP packet includes IP and Data.
• The Ethernet frame includes LH (Link Header), Data, and LT (Link Trailer).

OSI Networking Model

• The OSI model has 7 layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical.
• The TCP/IP model collapses the Application, Presentation, and Session layers into a single Application layer.
• The OSI model's Network layer corresponds to the Internet layer in TCP/IP.The Link layer of TCP/IP combines Data Link and Physical layers from the OSI model.

OSI Reference Model Layer Definitions

• Application Layer: Provides an interface for communication software and applications, defining processes for user authentication.
• Presentation Layer: Defines and negotiates data formats like ASCII, EBCDIC, JPEG, also defining encryption as a service.
• Session Layer: Defines how to initiate, control, and terminate conversations (sessions).
• Transport Layer: Provides a range of services.
• Network Layer: Defines logical addressing, routing (forwarding), and path determination on how devices forward packets.
• Data Link Layer: Defines the rules for when a device can send data over a medium and the format of headers and trailers.
• Physical Layer: Specifies the physical characteristics of the transmission medium.

OSI Reference Model Devices and Protocols

• Application Layer: Uses protocols like Telnet, HTTP, FTP, SMTP, SNMP; devices include hosts and firewalls.
• Transport Layer: Uses TCP and UDP; devices are hosts and firewalls.
• Network Layer: Uses IP; the primary device is a router.
• Data Link Layer: Uses Ethernet(IEEE 802.3) and HDLC; devices include LAN switches, wireless access points, and modems.
• Physical Layer: Uses RJ-45 and Ethernet (IEEE 802.3); uses LAN hubs, LAN repeaters, and cables.

OSI Encapsulation and Protocol Data Units

• At L7: L7Header + Data = L7PDU
• At L6: L6Header + Data = L6PDU
• At L5: L5Header + Data = L5PDU
• At L4: L4Header + Data = L4PDU
• At L3: L3Header + Data = L3PDU
• At L2: L2Header + Data + L2Trailer = L2PDU