Chapter2.pdf

Module 3: Protocols and Models Introduction to Networks 7.0 (ITN) Module Objectives Module Title: Protocols and Models Module Objective: Explain how network protocols enable devices to access local and remote network resources. Topic Title Topic Objective The Rules...

Module 3: Protocols and Models Introduction to Networks 7.0 (ITN) Module Objectives Module Title: Protocols and Models Module Objective: Explain how network protocols enable devices to access local and remote network resources. Topic Title Topic Objective The Rules Describe the types of rules that are necessary to successfully communicate. Protocols Explain why protocols are necessary in network communication. Protocol Suites Explain the purpose of adhering to a protocol suite. Standards Organizations Explain the role of standards organizations in establishing protocols for network interoperability. Reference Models Explain how the TCP/IP model and the OSI model are used to facilitate standardization in the communication process. Data Encapsulation Explain how data encapsulation allows data to be transported across the network. Data Access Explain how local hosts access local resources on a network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 3.1 The Rules © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 The Rules Communications Fundamentals Networks can vary in size and complexity. It is not enough to have a connection, devices must agree on “how” to communicate. There are three elements to any communication: There will be a source (sender). There will be a destination (receiver). There will be a channel (media) that provides for the path of communications to occur. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 The Rules Communications Protocols All communications are governed by protocols. Protocols are the rules that communications will follow. These rules will vary depending on the protocol. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 The Rules Rule Establishment Protocols must account for the following requirements: An identified sender and receiver Common language and grammar Speed and timing of delivery Confirmation or acknowledgment requirements © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 The Rules Network Protocol Requirements Common computer protocols must be in agreement and include the following requirements: Message encoding Message formatting and encapsulation Message size Message timing Message delivery options © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 The Rules Message Encoding Encoding is the process of converting information into another acceptable form for transmission. Decoding reverses this process to interpret the information. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 The Rules Message Formatting and Encapsulation When a message is sent, it must use a specific format or structure. Message formats depend on the type of message and the channel that is used to deliver the message. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 The Rules Message Size Encoding between hosts must be in an appropriate format for the medium. Messages sent across the network are converted to bits The bits are encoded into a pattern of light, sound, or electrical impulses. The destination host must decode the signals to interpret the message. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 The Rules Message Timing Message timing includes the following: Flow Control – Manages the rate of data transmission and defines how much information can be sent and the speed at which it can be delivered. Response Timeout – Manages how long a device waits when it does not hear a reply from the destination. Access method - Determines when someone can send a message. There may be various rules governing issues like “collisions”. This is when more than one device sends traffic at the same time and the messages become corrupt. Some protocols are proactive and attempt to prevent collisions; other protocols are reactive and establish a recovery method after the collision occurs. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 The Rules Message Delivery Options Message delivery may one of the following methods: Unicast – one to one communication Multicast – one to many, typically not all Broadcast – one to all Note: Broadcasts are used in IPv4 networks, but are not an option for IPv6. Later we will also see “Anycast” as an additional delivery option for IPv6. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 3.2 Protocols © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Protocols Network Protocol Overview Network protocols define Protocol Type Description a common set of rules. Can be implemented on devices in: Network enable two or more devices to communicate over Communications one or more networks Software Hardware Network Security secure data to provide authentication, data integrity, and data encryption Both Protocols have their own: Routing enable routers to exchange route information, compare path information, and select best path Function Format Service used for the automatic detection of devices or Rules Discovery services © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 Protocols Network Protocol Functions Devices use agreed-upon protocols to communicate. Protocols may have one or functions. Function Description Addressing Identifies sender and receiver Reliability Provides guaranteed delivery Flow Control Ensures data flows at an efficient rate Sequencing Uniquely labels each transmitted segment of data Error Detection Determines if data became corrupted during transmission Application Interface Process-to-process communications between network applications © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 Protocols Protocol Interaction Networks require the use of several protocols. Each protocol has its own function and format. Protocol Function Hypertext Transfer ▪ Governs the way a web server and a web client interact Protocol (HTTP) ▪ Defines content and format Transmission Control ▪ Manages the individual conversations Protocol (TCP) ▪ Provides guaranteed delivery ▪ Manages flow control Internet Protocol (IP) Delivers messages globally from the sender to the receiver Ethernet Delivers messages from one NIC to another NIC on the same Ethernet Local Area Network (LAN) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 3.3 Protocol Suites © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 Protocol Suites Network Protocol Suites Protocols must be able to work with other protocols. Protocol suite: A group of inter-related protocols necessary to perform a communication function Sets of rules that work together to help solve a problem The protocols are viewed in terms of layers: Higher Layers Lower Layers- concerned with moving data and provide services to upper layers © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 Protocol Suites Evolution of Protocol Suites There are several protocol suites. Internet Protocol Suite or TCP/IP- The most common protocol suite and maintained by the Internet Engineering Task Force (IETF) Open Systems Interconnection (OSI) protocols- Developed by the International Organization for Standardization (ISO) and the International Telecommunications Union (ITU) AppleTalk- Proprietary suite release by Apple Inc. Novell NetWare- Proprietary suite developed by Novell Inc. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 Protocol Suites TCP/IP Protocol Suite TCP/IP is the protocol suite used by the internet and includes many protocols. TCP/IP is: An open standard protocol suite that is freely available to the public and can be used by any vendor A standards-based protocol suite that is endorsed by the networking industry and approved by a standards organization to ensure interoperability © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20 Protocol Suites TCP/IP Communication Process A web server encapsulating and sending a A client de-encapsulating the web page for web page to a client. the web browser © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21 3.4 Standards Organizations © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22 Standards Organizations Open Standards Open standards encourage: interoperability competition innovation Standards organizations are: vendor-neutral non-profit organizations established to develop and promote the concept of open standards. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23 3.5 Reference Models © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24 Reference Models The Benefits of Using a Layered Model Complex concepts such as how a network operates can be difficult to explain and understand. For this reason, a layered model is used. Two layered models describe network operations: Open System Interconnection (OSI) Reference Model TCP/IP Reference Model © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25 Reference Models The Benefits of Using a Layered Model (Cont.) These are the benefits of using a layered model: Assist in protocol design because protocols that operate at a specific layer have defined information that they act upon and a defined interface to the layers above and below Foster competition because products from different vendors can work together Prevent technology or capability changes in one layer from affecting other layers above and below Provide a common language to describe networking functions and capabilities © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 26 Reference Models The OSI Reference Model OSI Model Layer Description 7 - Application Contains protocols used for process-to-process communications. Provides for common representation of the data transferred between application 6 - Presentation layer services. 5 - Session Provides services to the presentation layer and to manage data exchange. Defines services to segment, transfer, and reassemble the data for individual 4 - Transport communications. 3 - Network Provides services to exchange the individual pieces of data over the network. 2 - Data Link Describes methods for exchanging data frames over a common media. 1 - Physical Describes the means to activate, maintain, and de-activate physical connections. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 27 Reference Models The TCP/IP Reference Model TCP/IP Model Description Layer Application Represents data to the user, plus encoding and dialog control. Transport Supports communication between various devices across diverse networks. Internet Determines the best path through the network. Network Access Controls the hardware devices and media that make up the network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 28 Reference Models OSI and TCP/IP Model Comparison The OSI model divides the network access layer and the application layer of the TCP/IP model into multiple layers. The TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium. OSI Layers 1 and 2 discuss the necessary procedures to access the media and the physical means to send data over a network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 29 3.6 Data Encapsulation © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 30 Data Encapsulation Segmenting Messages Segmenting is the process of breaking up messages into smaller units. Multiplexing is the processes of taking multiple streams of segmented data and interleaving them together. Segmenting messages has two primary benefits: Increases speed - Large amounts of data can be sent over the network without tying up a communications link. Increases efficiency - Only segments which fail to reach the destination need to be retransmitted, not the entire data stream. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 31 Data Encapsulation Sequencing Sequencing messages is the process of numbering the segments so that the message may be reassembled at the destination. TCP is responsible for sequencing the individual segments. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 32 Data Encapsulation Encapsulation is the process where Protocol Data Units protocols add their information to the data. At each stage of the process, a PDU has a different name to reflect its new functions. There is no universal naming convention for PDUs, in this course, the PDUs are named according to the protocols of the TCP/IP suite. PDUs passing down the stack are as follows: 1. Data (Data Stream) 2. Segment 3. Packet 4. Frame 5. Bits (Bit Stream) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 33 3.7 Data Access © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 34 Data Access Addresses Both the data link and network layers use addressing to deliver data from source to destination. Network layer source and destination addresses - Responsible for delivering the IP packet from original source to the final destination. Data link layer source and destination addresses – Responsible for delivering the data link frame from one network interface card (NIC) to another NIC on the same network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 35 Data Access Devices on the Same Network When devices are on the same network the source and destination will have the same number in network portion of the address. PC1 – 192.168.1.110 FTP Server – 192.168.1.9 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 36 Data Access Devices on a Remote Network What happens when the actual (ultimate) destination is not on the same LAN and is remote? What happens when PC1 tries to reach the Web Server? Does this impact the network and data link layers? © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 37 Data Access Role of the Data Link Layer Addresses: Different IP Networks When the final destination is remote, Layer 3 will provide Layer 2 with the local default gateway IP address, also known as the router address. The default gateway (DGW) is the router interface IP address that is part of this LAN and will be the “door” or “gateway” to all other remote locations. All devices on the LAN must be told about this address or their traffic will be confined to the LAN only. Once Layer 2 on PC1 forwards to the default gateway (Router), the router then can start the routing process of getting the information to actual destination. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 38