Protocols and Models PDF

Protocols and Models ITEC 90 - NETWORK FUNDAMENTALS  Objective 01 The Rules 05 Reference Models 02 Protocols 06 Data Encapsulation 03 Protocol Suites 07 Data Access 04 Standards Organizations The Rules  Commu...

Protocols and Models ITEC 90 - NETWORK FUNDAMENTALS  Objective 01 The Rules 05 Reference Models 02 Protocols 06 Data Encapsulation 03 Protocol Suites 07 Data Access 04 Standards Organizations 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.  Communications Protocols All communications are governed by protocols. Protocols are the rules that communications will follow. These rules will vary depending on the protocol.  Sample 2 Sample 1  Rule Establishment Individuals must use established rules or agreements to govern the conversation. The first message is difficult to read because it is not formatted properly. The second shows the message properly formatted Rule Establishment  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  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  Message Encoding Encoding is the process of converting information into another acceptable form for transmission. Decoding reverses this process to interpret the information.  Sample 2 Sample 1  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.  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.  Message Timing Message timing includes the following: 1. 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. 2. Response Timeout – Manages how long a device waits when it does not hear a reply from the destination. 3. Access method - Determines when someone can send a message.  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.  A Note About the Node Icon Documents may use the node icon , typically a circle, to represent all devices. The figure illustrates the use of the node icon for delivery options. Protocols  Network Protocol Overview Network protocols define a common set of rules. Can be implemented on devices in: Software Hardware Both Protocols have their own: Function Format Rules  Protocol Type 1. Network Communications - enable two or more devices to communicate over one or more networks. 2. Network Security - secure data to provide authentication, data integrity, and data encryption. 3. Routing - enable routers to exchange route information, compare path information, and select best path. 4. Service Discovery - used for the automatic detection of devices or services  Network Protocol Functions Devices use agreed-upon protocols to communicate. Protocols may have may have one or functions.  Network Protocol Functions 1. Addressing - Identifies sender and receiver 2. Reliability - Provides guaranteed delivery 3. Flow Control - Ensures data flows at an efficient rate 4. Sequencing - Uniquely labels each transmitted segment of data 5. Error Detection - Determines if data became corrupted during transmission 6. Application Interface - Process-to-process communications between network applications  Protocol Interaction Networks require the use of several protocols. Each protocol has its own function and format.  Protocol 1. Hypertext Transfer Protocol (HTTP) - It governs the way a web server and a web client interact and it also defines content and format. 2. Transmission Control Protocol (TCP) - It manages the individual conversations, provides guaranteed delivery and manages flow control. 3. Internet Protocol (IP) - Delivers messages globally from the sender to the receiver. 4. Ethernet - Delivers messages from one NIC to another NIC on the same Ethernet Local Area Network (LAN) 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 Network 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. Evolution of Protocol Suites  TCP/IP Protocol Example TCP/IP protocols operate at the application, transport, and internet layers. The most common network access layer LAN protocols are Ethernet and WLAN (wireless LAN).  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 TCP/IP Protocol Suite  TCP/IP Communication Process A web server encapsulating and sending a web page to a client. A client de-encapsulating the web page for the web browser  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.  Internet Standards 1. Internet Society (ISOC) - Promotes the open development and evolution of internet 2. Internet Architecture Board (IAB) - Responsible for management and development of internet standards 3. Internet Engineering Task Force (IETF) - Develops, updates, and maintains internet and TCP/IP technologies 4. Internet Research Task Force (IRTF) - Focused on long- term research related to internet and TCP/IP protocols  Internet Standards Standards organizations involved with the development and support of TCP/IP Internet Corporation for Assigned Names and Numbers (ICANN) Coordinates IP address allocation, the management of domain names, and assignment of other information Internet Assigned Numbers Authority (IANA) Oversees and manages IP address allocation, domain name management, and protocol identifiers for ICANN Internet Standards Electronic and Communications Standards Institute of Electrical and Electronics Engineers (IEEE, pronounced “I-triple-E”) dedicated to creating standards in power and energy, healthcare, telecommunications, and networking. Electronic Industries Alliance (EIA) - develops standards relating to electrical wiring, connectors, and the 19-inch racks used to mount networking equipment Electronic and Communications Standards Telecommunications Industry Association (TIA) - develops communication standards in radio equipment, cellular towers, Voice over IP (VoIP) devices, satellite communications, and more. International Telecommunications Union-Telecommunication Standardization Sector (ITU-T) - defines standards for video compression, Internet Protocol Television (IPTV), and broadband communications, such as a digital subscriber line (DSL) 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  The Benefits of Using a Layered Model 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  The OSI Reference Model 7 - Application - Contains protocols used for process-to- process communications. 6 - Presentation - Provides for common representation of the data transferred between application layer services. 5 - Session - Provides services to the presentation layer and to manage data exchange. 4 - Transport - Defines services to segment, transfer, and reassemble the data for individual communications.  The OSI Reference Model 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.  The TCP/IP Reference Model TCP/IP Model 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.  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. OSI and TCP/IP Model Comparison 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. Segmenting Messages  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.  Protocol Data Units Encapsulation is the process where 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: - Data (Data Stream) - Segment - Packet - Frame - Bits (Bit Stream) Protocol Data Units  Encapsulation Example Encapsulation is a top down process. The level above does its process and then passes it down to the next level of the model. This process is repeated by each layer until it is sent out as a bit stream. Encapsulation Example  De-encapsulation Example Data is de-encapsulated as it moves up the stack. When a layer completes its process, that layer strips off its header and passes it up to the next level to be processed. This is repeated at each layer until it is a data stream that the application can process. 1. Received as Bits (Bit Stream) 2. Frame 3. Packet 4. Segment 5. Data (Data Stream) De-encapsulation Example 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. Addresses  Layer 3 Logical Address The IP packet contains two IP addresses: Source IP address - The IP address of the sending device, original source of the packet. Destination IP address - The IP address of the receiving device, final destination of the packet. These addresses may be on the same link or remote. Layer 3 Logical Address  Layer 3 Logical Address An IP address contains two parts: Network portion (IPv4) or Prefix (IPv6) The left-most part of the address indicates the network group which the IP address is a member. Each LAN or WAN will have the same network portion. Host portion (IPv4) or Interface ID (IPv6) The remaining part of the address identifies a specific device within the group. This portion is unique for each device on the network. Layer 3 Logical Address  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  Role of the Data Link Layer Addresses: Same IP Network When devices are on the same Ethernet network the data link frame will use the actual MAC address of the destination NIC. MAC addresses are physically embedded into the Ethernet NIC and are local addressing. The Source MAC address will be that of the originator on the link. The Destination MAC address will always be on the same link as the source, even if the ultimate destination is remote. Role of the Data Link Layer Addresses: Same IP Network  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?  Role of the Network Layer Addresses When the source and destination have a different network portion, this means they are on different networks. PC1 – 192.168.1 Web Server – 172.16.1  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.  Role of the Data Link Layer Addresses: Different IP Networks The data link addressing is local addressing so it will have a source and destination for each link. The MAC addressing for the first segment is : Source – AA-AA-AA-AA-AA-AA (PC1) Sends the frame. Destination – 11-11-11-11-11-11 (R1- Default Gateway MAC) Receives the frame. Note: While the L2 local addressing will change from link to link or hop to hop, the L3 addressing remains the same.  Data Link Addresses Since data link addressing is local addressing, it will have a source and destination for each segment or hop of the journey to the destination. The MAC addressing for the first segment is: Source – (PC1 NIC) sends frame Destination – (First Router- DGW interface) receives frame  Data Link Addresses The MAC addressing for the second hop is: Source – (First Router- exit interface) sends frame Destination – (Second Router) receives frame  Data Link Addresses Notice that the packet is not modified, but the frame is changed, therefore the L3 IP addressing does not change from segment to segment like the L2 MAC addressing. The L3 addressing remains the same since it is global and the ultimate destination is still the Web Server.  Thank You Reference: Cisco