IT Network Module 3 PDF

Chapter 3- Protocols and Models ◦3.1 Rules of Communication ◦3.2 Protocols and Standards ◦3.3 Protocol Suite ◦3.5 Reference Model ◦3.6 Data Encapsulation ◦3.7 Data Access 3.1 –Rules for communication The Rules :Communications Fundamentals Networks can vary in size and complexity. It is not enough...

Chapter 3- Protocols and Models ◦3.1 Rules of Communication ◦3.2 Protocols and Standards ◦3.3 Protocol Suite ◦3.5 Reference Model ◦3.6 Data Encapsulation ◦3.7 Data Access 3.1 –Rules for communication 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.  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. Protocols for different communications are different. The Rules: Rule Establishment (Cont.) 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 The Rules: Rule Establishment (Cont.) 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 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 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. (Animation- 3.1.6) 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. (Animation -3.1.7) The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation. De-encapsulation occurs when the process is reversed. The Rules :Message Size ◦ when a long message is sent from one host to another over a network, it is necessary to break the message into smaller pieces. ◦ At the receiving host, the individual pieces of the message are reconstructed into the original message.(Animation 3.1.8) 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. 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. “Anycast” is an additional delivery option for IPv6. 3.2 - Protocols Protocols :Network Protocol Overview Protocol Type Description Network protocols define a common set of rules. Network enable two or more devices to communicate Can be implemented Communication over one or more networks s on end devices and intermediary devices Network secure data to provide authentication, data in: Security integrity, and data encryption ◦ Software ◦ Hardware Routing enable routers to exchange route information, compare path information, and select best ◦ Both path Service used for the automatic detection of devices or Discovery services Protocols :Network Protocol Functions Network communication protocols are responsible for a variety of functions necessary for network communications between end devices. Computers and network devices use agreed-upon protocols to communicate. Protocols may have may have one or functions as listed below: Function Description Addressing Identifies sender and receiver (IPv4 and IPv6) Reliability Provides guaranteed delivery(TCP) Flow Control Ensures data flows at an efficient rate (TCP) Sequencing Uniquely labels each transmitted segment of data (TCP) Error Detection Determines if data became corrupted during transmission( IPv4, IPv6 & TCP) Application Interface Process-to-process communications between network applications(HTTP/HTTPs) 3.3 Protocol Suites Protocol Suites : Network Protocol Suites A protocol suite is a group of inter-related protocols necessary to perform a communication function. These inter-related protocols are viewed in terms of layers: ◦ each higher-level service depending on the functionality defined by the protocols shown in the lower levels. ◦ The lower layers of the stack are concerned with moving data over the network and providing services to the upper layers. ◦ While upper layers focused on the content of the message being 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 like Cisco, Huawei etc. ◦ A standards-based protocol suite that ensures interoperability Layers Protocols & their function Application Layer 1. DNS- Domain Name System, used to translates domain names such as cisco.com, into IP addresses. 2. DHCPv4 or DHCPv6 – Dynamic Host Configuration Protocol for IPv4 or IPv6, used to assign the IP Address automatically or dynamically. 3. SMTP - Simple Mail Transfer Protocol, used for sending the email 4. POP3 & IMAP- (Post Office Protocol & Internet Message Protocol) used to receive the email. 5. FTP- File Transfer Protocol – used to send or receive the files. 6. SFTP – Secured File Transfer (Encrypted) 7. TFTP – Trivial File Transfer – (less overhead than FTP) 8. HTTP- Hypertext transfer protocol, used for the communication between web client and web server. 9. HTTPs- Secured HTTP(Encrypted) Transport Layer 1. TCP – Transmission Control protocol, it is Connection oriented, reliable and acknowledges transmission. 2. UDP – User Datagram protocol, It is connectionless, unreliable, doesn’t acknowledge transmission. Internet Layer 1. IPv4 - Internet Protocol version 4. (32-bit Addressing) receives message segments from the transport layer, packages messages into packets, and addresses packets 2. IPv6 - IP version 6. Similar to IPv4 but uses a 128-bit address. 3. NAT - Network Address Translation. Translates IPv4 addresses from a private network into globally unique public IPv4 addresses. 4. ICMP – Internet Message Control Protocol, used to Provides feedback from a destination host to a source host about errors in packet delivery. 5. Routing Protocols – OSPF, EIGRP, BGP, used to find the best path for the transmission of the packet. Network Access Layer 1. ARP - Address Resolution Protocol. use to find the MAC Address from the given IP Address. 2. Ethernet – It defines the rules for wiring and signaling standards of the network access layer. 3. WLAN – It defines the rules for Wireless Local Area Network. 3.5 Reference Models 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 Reference Models: The OSI Reference Model OSI Model Description Layer 7 - Application Contains protocols used for process-to-process communications. 6- Provides for common representation of the data transferred between Presentation application layer services. Provides services to the presentation layer and to manage data 5 - Session exchange. Defines services to segment, transfer, and reassemble the data for 4 - Transport individual communications. Provides services to exchange the individual pieces of data over the 3 - Network network. 2 - Data Link Describes methods for exchanging data frames over a common media. Describes the means to activate, maintain, and de-activate physical 1 - Physical connections. Reference Models :The TCP/IP Reference Model This type of model closely matches the structure of a particular protocol suite. The TCP/IP model is a protocol model because it describes the functions that occur at each layer of protocols within the TCP/IP suite. TCP/IP is also used as a reference model. TCP/IP Model Description Layer Application Represents data to the user, plus encoding and dialog control. Supports communication between various devices across diverse Transport networks. Internet Determines the best path through the network. Network Controls the hardware devices and media that make up the network. Access 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. 3.6 Data Encapsulation 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. 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. Animation-3.6.1 Data Encapsulation : Protocol Data Units Encapsulation is the process of adding information to the data by protocol at each layer. The form that a piece of data takes at any layer is called a protocol data unit (PDU). During encapsulation, each succeeding layer encapsulates the PDU that it receives from the layer above in accordance with the protocol being used. 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, Here 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) Data Encapsulation : 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. Animation-3.6.4 Data Encapsulation :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) Animation-3.6.5 3.7 Data Access 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. Data Access :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. Data Access : Layer 3 Logical Address (Cont.) 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. Data Access IP 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 Data Access : 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 be the receiver and always be on the same link as the source. 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? Data Access Role of the Network Layer Addresses : Different IP Networks 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 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. Default Gateway Data Access Role of the Data Link Layer Addresses: Different IP Networks (Cont.) 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(Mac Address will change from link to link or hop to hop, the L3 addressing(IP Address) remains the same. Data Access : 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(Default Gateway) interface) receives frame Data Access :Data Link Addresses (Cont.) The MAC addressing for the second hop is: ◦ Source – (First Router- exit interface) sends frame ◦ Destination – (Second Router) receives frame Data Access :Data Link Addresses (Cont.) The MAC addressing for the last segment is: ◦ Source – (Second Router- exit interface) sends frame ◦ Destination – (Web Server NIC) receives frame Data Access : Data Link Addresses (Cont.) 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. Reference : ◦ www.netacad.com