Chapter 3: Network Protocols and Communications CCENT Routing and Switching Introduction to Networks v6.0 Instructor Planning Guide CCNET v6 1
Chapter 3: Network Protocols and Communications CCENT Routing and Switching Introduction to Networks v6.0 CCNET v6 12
Chapter 3 - Sections & Objectives 3.1 Rules of Communication Describe the types of rules that are necessary to successfully communicate. 3.2 Network Protocols and Standards Explain why protocols are necessary in communication. Explain the purpose of adhering to a protocol suite. Explain the role of standards organizations in establishing protocols for network interoperability. Explain how the TCP/IP model and the OSI model are used to facilitate standardization in the communication process. 3.3 Data Transfer in the Network Explain how data encapsulation allows data to be transported across the network. Explain how local hosts access local resources on a network. CCENT v6 13
3.1 RULES OF COMMUNICATION CCENT v6 14
Rules of Communication Rules or protocols govern all methods of communication Protocols are necessary for effective communication All communication methods have elements in common: Identify sender or source Identify receiver or destination Identify channel or media Common language and grammar Speed and timing of delivery Confirmation or acknowledgment requirements CCENT v6 15
Rules of Communication Protocols used in network communications also define: Message Encoding process of converting information into another acceptable form Message Formatting and Encapsulation used to place one message inside another message for transfer from the source to the destination Message Size process of breaking up a long message into individual pieces Message Timing process of knowing when a message begins, how must can be received at a time, and how to respond back Message Delivery Options who will receive the message and how will it be received CCENT v6 16
Message Encoding Encoding between hosts must be in appropriate format for the medium Messages are first converted into bits by the sending host Each bit is encoded into a pattern of sounds, light waves, or electrical impulses depending on the network media The destination host receives and decodes the signals in order to interpret the message CCENT v6 17
Message Formatting and Encapsulation There is an agreed format for letters and addressing letters which is required for proper delivery Putting the letter into the addressed envelope is called encapsulation Each computer message is encapsulated in a specific format, called a frame, before it is sent over the network A frame acts like an envelope providing destination address and source address CCENT v6 18
Message Size Humans break long messages into smaller parts or sentences The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements Long messages must also be broken into smaller pieces to travel across a network A receiving host will reconstruct multiple frames Each segment is encapsulated in a separate frame with the address information, and is sent over the network At the receiving host, the messages are de-encapsulated and put back together into the original message to be processed and interpreted CCENT v6 19
Message Timing Access Method Hosts on a network need to know when to begin sending messages and how to respond when collisions occur Flow Control Used by source and destination hosts to negotiate correct timing to avoid overwhelming the destination and ensure that packets are not dropped because too much data is being sent too quickly Response Timeout Hosts on the network have rules that specify how long to wait for responses and what action to take if a response timeout occurs CCENT v6 20
Message Delivery Options IPv4: Unicast Message Multicast Message Broadcast Message One-to-one delivery One-to-many delivery IPv6: Unicast One-to-One Multicast One-to-Many Anycast One-to-Nearest One-to-all delivery CCENT v6 21
3.2 NETWORK PROTOCOLS AND STANDARDS CCENT v6 22
Network Protocols and Standards Rules that Govern Communications May be specified by a standards organization or developed by a vendor Role of network protocols: Define a common format and set of rules for exchanging messages between devices Define how messages are exchanged between the source and the destination How the message is formatted or structured The process by which networking devices share information about pathways with other networks How and when error and system messages are passed between devices The setup and termination of data transfer sessions Protocol Interaction Example: web server and client CCENT v6 23
Protocol Suites Protocol Suites and Industry Standards Sets of rules that work together to help solve a problem TCP/IP is an open standardi Implemented by hosts and networking devices in software, hardware or both Viewed in terms of layers, with each higher-level service depending on the functionality defined by the protocols shown in the lower levels TCP/IP Protocol Suites The TCP/IP protocol suite is an open standard, the protocols are freely available, and any vendor is able to implement these protocols on their hardware or in their software Can you name some of the protocols from the TCP/IP protocol suite? Know the protocols and the layer they operate in CCENT v6 24
Development of TCP/IP Advanced Research Projects Agency Network (ARPANET) was the predecessor to today s Internet ARPANET was funded by the U.S. Department of Defense for use by universities and research laboratories CCENT v6 25
Interaction of TCP/IP Model Protocols Communication between a web server and web client is an example of an interaction between several protocols: Application Layer Hypertext Transfer Protocol (HTTP) Defines the content and formatting of the requests and responses that are exchanged between the client and server. Presentation Layer Hypertext Markup Language (HTML) Defines the syntax both sides of the communication must understand in order to communicate. Transport Layer Transmission Control Protocol (TCP) is responsible for controlling the size and rate of the HTTP messages exchanged between server and client. It segments the messages and manages the segments in the individual conversation between the host and destination. Internet Layer Internet Protocol (IP) or logical address is a unique host address for data communications at the internet layer Network Access Layer Describes two primary functions: 1) communication over a data link and 2) the physical transmission of data on the network media: - Data-link management protocols take the packets from IP and format them to be transmitted over the media. - Physical media standards and protocols govern how the signals are sent and how they are interpreted by the receiving clients CCENT v6 26
TCP/IP Communication Process From the user perspective, what is the correct order of the protocol stack that is used to prepare a web request for transmission? HTTP (7) Identifies the type of page that will be rendered HTML (6) Prepares the Hypertext Markup Language (HTML) page TCP (4) Breaks the data into segments and identifies each IP (3) The IP source and destination addresses are added, creating an IP Packet Ethernet (2) The Ethernet information is added creating the Ethernet Frame - This frame is delivered to the nearest router along the path towards the web client - Each router adds new data link information before forwarding the packet CCENT v6 27
TCP/IP Communication Process (Cont.) When receiving the data link frames from the web server, the client processes and removes each protocol header in the opposite order it was added: First the Ethernet header is removed Then the IP header Then the Transport layer header Finally the HTTP information is processed and sent to the client s web browser CCENT v6 28
Network Protocols Address Resolution Protocol (ARP) used to discover the MAC address of any host on the local network Reverse ARP Used to find the IP address of the local machine Proprietary protocols are developed by organizations who have control over their definition and operation Advantages of using standards to develop and implement protocols: Products from different manufacturers can interoperate successfully A host and a server running different operating systems can successfully exchange data CCENT v6 29
Standards Organizations: ISOC, IAB, and IETF Internet Society (ISOC) Responsible for promoting open development of standards and protocols, evolution, and Internet use throughout the world Internet Architecture Board (IAB) management and development of Internet standards Internet Engineering Task Force (IETF) develops, updates, and maintains Internet and TCP/IP technologies CCENT v6 30
Standards Organizations: Institute of Electrical and Electronics Engineers (IEEE) Provides educational and career enhancement opportunities to promote the skills and knowledge with the electronics industry Creates and maintains standards affecting a wide range of industries including power and energy, healthcare, telecommunications, and networking Important to us: IEEE 802.3 CSMA/CD or Ethernet IEEE 802.11 CSMA/CA or Wireless CCENT v6 31
Other Standards Organization The Telecommunications Industry Association (TIA) responsible for developing communication standards in a variety of areas including radio equipment, cellular towers, Voice over IP (VoIP) devices, satellite communications, and more. Many of their standards are produced in collaboration with the EIA The Electronic Industries Alliance (EIA) Best known for its standards related to electrical wiring, connectors, and the 19-inch racks used to mount networking equipment The International Telecommunications Union Telecommunications Standardization Sector (ITU-T) defines standards for video compression, Internet Protocol Television (IPTV), and broadband communications, such as a digital subscriber line (DSL) Internet Research Task Force (IRTF) - focused on long-term research related to Internet and TCP/IP protocols The Internet Corporation for Assigned Names and Numbers (ICANN) Coordinates IP address allocation, the management of domain names used by DNS, and the protocol identifiers or port numbers used by TCP and UDP protocols The Internet Assigned Numbers Authority (IANA) Responsible for overseeing and managing IP address allocation, domain name management, and protocol identifiers CCENT v6 32
Open Standards Encourage interoperability, competition, and innovation Standards organizations are usually vendor-neutral, non-profit organizations established to develop and promote the concept of open standards CCENT v6 33
The Benefits of Using a Layered Model An advantage of network devices using open standard protocols: A host and a server running different operating systems can successfully exchange data Fosters competition among device and software vendors by enforcing the compatibility of their products Assisting in protocol design since protocols at each layer have defined functions Preventing technology changes in one layer from affecting other layers Providing a common language to describe networking functions and capabilities CCENT v6 34
International Organization for Standards (ISO) The world s largest developer of international standards for a wide variety of products and services Best known for its Open Systems Interconnection (OSI) reference model CCENT v6 35
OSI Reference Model Layer 7 The Application layer provides the means for end-to-end connectivity between individuals in the human network using data networks. Layer 6 The Presentation layer provides for common representation of the data transferred between application layer services. Layer 5 The Session layer provides services to the presentation layer to organize its dialogue and to manage data exchange. Layer 4 The Transport layer defines services to segment, transfer, and reassemble the data for individual communications between the end devices. It describes the ordered and reliable delivery of data between source and destination. Layer 3 The Network layer provides services to exchange the individual pieces of data over the network between identified end devices. IP or Logical addressing. Layer 2 The Data Link layer protocols describe methods for exchanging data frames between devices over a common media. MAC or physical addressing. Layer 1 The Physical layer protocols describe the mechanical, electrical, functional, and procedural means to activate, maintain, and de-activate physical-connections for bit transmission to and from a network device. CCENT v6 36
The TCP/IP Protocol Model The TCP/IP Protocol Model Created in the early 1970s for internetwork communications Open Standard Also called The TCP/IP Model or the Internet Model CCENT v6 37
Comparing the OSI and TCP/IP Models Relationship between layers: The TCP/IP Application layer combines layers 5-7 of the OSI model The TCP/IP Transport layer and OSI Transport layer provide similar services and functions The TCP/IP Network layer and OSI Internet layer provide similar services and functions The TCP/IP Network Access layer combines layers 1-2 of the OSI model If a host were to transfer a file to a server, what layers of the TCP/IP model would be used? All four layers CCENT v6 38
3.3 DATA TRANSFER IN THE NETWORK CCENT v6 39
Message Segmentation Large streams of data are divided into smaller, more manageable pieces to send over the network Advantages: Segmentation Break communication into pieces Multiplexng Different conversations can be interleaved Increased reliability of network communications - Each piece must be labeled - If part of the message fails to make it to the destination, only the missing pieces need to be retransmitted Disadvantage: Increased level of complexity CCENT v6 40
Protocol Data Units (PDUs) Encapsulation process As application data is passed down the protocol stack, information is added at each level General term used to describe a piece of data at any layer of a networking model Encapsulation/De-Encapsulation Process placing one message format inside another: Data Segments sent from the transport layer to the internet layer Packets Logical addresses are encapsulated Frames Bits received from the network medium by the NIC of a host Bits Describe the addressing that will be generated by a host in the encapsulation process: A frame with the source and destination MAC address A packet with the source and destination IP address CCENT v6 41
Encapsulation Example The encapsulation process works from top to bottom: Data is divided into segments The TCP or UDP segment is encapsulated in the IP Packet The IP packet is encapsulated in the Ethernet Frame Ethernet frame is turn into bits CCENT v6 42
De-encapsulation De-encapsulation is the process used by a receiving device to remove one or more of the protocol headers The de-encapsulation process works from bottom to top: Bits are turned into digital information and passed to the Data Link layer Frame information is read and striped off before sending to the Network layer Packet information is read and striped off before send to the Transport layer Segment is read, sequencing is applied, and the data is reorder CCENT v6 43
Data Transfer in the Network Network Addresses (Logical Address) Source IP address The IP address of the sending device, the original source of the packet Destination IP address The IP address of the receiving device, the final destination of the packet Deliver the IP packet from the original source to the final destination, either on the same network or to a remote network. Data Link Addresses (Physical Address) Source MAC address Destination MAC address As the IP packet travels from source to destination it is encapsulated in a new data link frame when it is forwarded by each router What will happen if the default gateway address is incorrectly configured on a host? The host cannot communicate with hosts in other networks CCENT v6 44
Communicating with Device / Same Network The network layer addresses, or IP addresses, indicate the original source and final destination. Network portion The left-most part of the address indicates which network the IP address is a member of. Host portion The remaining part of the address identifies a specific device on the network. The data link frame which uses MAC addressing, is sent directly to the receiving device. Source MAC address - address of sending device. Destination MAC address address of receiving device. What address does a NIC use when deciding whether to accept a frame? Destination MAC PC 1 192.168.1.110 AA-AA-AA-AA- AA-AA ARP Request PC 2 192.168.1.111 BB-BB-BB-BB- BB-BB R1 192.168.1.1 11-11-11-11-11-11 FTP Server 192.168.1.9 CC-CC-CC-CC- CC-CC R2 172.16.1.99 22-22-22-22-22-22 Web Server 172.16.1.99 AB-CD-EF- 12-34-56 CCENT v6 45
Communicating with Device / Different Network The source and destination IP addresses represent hosts on different networks The data link frame cannot be sent directly to the remote destination host, therefore the frame is sent to the default gateway (nearest router interface) A default gateway is the logical address of the router interface on the same network as the host computer The router removes the received Layer 2 information and adds new data link information before forwarding out the exit interface Which protocol is used by a computer to find the MAC address of the default gateway? ARP PC 1 192.168.1.110 AA-AA-AA- AA-AA-AA PC 2 192.168.1.111 BB-BB-BB- BB-BB-BB R1 192.168.1.1 11-11-11-11-11-11 FTP Server 192.168.1.9 CC-CC-CC- CC-CC-CC R2 172.16.1.1 22-22-22-22-22-22 Web Server 172.16.1.99 AB-CD-EF- 12-34-56 CCENT v6 46 ARP Requ est
Using Wireshark to View Network Traffic CCENT v6 47
CHAPTER TERMS CCENT v6 48
Section 3.1 New Terms and Commands access method acknowledgement broadcast decoder encapsulation encoder flow control message message delivery options message encoding message formatting message formatting and encapsulation message size message timing multicast protocols receiver response timeout segmenting transmission medium transmitter unacknowledged unicast CCENT v6 49
Section 3.2 New Terms and Commands Advanced Research Projects Agency Network (ARPANET) AppleTalk application protocol Electronic Industries Alliance (EIA) Hypertext Markup Language (HTML) IEEE 802.3 IEEE 802.11 Institute of Electrical and Electronics Engineers (IEEE) International Corporation for Assigned Names and Numbers (ICANN) International Telecommunications Union- Telecommunication Standardization Sector (ITU- T) Internet Architecture Board (IAB) Internet Assigned Numbers Authority (IANA) Internet Engineering Task Force (IETF) internet protocol Internet Society (ISOC) Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) Media Access Control (MAC) network access protocols network protocol suite protocol model protocol stack proprietary protocol reference model Request for Comments (RFC) standards organization standards-based protocol Telecommunications Industry Association (TIA) Transmission Control Protocol/IP (TCP/IP) transport protocol CCENT v6 50
Section 3.3 New Terms and Commands Address Resolution Protocol (ARP) bits data data encapsulation data link address de-encapsulation default gateway destination data link address destination IP address frame Multiplexing network address packet protocol data unit (PDU) source IP address source data link address Segment segmentation CCENT v6 51
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