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CCNA TCP/IP

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Transcript

  • 1. CCNA Guide to Cisco Networking Fundamentals Chapter 3 TCP/IP
  • 2. Objectives
    • Discuss the origins of TCP/IP
    • Identify and discuss the different layer functions of TCP/IP
    • Describe the functions performed by protocols in the TCP/IP protocol suite, including ICMP, UDP, TCP, ARP, and RARP
    CCNA Guide to Cisco Networking Fundamentals
  • 3. Objectives (continued)
    • Use Ping and Trace and describe their functions
    • Explain how packets are transmitted
    • Describe the Cisco three-layer hierarchical model
    CCNA Guide to Cisco Networking Fundamentals
  • 4. Origins of TCP/IP
    • Transmission Control Protocol/Internet Protocol (TCP/IP)
      • Resulted from a coordinated effort by the U.S. Department of Defense (DOD)
    • Advanced Research Projects Agency (ARPA)
      • Charged with creating a wide area network (WAN)
      • Results were TCP/IP and ARPANET
    • DOD funded two projects
      • The adaptation of TCP/IP to work with UNIX
      • The inclusion of the TCP/IP protocol with Berkeley UNIX (BSD UNIX)
    CCNA Guide to Cisco Networking Fundamentals
  • 5. Overview of the TCP/IP Protocol Suite
    • The TCP/IP model explains how the protocol suite works to provide communications
      • Four layers: Application, Transport, Internetwork, and Network Interface
    • Requests for Comments (RFCs)
      • Define, describe, and standardize the implementation and configuration of the TCP/IP protocol suite
    CCNA Guide to Cisco Networking Fundamentals
  • 6. CCNA Guide to Cisco Networking Fundamentals
  • 7. Application Layer
    • Protocols at the TCP/IP Application layer include:
      • File Transfer Protocol (FTP)
      • Trivial File Transfer Protocol (TFTP)
      • Network File System (NFS)
      • Simple Mail Transfer Protocol (SMTP)
      • Terminal emulation protocol (telnet)
      • Remote login application (rlogin)
      • Simple Network Management Protocol (SNMP)
      • Domain Name System (DNS)
      • Hypertext Transfer Protocol (HTTP)
    CCNA Guide to Cisco Networking Fundamentals
  • 8. Transport Layer
    • Performs end-to-end packet delivery, reliability, and flow control
    • Protocols:
      • TCP provides reliable, connection-oriented communications between two hosts
        • Requires more network overhead
      • UDP provides connectionless datagram services between two hosts
        • Faster but less reliable
        • Reliability is left to the Application layer
    CCNA Guide to Cisco Networking Fundamentals
  • 9. Transport Layer (continued)
    • Ports
      • TCP and UDP use port numbers for communications between hosts
      • Port numbers are divided into three ranges:
        • Well Known Ports are those from 1 through 1,023
        • Registered Ports are those from 1,024 through 49,151
        • Dynamic/Private Ports are those from 49,152 through 65,535
    CCNA Guide to Cisco Networking Fundamentals
  • 10. CCNA Guide to Cisco Networking Fundamentals
  • 11. Transport Layer (continued)
    • TCP three-way handshake
      • Establishes a reliable connection between two points
      • TCP transmits three packets before the actual data transfer occurs
      • Before two computers can communicate over TCP, they must synchronize their initial sequence numbers (ISN)
      • A reset packet (RST) indicates that a TCP connection is to be terminated without further interaction
    CCNA Guide to Cisco Networking Fundamentals
  • 12. CCNA Guide to Cisco Networking Fundamentals
  • 13. CCNA Guide to Cisco Networking Fundamentals
  • 14. CCNA Guide to Cisco Networking Fundamentals
  • 15. Transport Layer (continued)
    • TCP sliding windows
      • Control the flow and efficiency of communication
      • Also known as windowing
        • A method of controlling packet flow between hosts
        • Allows multiple packets to be sent and affirmed with a single acknowledgment packet
      • The size of the TCP window determines the number of acknowledgments sent for a given data transfer
      • Networks that perform large data transfers should use large window sizes
    CCNA Guide to Cisco Networking Fundamentals
  • 16. Transport Layer (continued)
    • TCP sliding windows (continued)
      • Other flow control methods include
        • Buffering
        • Congestion avoidance
    CCNA Guide to Cisco Networking Fundamentals
  • 17. Internetwork Layer
    • Four main protocols function at this layer
      • Internet Protocol (IP)
      • Internet Control Message Protocol (ICMP)
      • Address Resolution Protocol (ARP)
      • Reverse Address Resolution Protocol (RARP)
    • ARP
      • A routed protocol
      • Maps IP addresses to MAC addresses
      • ARP tables contain the MAC and IP addresses of other devices on the network
    CCNA Guide to Cisco Networking Fundamentals
  • 18. Internetwork Layer (continued)
    • ARP (continued)
      • When a computer transmits a frame to a destination on the local network
        • It checks the ARP cache for an IP to MAC address mapping for the destination node
    • ARP request
      • If a source computer cannot locate an IP to MAC address mapping in its ARP table
        • It must obtain the correct mapping
    CCNA Guide to Cisco Networking Fundamentals
  • 19. Internetwork Layer (continued) CCNA Guide to Cisco Networking Fundamentals
  • 20. Internetwork Layer (continued)
    • ARP request (continued)
      • A source computer broadcasts an ARP request to all hosts on the local segment
        • Host with the matching IP address responds this request
    • ARP request frame
      • See Figure 3-7
    • ARP cache life
      • Source checks its local ARP cache prior to sending packets on the local network
    CCNA Guide to Cisco Networking Fundamentals
  • 21. Internetwork Layer (continued) CCNA Guide to Cisco Networking Fundamentals
  • 22. Internetwork Layer (continued)
    • ARP cache life (continued)
      • Important that the mappings are correct
      • Network devices place a timer on ARP entries
      • ARP tables reduce network traffic
    • Reverse Address Resolution Protocol (RARP)
      • Similar to ARP
      • Used primarily by diskless workstations
        • Which have MAC addresses burned into their network cards but no IP addresses
      • Client’s IP configuration is stored on a RARP server
    CCNA Guide to Cisco Networking Fundamentals
  • 23. Internetwork Layer (continued)
    • RARP request frame
      • See Figure 3-8
    • RARP client
      • Once a RARP client receives a RARP reply, it configures its IP networking components
        • By copying its IP address configuration information into its local RAM
    • ARP and RARP compared
      • ARP is concerned with obtaining the MAC address of other clients
      • RARP obtains the IP address of the local host
    CCNA Guide to Cisco Networking Fundamentals
  • 24. CCNA Guide to Cisco Networking Fundamentals
  • 25. Internetwork Layer (continued)
    • ARP and RARP compared (continued)
      • The local host maintains the ARP table
      • A RARP server maintains the RARP table
      • The local host uses an ARP reply to update its ARP table and to send frames to the destination
      • The RARP reply is used to configure the IP protocol on the local host
    • Routers and ARP
      • ARP requests use broadcasts
      • Routers filter broadcast traffic
      • Source must forward the frame to the router
    CCNA Guide to Cisco Networking Fundamentals
  • 26. Internetwork Layer (continued)
    • ARP tables
      • Routers maintain ARP tables to assist in transmitting frames from one network to another
      • A router uses ARP just as other hosts use ARP
      • Routers have multiple network interfaces and therefore also include the port numbers of their NICs in the ARP table
    • The Ping utility
      • Packet Internet Groper (Ping) utility verifies connectivity between two points
      • Uses ICMP echo request/reply messages
    CCNA Guide to Cisco Networking Fundamentals
  • 27. Internetwork Layer (continued) CCNA Guide to Cisco Networking Fundamentals
  • 28. Internetwork Layer (continued) CCNA Guide to Cisco Networking Fundamentals
  • 29. Internetwork Layer (continued)
    • The Trace utility
      • Uses ICMP echo request/reply messages
      • Can verify Internetwork layer (OSI-Network layer) connectivity
      • Shows the exact path a packet takes from the source to the destination
        • Accomplished through the use of the time-to-live (TTL) counter
      • Several different malicious network attacks have also been created using ICMP messages
        • Example: ICMP flood
    CCNA Guide to Cisco Networking Fundamentals
  • 30. Internetwork Layer (continued) CCNA Guide to Cisco Networking Fundamentals
  • 31. Network Interface Layer
    • Plays the same role as the Data Link and Physical layers of the OSI model
    • The MAC address, network card drivers, and specific interfaces for the network card function at this level
    • No specific IP functions exist at this layer
      • Because the layer’s focus is on communication with the network card and other networking hardware
    CCNA Guide to Cisco Networking Fundamentals
  • 32. Understanding Frame Transmission
    • Each host on a segment evaluates the frame
      • To determine whether the listed destination MAC address matches its own or is a broadcast to all hosts
    • The host makes a copy of the frame and sends the original along the network path
    • On the destination host, frames are sent up the TCP/IP stack
      • Removing each layer header information
    • For a packet to be routed on a TCP/IP internetwork
      • An IP address and MAC address are required for both the source and destination hosts
    CCNA Guide to Cisco Networking Fundamentals
  • 33. Routers on the Network
    • A router requires:
      • An IP address for every network segment to which it is connected
      • A separate network interface or port for each network segment
    • Computers send frames to destinations that are not on their segment to the router (default gateway)
    • The router must determine which subnet should receive the frame
      • The router references its routing table
    CCNA Guide to Cisco Networking Fundamentals
  • 34. Routers on the Network (continued) CCNA Guide to Cisco Networking Fundamentals
  • 35. Network to Network
    • Routers maintain routing tables that they use to route packets from one network to another
    • When a network uses TCP/IP, each port on a router requires an IP address
      • Allows the router to correctly forward the packet to the appropriate network segment
    • On a TCP/IP network, the logical addresses on a certain segment must be matched
      • If you move a computer from one segment to another, the IP address will have to be changed
    CCNA Guide to Cisco Networking Fundamentals
  • 36. Network to Network (continued) CCNA Guide to Cisco Networking Fundamentals
  • 37. Dynamic or Static Tables
    • Routing tables match network addresses with the addresses of the routers that handle those networks
      • The tables can be built statically or dynamically
    • Dynamic updates are provided through routing protocols
      • A router capable of dynamic routing can choose from among the various routes on a network
      • The router communicates with other dynamic routers
        • To determine the most efficient route from one point to another on the network
    CCNA Guide to Cisco Networking Fundamentals
  • 38. Dynamic or Static Tables (continued)
    • Methods to determine the best path across a network
      • The distance-vector algorithm
      • The link-state algorithm
    CCNA Guide to Cisco Networking Fundamentals
  • 39. Transmitting Packets to Remote Segments
    • When TCP/IP hosts transmit packets to remote segments
      • They contact their default gateway (usually a router)
    • The router checks its routing tables against the destination IP address
      • To locate the appropriate network interface through which to forward the packet
    • Router re-addresses the frame or sends the packet to the next router in the path (indirect routing)
    CCNA Guide to Cisco Networking Fundamentals
  • 40. Routing Packets CCNA Guide to Cisco Networking Fundamentals
  • 41. Routing Packets (continued) CCNA Guide to Cisco Networking Fundamentals
  • 42. Routing Packets (continued) CCNA Guide to Cisco Networking Fundamentals
  • 43. Routing Packets (continued) CCNA Guide to Cisco Networking Fundamentals
  • 44. The Cisco Three-Layer Hierarchical Model
    • Cisco Three-Layer Hierarchical model
      • Does not describe how communications take place
      • Focuses on how best to design a network
        • Especially a relatively large network or one that is expected to grow
    • Each layer of the model is involved in specific functions
      • Is typically defined by a particular type of device
    • The three layers of the model from bottom up are Access, Distribution, and Core
    CCNA Guide to Cisco Networking Fundamentals
  • 45. CCNA Guide to Cisco Networking Fundamentals
  • 46. Access Layer
    • The layer closest to the users, where they attach to the network
    • Could be a router if the network is very small
      • But typically a hub or layer 2 switch
    • Sometimes called the desktop layer because it deals with connecting workstations to the network
    • Frames are delivered to the users at this layer
    CCNA Guide to Cisco Networking Fundamentals
  • 47. Distribution Layer
    • Separates the Access layer from the Core layer
    • Implements network policies, and provides many networking services
      • Such as Network Address Translation (NAT), firewall protection, and quality of service (QoS)
    • IP addressing hierarchy is managed at this layer
      • IP addressing is the process of assigning unique IP addresses to devices on the network
    • Typically involves routers and includes all of the router functions
      • Provides almost all of the connectivity tasks
    CCNA Guide to Cisco Networking Fundamentals
  • 48. Core Layer
    • Responsible for switching large amounts of data quickly and efficiently
    • To prevent slowing down the switching process:
      • This layer should not be burdened with security or traffic control measures or any unnecessary additional equipment
    • The primary device at this layer is a high-end layer 3 switch
      • Essentially the backbone of the network
    CCNA Guide to Cisco Networking Fundamentals
  • 49. Summary
    • TCP/IP is not limited to transmission control and Internet protocols
    • TCP/IP was started by the Defense Advanced Research Projects Agency (DARPA)
    • TCP/IP maps to a four-layer network model: Application, Transport, Internetwork, and Network Interface
    • The Application layer in the TCP/IP model covers the Application, Presentation, and Session layers of the OSI reference model
    CCNA Guide to Cisco Networking Fundamentals
  • 50. Summary (continued)
    • The TCP and UDP protocols reside at the Transport layer of the TCP/IP networking model
    • Both TCP and UDP use port numbers from 1 to 65,535 to establish their communications between two points
    • The Internet Protocol (IP) resides at the Internetwork layer and provides the logical address that can be passed through a router
    • You can use the Ping utility with IP and ICMP to diagnose and troubleshoot network connections
    CCNA Guide to Cisco Networking Fundamentals
  • 51. Summary (continued)
    • Address Resolution Protocol (ARP) and Reverse ARP (RARP) reside in the Internetwork layer
    • The MAC address is the final leg of communication between hosts
    • Routing tables can be created manually and dynamically
    • Cisco developed the Three-Layer Hierarchical model to help network administrators design more efficient networks
    CCNA Guide to Cisco Networking Fundamentals

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