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Chapter 20. Network Layer Protocols: ARP, IPv4, ICMPv4, IPv6, and ICMPv6

Chapter 20. Network Layer Protocols: ARP, IPv4, ICMPv4, IPv6, and ICMPv6. 20.1 ARP 20.2 IP 20.3 ICMP 20.4 IPv6. Protocols at network layer. In TCP/IP suite, five network layer protocols: ARP, RARP, IP, ICMP, and IGMP. Address Resolution Protocol (ARP).

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Chapter 20. Network Layer Protocols: ARP, IPv4, ICMPv4, IPv6, and ICMPv6

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  1. Chapter 20.Network Layer Protocols:ARP, IPv4, ICMPv4, IPv6, and ICMPv6 20.1 ARP 20.2 IP 20.3 ICMP 20.4 IPv6 Computer Networks

  2. Protocols at network layer • In TCP/IP suite, five network layer protocols: ARP, RARP, IP, ICMP, and IGMP Computer Networks

  3. Address Resolution Protocol (ARP) • Two levels of addresses: IP and MAC • Need to be able to map an IP address to its corresponding MAC address • Two types of mapping : static and dynamic • Static mapping has some limitations and overhead against network performance • Dynamic mapping: ARP and RARP • ARP: mapping IP address to a MAC address • RARP (replaced by DHCP): mapping a MAC address to an IP address Computer Networks

  4. ARP operation • ARP associates an IP address with its MAC addresses • An ARP request is broadcast; an ARP reply is unicast. Computer Networks

  5. ARP packet format • Protocol Type: 0800 for IPv4, Hardware length: 6 for Ethernet, Protocol length: 4 for IPv4 Computer Networks

  6. Encapsulation of ARP packet • ARP packet is encapsulated directly into a data link frame (example: Ethernet frame) Computer Networks

  7. ARP Operation • The sender knows the IP address of the target • IP asks ARP to create an ARP request message • The message is encapsulated in a frame (destination address = broadcast address) • Every host or router receives the frame. The target recognizes the IP address • The target replies with an ARP reply message (unicast with its physical address) • The sender receives the reply message knowing the physical address of the target • The IP datagram is now encapsulated in a frame and is unicast to the destination Computer Networks

  8. Four different cases using ARP Computer Networks

  9. Example Computer Networks

  10. Internet Protocol (IP) • IP: Host-to-host network layer delivery protocol • Unreliable and connectionless datagram protocol for a best-effort delivery service • The total length field defines the total length of the datagram including the header. Computer Networks

  11. IP Header • Version: IPv6, IPv4 • Differentiated services defines the class of the datagram for Quality if Servicre(QoS) • Total length = Length of data + header length : 65535 (216 – 1) • Identification, flag, and offset for fragmentation • Time to live (TTL): Used to control the max. number of hops (router) visited by the datagram • Protocol for Multiplexing: 1: ICMP, 2: IGMP, 6: TCP, 17: UDP, 89: OSPF Computer Networks

  12. Checksum Computer Networks

  13. Fragmentation • Ethernet and ATM : Fragmentation • Maximum Transfer Unit (MTU) : 65,535 bytes for IP datagram Computer Networks

  14. Field related to fragmentation • Identification: identifies a datagram originating form the source host • Flags: the first bit (reserved), the second bit (do not fragment bit), the third bit (more fragment bit, 0 means this is the last or only fragment) • Fragmentation offset: (13 bits cannot represent a sequence of bytes greater than 8191 Computer Networks

  15. ICMP • IP has no error-reporting or error-correcting mechanism • IP also lacks a mechanism for host and management queries • Internet Control Message Protocol (ICMP) is designed to compensate for two deficiencies, which is a companion to the IP • Two types messages: error-reporting messages and query messages Computer Networks

  16. Error-reporting messages • ICMP always reports error messages to the original source. • Source quench: There is no flow control or congestion control mechanism in IP. • Time exceed: (1) TTL related, (2) do not receive all fragments with a certain time limit • Redirection: To update the routing table of a host Computer Networks

  17. Query messages • To diagnose some network problems • A node sends a message that is answered in a specific format by the destination node • Echo for diagnosis; Time-stamp to determine RTT or synchronize the clocks in two machines; Address mask to know network address, subnet address, and host id; Router solicitation to know the address of routers connected and to know if they are alive and functioning Computer Networks

  18. IPv6 address • The use of address space is inefficient • Minimum delay strategies and reservation of resources are required to accommodate real-time audio and video transmission • No security mechanism (encryption and authentication) is provided • IPv6 (IPng: Internetworking Protocol, next generation) • Larger address space (128 bits) • Better header format • New options • Allowance for extention • Support for resource allocation: flow label to enable the source to request special handling of the packet • Support for more security Computer Networks

  19. IPv6 address CIDR address Computer Networks

  20. IPv6 datagram • IPv6 defines three types of addresses: unicast, anycast (a group of computers with the same prefix address), and multicast Computer Networks

  21. IPv6 Header • Version: IPv4, IPv6 • Priority (4 bits): the priority of the packet with respect to traffic congestion • Flow label (3 bytes): to provide special handling for a particular flow of data • Payload length • Next header (8 bits): to define the header that follows the base header in the datagram • Hop limit: TTL in IPv4 • Source address (16 bytes) and destination address (16 bytes): if source routing is used, the destination address field contains the address of the next router Computer Networks

  22. ICMPv6 • ICMPv4 has been modified to make it more suitable for IPv6 • ARP and IGMP in version 4 are combined in ICMPv6 and RARP dropped Computer Networks

  23. Three transition strategies from IPv4 to IPv6 • Transition should be smooth to prevent any problems between IPv4 and IPv6 systems Computer Networks

  24. Dual stack • All hosts have a dual stack of protocols before migrating completely to version 6 Computer Networks

  25. Tunneling • IPv6 packet is encapsulated in an IPv4 packet Computer Networks

  26. Header translation • Necessary when the majority of the Internet has moved to IPv6 but some systems still use IPv4 • Header format must be changed totally through header translation Computer Networks

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