1 / 24

Network Layer – Part 2

Network Layer – Part 2. 염익준. ICMP Features. Internet Control Message Protocol ICMP: Used by IP to send error and control messages ICMP uses IP to send its messages ICMP does not report errors on ICMP messages. ICMP Message Format. ICMP: Message Types. Type description

Download Presentation

Network Layer – Part 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Network Layer – Part2 염익준

  2. ICMP Features • Internet Control Message Protocol • ICMP: Used by IP to send error and control messages • ICMP uses IP to send its messages • ICMP does not report errors on ICMP messages.

  3. ICMP Message Format

  4. ICMP: Message Types • Typedescription • 0 echo reply (ping) • 3 destination unreachable • source quench • redirect • 8 echo request (ping) • 9 route advertisement • 10 router discovery • 11 TTL expired • bad IP header • timestamp request • timestamp reply • information request • information reply • address mask request • address mask reply

  5. Destination Unreachable

  6. IP version 6- IP Next Generation (IPng)

  7. Related RFCs

  8. IPng Considerations • Addressing • the two level structure of the IP address is convenient but wasteful of address spaces. • it is general practice to assign a unique network number to an IP network whether or not it is actually connected to the Internet. • networks are proliferating rapidly. • growth of TCP/IP usage in new areas will result in a rapid growth in the demand for unique IP addresses. • Performance • reduced number of fields in the IPv6 packet header • fixed length of header – extension header • disabling fragmentation

  9. IPng Considerations • Network service • should be possible to associate packets with particular services classes • flow label • Addressing flexibility • anycast – delivered to just one of a set of nodes • multicast – improved scalability by a scope filed • Security capabilities • providing authentication and privacy

  10. IPv6 Packet Header 0 4 12 16 24 31 V ersion T rafficClass FlowLabel PayloadLen NextHeader HopLimit SourceAddress DestinationAddress Next header/data

  11. Traffic Class • One bit for two classes • congestion controlled traffic • non-congestion controlled traffic • Three bits for eight priorities in each class

  12. Flow Label • a flow is a sequence of packets that • are generated from a single application instance from the source’s point of view • share attributes which affect how they are handled from the router’s point of view • Rules for flow label • hosts or routers that do not support the flow label field must • set the field to zero when originating a packet • pass the field unchanged when forwarding a packet • ignore the field when receiving a packet • all the packets with the same non-zero flow label must have the same destination address, source address, priority, hop-by-hop options header contents and routing header contents. • the source assigns a flow label to a flow.

  13. Addressing • 128 bit address space • Address notation: 47cd:1234:4422:ac02:0022:1234:a456:0123 3 m n o p 125 – m – n – o – p 010 RegistryID ProviderID SubscriberID SubnetID InterfaceID

  14. Address Prefix Assignment

  15. Anycast • Delivery method: • unicast: one-to-one • multicast: one-to-many • broadcast: one-to-all • anycast: one-to-one-of-many • Anycast address: an address assigned to multiple hosts

  16. Multicast Technology • Requires group communication • one-to-many or many-to-many • dynamic mgmt of group subscription • Big problem with unicast technology: bandwidth waste with multiple data flows

  17. Why Multicast? • Typical applications • Multimedia conference (video, audio, digital whiteboard) • Resource discovery (e.g., auto-topology) • War simulation • Commercial apps (e.g., transactions, news distribution) • Routing protocols (e.g., both EIGRP and OSPF use multicast to send updates to neighbors) • Games (e.g., distributed arcades) • Physics apps

  18. Principles of Multicasting • Special IP addresses are used to identify multicast groups • Hosts notify multicast routers about the multicast groups to which they (want to) belong • Multicast groups are managed by the routers using multicast routing protocols

  19. Multicast Addresses • Multicast packets are identified by Class D IP addresses • Global range from 224.0.0.0 to 239.255.255.255 • Reserved: 224.0.0.0-224.0.0.255 • Internet-wide addresses: 224.0.1.0-238.255.255.255 • Local addresses: 239.0.0.0-239.255.255.255 • Some special addresses • 224.0.0.1: all multicast systems on a subnet • 224.0.0.2: all multicast routers on a subnet

  20. Multicast Groups • IGMP - Internet Group Management Protocol (RFC 1112) • defines how hosts tell routers which groups they are part of; available on Unix, PCs, Mac • routers query directly connected hosts sending an IGMP query to 224.0.0.1 (i.e., all multicast systems) • when there is more than one multicast router on a LAN, only one has to send the query • access lists can be applied to restrict the multicast groups hosts can receive • hosts send a single reply per group per LAN

  21. Multicast Routing Protocols • Forwarding decisions: different from unicast protocols • multicast protocols use the source address instead of the destination address to make their forwarding decisions • Two main protocols • DVMRP (Distance Vector Multicast Routing Protocol) • Distance vector (RIP-like) algorithm • Static configuration based on tunnels between DVMRP routers (often Sun workstations) • Not easily scalable (e.g., max hops < 32) • PIM (Protocol Independent Multicast) • Typically installed on routers • Independent from the unicast routing protocols used by the router • Scalable (Dense-mode & Sparse-mode)

  22. Flooding • When a router receives a packet that is addressed to a multicast group, it determines whether this is the first time the router has seen this particular packet. • If so, it forwards the packet on all the interfaces except the one on which it arrived. • Simple to implement. • Does not scale well because of the large number of duplicate messages.

  23. RPF • Reverse Path Forwarding (RPF) • A router accepts a multicast packet from a source if and only if the packet has been received over the interface used to send unicast packets to the source • If the RPF test succeeds, the packet is forwarded to all the interfaces included in the router’s OIF (Outgoing Interface List) • If the RPF test fails, the multicast packet is discarded • A packet should never be re-sent over the RPF interface (to avoid loops)

  24. DVMRP • DVMRP constructs source-rooted multicast delivery trees using RPF algorithm. • Basic operations follow:. • The first datagram for any (source, group) pair is forwarded across the entire internetwork. • The leaf routers transmit prune messages back toward the source if there are no group members on their directly attached leaf subnetworks. • Periodically the prune state times out, and the next datagram for the (source, group) pair is forwarded across the entire internetworks. • Implements a “graft” operation for quickly establishing a new branch. • if a router that previously sent a prune message for a (source, group) pair discovers new group members on a leaf network, it sends a “graft message” to the group’s previous-hop router. • When an upstream router receives a “graft” message, it cancels the previously received prune message. Graft messages may cascade back towards the source to establish the branch to the multicast tree.

More Related