Presentation OverviewInternet ProtocolsIP AddressingIP Addressing (cont’d)IP Addressing Drawbacks and SolutionsIP ProtocolNetwork Topology RevisitedRouting protocolsOvercoming the Problem of the Internet GrowthIP version 6IP version 6 (cont’d)Mobility and IPMobileIPMobileIP (cont’d)TCP and UDPUDPTCPTCP Reliability MechanismsTCP (cont’d)WAPWhy is WAP needed?Bearer LimitationsWAP Forum: www.wapforum.orgHow does WAP work?What works with WAP?WAP Protocol Model (Stack)WAP ArchitectureWDP LayerWTLS LayerWTP LayerWSP LayerWAEWMLBenefits of WAPDrawbacks to WAPCaches and proxy serversDNSThe Internet Naming SchemeDNS OperationDNS and cachingInternet and Network SecurityInternet and Network Security (cont’d)How to Defend?Example ScenarioBut,FirewallFiltering levelsFiltering levels (cont’d)Basic Internet FirewallsAdvanced Internet FirewallsAdvanced Internet Firewalls (cont’d)Virtual Private NetworksDirectory and Discovery ServicesJiniJini Directory-Related ComponentJini Directory-Related Component (cont’d)Slide 581Yelena YeshaOlga StreltchenkoWAP slides by Anupam JoshiNetworking Technologies2Presentation OverviewInternet ProtocolsWAPCaching and ProxiesDNSFirewallsDirectory and Discovery Services3Internet ProtocolsOriginally developed to support simple wide-area applications (ftp, e-mail).Scaled up very well to support more sophisticated distributed applications.Standardization of TCP/IP.Exceptions:WAP for wireless applications on portable devices;Special protocols to support MM streaming applications.4IP AddressingScheme for addressing and routing IP packets.1978-82 TCP/IP standardization provided for 232 or approximately 4 billion hosts.The Internet growth outstripped the predictions.The address space allocation has been inefficient.IP address=network identifier+host identifier Written asClasses: A, B, C, D and E.D is reserved for multicast communication, E –for future uses.5IP Addressing (cont’d)A: 224 hosts on each subnet, national wide area networksB: more than 255 computers on a subnet, big companies.C: other network operators101011011101111Network ID, 7bitsClass AClass BNetwork ID, 14 bitsNetwork ID, 21 bitsHost ID, 24 bitsHost ID, 16 bitsHost ID, 8 bitsMulticastunused Class CClass D Class E6IP Addressing Drawbacks and SolutionsDrawbacks:If a computer is connected to more than one network it needs more than one IP address.Organizations cannot reliably predict their growth and tend to over-budget;Outcome: exhaustion of class B addresses.IP address is susceptible to IP spoofing, or counterfeiting of the source address in the IP header.Denial-of-service attacks by placing the destination IP address in the target address field (remember Feb 2000?). Solutions:Aggressive: IPv6 with its 128-bit address fields;Use of mask fields and CIDR (classless inter-domain routing).7IP ProtocolProvides an unreliable or best-effort delivery serviceOnly checksum is the header checksum.IP layer Puts IP datagrams into network packets suitable for transmission in the underlying network;E.g., Ethernet.When the datagram is longer than MTU of the underlying network, it is broken into smaller segments and reassembled at the destination.Must insert “physical” network address of the message destination if necessary;Depends on the underlying network technology, i.e., Ethernet requires and Ethernet address for the host on the local Ethernet.8Network Topology RevisitedThe Internet BackboneSuper-high-bandwidth link between smaller networks like intranets;consists of multiple networks operated by multiple companies, like UUnet, AT&T, SprintLink, Quest, etc.;These networks come together at various peering points.Autonomous system (AS): conceptual partition of the topological map of the internet.Subdivide into areas;Example: intranets of big organizations.9Routing protocolsRIP1: distance-vector algorithm.Convergence problems.RIP2: amendment of of RIP1 to accommodate CIDR and authentication of IP packets, improve multicast routing.OSPF: open-shortest-path-first.Better convergence than the one exhibited by RIP.Incremental adoption of better routing algorithms.For routers to cooperate they need to run the same routing algorithm.For this purpose topological areas have been defined: the same protocol is used within an area.10Overcoming the Problem of the Internet GrowthDefault routerTo prevent routing table size explosion only partial information is kept.Routers closer to backbones have more complete tables.The default entry specifies a route to be used for all IP packets whose destination is not included in the routing table.CIDRAllocates a batch of contiguous class C IP address to a subnet requiring more than 255 address;Allows to subdivide class B address space for allocation of multiple subnets;This is achieved by of a mask field by routing tables.A bit pattern that selects a portion of IP address to be compared with the routing table entry.11IP version 6A more permanent solution to the problem of the Internet growth.Address space: 2128Factor in inefficiencies of address allocation and still get about 1000 IP addresses per m2.Routing speed: the complexity of the header is reduced.Real-time and other special services: the header includes the priority and flow control fields.The use of these fields will depend on major improvements in the infrastructure (hardware) and suitable method of allocating and arbitrating resources.12IP version 6 (cont’d)Future evolution: next header field, which defines the type of an extension header that is included in the packet.Multicast and anycast: IPv6 supports anycast, or delivery to at least to one of the hosts among the relevant addresses.Security: IPv6 implements authentication and encrypted security payload extension header types.Equivalent to providing a secure channel;Means that the payload is encrypted and/or digitally signed.13Mobility and IPDynamic Host Configuration Protocol (DHCP)Designed to support the ability of a mobile device to maintain simple access to services;Assigns a temporary IP address to the device.To provide permanent access by clients to a mobile computer it must maintain a permanent IP address.Problem: IP routing is subnet-based.Subnets are at fixed locations.14MobileIPA transparent solution
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