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Networks Overview ( Lei You ) Overview of Local Network Topology ( Ryan McKenzie ) Internetworking Protocol ( Benjamin A Pullen ) Mobile IP ( Hui Tan ) Overview What is a Network? Two or more computers are connected together by a medium and are sharing resources. These resources can be files, printers, hard-drives, or CPU number-crunching power. A network can consist of two computers connected together on a desk, or it can consist of many Local Area Networks (LANs) connected together to form a Wide Area Network (WAN) across a continent. The Big Picture Many individuals have asked to see the "Big Picture" of networking: How does everything . Where does Microsoft NT fit in with routers and the OSI layers? What about UNIX, Linux and Novell? The big picture in the following slide attempts to show all areas of networking and how they tie into each other. Graphical Symbols Used in the Big Picture Circles - Network Operating Systems Squares - Communication & cabling protocols (OSI Transport to Physical Layer) Storm Clouds - Telecommunications media or Information Providers that connect to the Internet Machine symbol - Network "linker" can be a bridge, router, brouter or gateway Jagged haphazard dotted line - the Internet Telecommunications Components of The Big Picture ISDN - Integrated Services Digital Network Private Branch Exchanges - PBXs, Key Systems Telcos - AT&T, Bell Telephone, Sprint, Telus DataPac & DataRoute - Packet switching and analog switching WAN protocols Cell Relay - Digital packet switching WAN protocol Frame Relay - Digital packet switching WAN protocol X.25 - Analog packet switching WAN protocol ATM - Asynchronous Transfer Mode WAN protocol World Wide Web - Hypertext-based multimedia system ADSL - Asymmetrical Digital Subscriber Line ISO/OSI Model The International Standards Organization (ISO) Open Systems Interconnect (OSI) is a standard set of rules describing the transfer of data between each layer in a network operating system. Each layer has a specific function. For example, the physical layer deals with the electrical and cable specifications. The OSI Model clearly defines the interfaces between each layer. This allows different network operating systems and protocols to work together by having each manufacturer adhere to the standard interfaces. The application of the ISO OSI model has allowed the modern multi-protocol networks that exist today. Seven Layers in the OSI Model 7. Application Layer (Top Layer) 6. Presentation Layer 5. Session Layer 4. Transport Layer 3. Network Layer 2. Data Link Layer 1. Physical Layer (Bottom Layer) ISO/OSI Model … The OSI model provides the basic rules that allow multi protocol networks to operate. Understanding the OSI model is instrumental in understanding how the many different protocols fit into the networking jigsaw puzzle. The Big Picture can be broken up according to its protocols into the following four areas: Local Loops LANs MANs WANs The Local Loop The Local Loop is often called "the last mile", and it refers to the last mile of analog phone line that goes from the telephone company's central office (CO) to your house. The Local Loop … Typical Local Loop Protocols Voice Lines Modem Connections – 56 kbps ISDN (Integrated Services Digital Network) - 2 x 64 kbps digital lines ADSL (Asymmetrical Digital Subscriber Line) - up to 8 Mbps * Cable Modems - up to 30 Mbps Cable modems are not part of the local loop but do fall into the category of the last mile, or how high speed digital communication gets to the premises (home). It would incredibly expensive to replace the existing cabling structure. And because this cabling was designed for voice communications rather than digital, all of these protocols are needed to overcome the existing cabling limitations in the local loop and provide high speed digital data transmission. Local Area Networks (LANS) A Local Area Network is a system of computers that share resources such as disk drives, printers, data, CPU power, fax/modem, applications, etc. They usually have distributed processing, which means that there are many desktop computers distributed around the network and that there is no central processor machine (mainframe). Local Area Networks (LANS) … Components Used by LANs Cabling standards Hardware Protocols LANS: Cabling Standards Cat 3, 4 and 5 cables IBM Type 1-9 cabling standards EIA568A and 568B Ethernet cabling standards: IEEE 802.3 (10Base5), IEEE 802.3a (10Base2), IEEE 802.3i (10BaseT) Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Connectors: RJ45, RJ11, Hermaphroditic connectors, RS-232, DB-25, BNC, TEE LANS: Hardware Devices Network Interface Cards (NICs) Repeaters Ethernet Hubs or multi port repeaters Token Ring Multi Station Access Units (MSAUs), Control Access Units (CAUs) and Lobe Access Modules (LAMs) Bridges LANS: Hardware Devices … Brouters Routers Gateways Print servers File servers Switches LANS: Examples of Protocols Ethernet frame types: Ethernet_II, Ethernet_SNAP, Ethernet_802.2, Ethernet_802.3 Media Access Control layer (MAC layer) Token Ring: IBM and IEEE 802.5 Logical Link Control Layer (LLC) IEEE 802.2 TCP/IP IPX/SPX Asynchronous Transfer Mode (ATM) Metropolitan Area Networks (MANs) A Metropolitan Area Network is a system of LANs connected throughout a city or metropolitan area. MANs have the requirement of using telecommunication media such as voice channels or data channels. Branch offices are connected to head offices through MANs. Examples of organizations that use MANs are universities and colleges, grocery chains, and banks. Metropolitan Area Networks (MANs)… Metropolitan Area Networks (MANs)… The main criterion for a MAN is that the connection between LANs is through a local exchange carrier (the local phone company). The protocols that are used for MANs are quite different from those used for LANs (except for ATM, which can be used for both under certain conditions). Examples of MAN Protocols RS-232, V-35 X.25 (56kbps), PADs Frame Relay (up to 45 Mbps), FRADs Asynchronous Transfer Mode (ATM) ISDN (Integrated Services Digital Network) PRI and BRI Dedicated T-1 lines (1.544 Mbps) and Fractional T-1 T-3 (45 Mbps) and OC-3 lines (155 Mbps) ADSL (Asymmetrical Digital Subscriber Line) - up to 8 Mbps XDSL (many different types of Digital Subscriber Lines) Wide Area Networks (WANS) WANs connect LANs together between cities Wide Area Networks (WANS) … The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers. Otherwise the same protocols and equipment are used as a MAN. References 1. Introduction to Networking and Data Communications Eugene Blanchard Edited by Joshua Drake, Bill Randolph and Phuong Ma 2. Computer Networking: A Top-Down Approach Featuring the Internet Jim Kurose & Keith Ross 3. Internetworking Technology Overview Cisco Systems 4. Internetworking Case Studies Cisco Systems Network Topology Overview of Network Topology and Case Study of Flat Neighborhoods Goals in Topology Design Reliable and Robust Fast and Efficient Simple and Scalable Examples of well known designs follow this slide, we shall assume all topologies are using 100 Mbit Ethernet as the medium and rate them on design categories. Bus Topology Robustness Efficiency Simplicity Scalability Bus Topology Robustness Good Efficiency Good Simplicity Excellent Scalability Fair Ring Topology Robustness Efficiency Simplicity Scalability Ring Topology Robustness Poor Efficiency Good Simplicity Very Good Scalability Poor Star Topology Robustness Efficiency Simplicity Scalability Star Topology Robustness Very Good Efficiency Very Good Simplicity Poor Scalability Excellent A New Topology is Born In the past, it has been standard to come up with a topology first, and then adapt it to certain tasks. Modern design philosophy has changed this practice. Now a subset of problems or needs gives rise to special task network designs. One such design has been conceived right here at UK. The Flat Neighborhood Network Brought about by the need to build a large cluster supercomputer from common networking components. Driven to evolve from the need for (more) efficient communication between cluster nodes. The Basics of FNN‟s This example shows how one could construct a FNN for 6 PCs using just two NICs/PC and three 4-port switches. Note that every PC has at least one single-switch latency path to every other PC; some PC pairs have more than one such path. Some NEW Design Problems Multiple small, interleaved subnets link each machine by a number of one-switch latency paths. Any machine can belong to as many subnets as it has network cards onboard. Sounds simple, but several problems arise from the design. Design of Subnets Wiring Scheme Routing and Efficient use of Addressing Bandwidth The Solutions: Subnets and Wiring The wiring scheme and subnets can now be designed by a piece of software developed in the KAOS lab. This problem appears to be NP Complete (Very Bad) and must be solved using a genetic search algorithm. A simplified version allows you to design your own FNN on the web. http://aggregate.org/FNN/ The Solutions: Genetic Search Algorithm Generate 256 random networks. Evaluate and rate each based on… Latency, Bandwidth Balance, Comm. Patterns Throw out bottom 2/3 results and replace with mutations thereof. Merge Subnets of pairs in top 1/3 results. Re-Evaluate and rate accordingly The Solutions: Basic Routing Each machine in the cluster swaps unique identifiers with all of its neighbors at boot up. Address resolution is done locally using the table that this swap generates. Non-Dynamic Solution The Implementation: KLAT2 Assembled on April 11, 2000 in the KAOS lab by Dr. Dietz and Mr. Mattox Fully Functional on April 16 The first working implementation of an FNN The Main Event: KLAT2 vs. Superdome KLAT2 vs. Superdome Round 1: Cost KLAT2 Total Value: $41,205 Peak Performance: 64 GFlops $643.83 / GF Superdome Total Value: $1.5M / yr Peak Performance: 672 GFlops $2,232.14 / GF / yr Advantage KLAT2 KLAT2 vs. Superdome Round 2: Upgrading KLAT2 Purchase new Nodes Upgrade the Old Nodes Recompute Scheme Rewire EVERYTHING Superdome Purchase a new Cabinet Plug and Play Advantage Superdome The Lowdown FNN‟s provide wonderful cost efficiency, but are plagued by limitations. Number if NIC‟s in each node PCI Bus Speed Increased Physical Distance Complexity of Design Use of KLAT2 KLAT2 is mainly a lab experiment, thus its practical uses are limited : Insufficient Non-Volatile Storage Weak Back-Up System Slow Internet Connection to the WAN Limited Application Compatability With further R+D, the FNN cluster may evetually bring about a “supercomputer in every home” movement. Summary Topology Development Philosophy has Evolved Special Purpose Topologies use Networks to Solve Specific Problems Network Topologies are Always Expanding More Topologies Being Concieved Faster, More Advanced Media The Credits Dr. Hank Dietz, (859) 257-4701 http://www.engr.uky.edu/ece/faculty/dietz/index.html Mr. Tim Mattox at the KAOS Lab, (859) 257-9695 http://aggregate.org/KAOS/ KAOS Lab Documentation and Publications on FNN‟s http://aggregate.org/FNN/ Dr. Craig Douglas, (859) 257-2326 http://www.ccs.uky.edu/~douglas/ Mr. John Connolly at the UK Center for Computational Sciences http://www.ccs.uky.edu/~connolly/ UK SDX Home Page http://sdx.uky.edu/ Internetworking Protocol Version 4 (IPv4) Topics: Why? What? How? Why IP? Why do we build networks? Why do we need inter-networks? What is IP? Protocol suit defining an interface between lower level hardware functionality and higher level application oriented protocols. Provides a “least common denominator” for all network hardware. Provides best effort service for datagram delivery from host to host. How? How? Fields Version(4 bits) – 4 Header Length(4 bits) – Size of the header in 4 byte words. Type of Service(8 bits) – Mostly unused. Length(16 bits) – Total length of IP datagram in bytes. Fields continued Identification(16 bits) – „unique‟ identifier Flags(3 bits) – 0, Don‟t fragment, More fragments. Fragment Offset(13 bits) – Offset of fragment in 8 byte words. Fields continued, again Time To Live (8 bits) – Hop count. Protocol(8 bits) – Higher level protocol address. Header Checksum – One‟s compliment sum of all 16 bit words in IP header. Fields, more? Source Address(32 bits) – Where it came from. Destination Address(32 bits) – Ummm, you know. Fields, will it ever end!? Options – options. Padding – even out to 32 bit words. Fragmentation IP only requires ~500 byte MTU from hardware layer but allows for packet sizes up to 65535 bytes. IP datagrams can be fragmented into smaller packets to travel over various networks then reassembled at the destination. Fragmentation Fragments from the same datagram carry the same identifier field. All fragments except the last have the More Fragments bit set. The Offset Field is an index into the original datagram payload. IP Addressing Hierarchical (cuz that‟s what CS people do) 32 Bits long. Globally unique (most of the time.) Assigned to network adapter, not host. Composed of network part and host part. Hosts on the same physical network have the same network address. IP Addressing Class A - [7 Bit Network][24 Bit Host] Class B - [14 Bit Network][16 Bit Host] Class C - [21 Bit Network][8 Bit Host] IP Addressing Classless IP addressing (the way it really is.) Arbitrarily long network portion followed by host portion. Can not tell dividing line from IP address. A netmask is used to divide the address. IP Forwarding Each host has a table with tuples of network addresses, address length, next hop information, and interface information. To forward an IP packet, find the longest network address that matches destination address. Send the packet out the corresponding interface to the next hop (may be local.) IP Forwarding Example: Interface0 = 184.108.40.206/24 Interface1 = 220.127.116.11/24 Address/Length Next Hop Interface 18.104.22.168/24 Local Interface0 22.214.171.124/16 126.96.36.199 Interface0 188.8.131.52/24 Local Interface1 0.0.0.0/0 184.108.40.206 Interface1 What‟s Next? IPv6 128 bit addressing (more people can play quake.) Fewer fields for simplicity Overview Mobility in the Internet Basic Mobile IP Protocol IMHP : Route Optimization in Mobile IP Other Issues Mobile Computers’ Characteristics May change point of network connection frequently May be in use as point of network connection changes Usually have less powerful CPU, less memory and disk space Less secure physically Limited battery power Current State of Mobile Computing Mobile computers are one of the fastest growing segments of the PC market Short-range wireless networks (Bluetooth) available from IBM, Toshiba, Dell, HP… High-speed (11 Mbps) wireless LAN products are now easily and cheaply available (IEEE 802.11a, IEEE 802.11b) Low speed (currently 128 Kbps) Metropolitan Area Wireless Network services are available in some cities and spreading (Metricom’s Ricochet) Mobility in the Internet Problem with current IP .It assumes that a node‟s IP address uniquely identifies its point of attachment to the Internet Mobility alternatives without Mobile IP .On moving, change IP address Use host-specific routes(using LSR) to reach mobile hosts .Mobility vs. Portability Functional Entities in Mobile IP Functional Entities in Mobile IP : -Mobile Node -Home Agent -Foreign Agent Each mobile node is assigned a unique home address within its home network When away from home network, it is assigned a care-of address either by : -Registering with a Foreign Agent -Obtaining a temporary IP address Basic Mobile IP H.A. Correspondent node F.A. M.H. Protocol Overview Agent Discovery Registration Tunneling Agent Discovery Extension of ICMP Router Discovery protocol Used by mobile nodes to discover Foreign Agents and to detect movement from one subnet to another Mobility Agents (H.A.s and F.A.s) periodically broadcast agent advertisements Agent Discovery (...contd.) Mobile node expects to receive periodic advertisements If it doesn‟t receive them, it deduces that either -it has moved OR -its agent has failed Mobile node can also broadcast Agent Solicitation messages Registration Mechanism by which M.H. communicates reachability info to its H.A. Registration messages create or modify a mobility binding at a H.A., which is then valid for a certain lifetime period Uses 2 control messages sent over UDP -Registration Request -Registration Reply Registration Authentication (..contd.) Replay Protection : Needed to ensure that registration messages are not replayed by a malicious host. Done using : -Nonces OR -Timestamps Registration Authentication Concern : Forged registrations permit malicious hosts to remotely redirect packets destined for the mobile host Default authentication between M.H. and H.A. uses MD-5 with a shared secret key No authentication between M.H. and F.A. Delivering Datagrams : When the mobile host is away, H.A. intercepts packets addressed to the M.H. and tunnels them to the M.H.s care-of address The tunneling scheme could use either of : - IP-in-IP Encapsulation -„Minimal‟ Encapsulation Delivering Datagrams (..contd.) Broadcast Datagrams -A H.A. forwards a broadcast datagram only if the M.H. requested forwarding of broadcast datagrams (in the registration request) Multicast Datagrams -M.H. can use a local multicast router -M.H. can use a bidirectional tunnel to its H.A. IMHP Extension to the basic Mobile IP protocol that features : -Route Optimization -Authentication of Management packets Defines four entities : -Mobile Hosts -Local Agents -Cache Agents -Home Agents Route Optimization (IMHP) Triangle Routing in basic Mobile IP -Limits performance transparency -Creates bottleneck at Home Agent H.A. Correspondent Node F.A. M.H. Route Optimization Eliminates triangle routing M.H. Any correspondent node can maintain a binding cache Correspondent node tunnels datagrams directly to the care-off address of the F.A. mobile host Correspondent Node H.A. Binding Management Four message types : -Binding Warning -Binding Request -Binding Update -Binding Acknowledge Lazy notifications are used (except MH to HA and previous FA) Foreign Agent Smooth Handoff As part of registration, M.H. requests its new F.A. to notify its previous F.A. New F.A. sends binding update to prev F.A. Previous F.A. updates its binding cache entry for the M.H. and sends a binding ack. Authentication of binding update is based on a shared registration key Special Tunnels When a F.A. receives a tunneled datagram for a M.H. for which it has no entry, it is tunneled back to the H.A. in a special tunnel Gives the datagram one more chance of successful delivery Avoids possible routing loops Authentication in IMHP IMHP has simple authentication procedures which preserve the level of security in today‟s Internet is defined to make use of strong authentication Authentication in IMHP (..contd.) M.H. to H.A. authentication -strong authentication based on a shared secret General Authentication -a random number specified in binding request is echoed in the reply by the H.A.
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