Internetworking and IP Address

Transcription

1 Lecture 8 Internetworking and IP Address Motivation of Internetworking Internet Architecture and Router Internet TCP/IP Reference Model and Protocols IP Addresses - Binary and Dotted Decimal IP Address - Classful IP Addressing - Subnet and Classless IP Addressing - Address/Subnet Mask - Special Addresses Assigning IP Address to Host Computer Assigning IP Addresses to Router

2 Motivation of Internetworking Lecture 8 Internetworking: networking technologies to connect multiple networks Many networks exist: LANs and WANs (Ethernet, Token Ring, FDDI, WiFi, BT, ) - No single networking technology suited for all needs - Computers in one type of network can t communicate with computer in another type - Repeater, bridge and hub connect only the same type of networks Universal service: Any pair of computers can communicate Heterogeneity and incompatibility among different networks - Media and electronic properties - Signaling and data encoding - Packet formats - Addresses - Protocols Ethernet Token Ring Goal of Internetworking - Uniform - Universal - Hides network details/differences from user SD AC FC DAdd SAdd Payload Up to 4550 bytes CRC ED FS

3 Lecture 8 Internet Architecture router router router network network network network A host computer connects to a physical network Internet building blocks: - Router * A hardware device with two or more interfaces to connect networks * A dedicated device/computer with CPU, memory, I/O, OS, etc. * Installed multiple NICs and network protocol suits when connecting different networks * Forwards packets from one network to another * Transforms packets as necessary to meet standards for each network * Sometimes called gateway if it can translate among different application protocols - Internet protocol suit * A software operated on different network protocols * A set of protocols, known as TCP/IP suite * Needed for both host computers and routers

4 Internet Concept - Create virtual network - Universal addressing scheme - Naming scheme - Implement with protocol software - All details of physical networks hidden from users Internet is a network of networks that interconnects millions of networks using routers and the Internet protocol suite (TCP/IP). No centralized governance! Each network sets its own policies. But must follow the name spaces, - Internet Protocol address space - Domain Name System (DNS)

5 Internet Connections

6 Internet Connections & Packet Routing Routers

7 Global Internet Connection Visualization

8 Lecture 8 Internet TCP/IP Reference Model Internet TCP/IP reference model ISO 7-layer reference model Layer 5: Application Layer Corresponds to ISO model layers 5, 6 and 7; used for communication among applications Layer 4: Transport Layer Corresponds to layer 4/5 in ISO model; provides reliable delivery of data Layer 3: Internet Layer (no such layer in ISO mode, extending network layer of ISO) Defines uniform format of packets forwarded across networks of different technologies and rules for forwarding packets in routers Layer 2: Network Interface Layer Corresponds to layer 2/3 in ISO model; defines formats for packets in hardware frame Layer 1: Hardware Layer Corresponds to layer 1 in ISO model; defines basic networking hardware

9 Application Presentation Session Transport FTP TEL NET TCP Application SMTP DHCP DNS SNMP RTP UDP TCI/IP Protocols H Message H Segment Message Address Session Address Port Number Inter- Network Data link Physical ICMP IGMP IPv4/IPv6 ARP Protocols defined by the underlying networks RARP H Datagram Frame Bits Internet Address Physical Address H IP Address MAC Address

10 Lecture 8 IP Address IP Address (Internet Protocol Address or Internet Address) - Abstraction only understood by software - Independent of hardware addressing - Used by TCP/IP protocols and other application programs - 32-bit integer, or 4 bytes - Does not identify a specific computer - Identifies a connection between a computer and a network - Unique value for a host (global/local address) - May have more than one IP addresses for a device/computer, e.g., a router - Classful IP addressing - Classless IP addressing - Assigned by global authority (IANA/ISP) and local administrator * IANA: Internet Assigned Number Authority * ISP: Internet Service Providers

11 Classful IP Addresses Lecture 8 IPv4 Addresses: 32 bits class Prefix/Netid Suffix/Hostid - Initial bits determine class: A, B, C, D, E - Prefix identifies a network: Network ID number - Suffix identifies a host/router: Host ID number - Class determines boundary between prefix & suffix - Global authority assigns unique prefix to network - Local administrator assigns prefix &/ unique suffix

12 Lecture 8 Dotted Decimal Notation of IP Addresses - 32 bit binary number is hard to remember - Divide 32 bits into four 8-bit sections called octet - Express each octet as a decimal number between 0 to Separate 4 decimal number by dot. - Easy for human and used by application programs More about IP address in Wikipedia

13 A Classful Addressing Example Lecture 8 Class B Class B Class A Class C

14 Subnet and Classless Addresses Lecture 8 - Many IP addresses are wasted in classful addressing!!! class Prefix/Netid Suffix/Hostid - Example: 4 Labs each having 60 computers, 4 class C network ID needed, ¾ addresses wasted - Three fixed division boundaries between prefix (Netid) and suffix (Hostid) in classful addressing - Subnet addressing: Netid Subnetid - Classless addressing: arbitrary boundary - Class Inter-Domain Routing (CIDR) notation: Examples: Hostid Network IP address / Bit number of Netid /16 first 16 bits is network ID, corresponding class B /26 first 26 bits is network ID Site Subnet / /26 Subnet-2 Subnet /26 Router Rest of the Internet /26 Subnet More about subnet address in Wikipedia

15 Address Mask and CIDR Host Address Lecture 8 Address mask or subnet mask: - defines the boundary between network/subnet ID and host ID - 32-bit binary number, e.g., (NetID in first 16 bits) - Bit mask makes computation efficient with logic and : A==D & M Example: Host IP bit subnet mask & Subnet ID CIDR host addresses 1 - ISP assigns CIDR prefix /28-4 bits (16 addresses) for subnet - Local administrator can assign a 4-bit value to a host - But leave two special addresses: all 0s/0000 and all 1s/1111

16 Special IP Addresses Lecture 8 - Some addresses have special meanings - This computer address means the computer sends the packet with all-0s - Network address refers to the network and not to the host - Directed broadcast address for broadcasting in a specified network - Limited broadcasting address for broadcasting in local network attached - Loopback address for sending a packet back to a computer itself. * The packet never leaves the computer * The packet goes from one application to another in the same computer * 127.x.y.z any address with head 127, e.g., , * is often used in test programming - All-1s and all-0s can not be assigned to any computer or router in a subnet!

17 IP Addressing Principle for Router Lecture 8 - Router connects to two or more physical networks - Each physical network has a unique prefix (Netid) - Router has multiple IP addresses, each for a connected network - Suffix in router IP address is assigned locally, like other host - Same suffix in routers IP addresses can help network administration Check your PC s - Physical/MAC address - IP addresses - Subnet Mask Using Command Prompt ipconfig ipconfig /all

18 Exercise 8 1. Describe similarities and differences between a network bridge and Internet router. 2. Describe similarities and differences between Internet reference model and ISO 7-layer model. 3. Identify the address class of the following IP addresses: a b c d e f g Point out which are special addresses. If an address is a host/router IP address in Class A, B or C, indicate its prefix (network ID) and suffix (host ID). 4. A small organization has a Class C address ( ) for seven networks each with 24 hosts. Design an appropriate subnet addressing scheme (subnet addresses, host addresses and mask) for the organization. 5. Draw a TCP/IP internet that consists of two networks connected by a router. Show two computers attached to each network. Assign the IP addresses to the four computers and one router with the assumption that network prefixes or IDs of the two networks are /18 and /29, respectively.