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 Lecture 8

Lecture 8

Motivation of Internetworking

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

Lecture 8

Internet Architecture

router router router network network network A host computer connects to a physical network 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

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)

Internet Connections

Internet Connections & Packet Routing

Routers

Global Internet Connection Visualization

http://en.wikipedia.org/wiki/Internet

Internet TCP/IP Reference Model

Lecture 8 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

Application Application Presentation FTP TEL NET SMTP DHCP DNS SNMP Session Transport

TCP

UDP RTP Inter Network ICMP IGMP

IPv4/IPv6

ARP RARP Data link Physical Protocols defined by the underlying networks

TCI/IP Protocols

H Message Message Address Session Address Segment H

Port Number

Datagram H Internet Address

IP Address

H Physical Address

MAC Address

Frame Bits

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 Classless

IP addressing IP addressing - Assigned by global authority (IANA/ISP) and local administrator * IANA: Internet Assigned Number Authority * ISP: Internet Service Providers Lecture 8

Lecture 8

Classful IP Addresses

IPv4 Addresses: 32 bits class Prefix/Netid Suffix/Hostid -

Initial Prefix

bits determine class: A, B, C, D, E 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

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 255 - Separate 4 decimal number by dot “.” - Easy for human and used by application programs More about IP address in Wikipedia http://en.wikipedia.org/wiki/IP_address

A Classful Addressing Example

Class B Class B Lecture 8 Class A Class C

Lecture 8

Subnet and Classless Addresses

- Many IP addresses are wasted in classful addressing !!!

- Subnet addressing: Examples: Netid Subnetid - Classless addressing: arbitrary boundary - Class Inter-Domain Routing (CIDR) notation: Hostid class Prefix/Netid Network IP address / Bit number of Netid 128.211.0.0/16 first 16 bits is network ID, corresponding class B 200.31.7.0/26 first 26 bits is network ID 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 200.31.7.66

200.31.7.1

…

200.31.7.60

Subnet-1

200.31.7.0/26

Subnet-2

200.31.7.64/26 Rest of the Internet 200.31.7.125

200.31.7.130

200.31.7.128/26

Subnet-3

Router 200.31.7.189

Site 200.31.7.0

200.31.7.192/26 200.31.7.194

… Subnet-4

200.31.7.253

More about subnet address in Wikipedia http://en.wikipedia.org/wiki/Subnet_address

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., 11111111 11111111 00000000 00000000 (NetID in first 16 bits) - Bit mask makes computation efficient with “logic and”: A==D & M Example: Host IP 200.31.7.130 11001000 00011111 00000111 10000010 26-bit subnet mask 11111111 11111111 11111111 11000000 & Subnet ID 200.31.7.128 11001000 00011111 00000111 10000000 CIDR host addresses - ISP assigns CIDR prefix 128.211.0.16/28 - 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

1

Special IP Addresses

Lecture 8 - Some addresses have special meanings

This computer

address means the computer sends the packet with all-0s

Network address 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

* 127.0.0.1

 refers to the network and not to the host any address with head “127”, e.g., 127.1.2.3, 127.255.0.0

is often used in test programming - All-1s and all-0s can not be assigned to any computer or router in a subnet !

Lecture 8

IP Addressing Principle for Router

- 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

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. 200.58.20.165

b. 128.167.23.20

c. 127.54.118.21

d. 16.196.128.50

e. 193.34.121.255

f. 150.156.10.10

g. 230.10.24.96 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 (196.125.56.0) 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 170.61.192.0/18 and 210.37.136.32/29, respectively.