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

Goal of Internetworking - Uniform - Universal - Hides network details/differences from user

Payload SD AC FC DAdd SAdd CRC ED FS

Up to 4550 bytes

Ethernet

Token Ring

Lecture 8

Internet Architecture

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

network network network network

router router router

A host computer connects to a physical network

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

Lecture 8

Internet TCP/IP 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

Internet TCP/IP reference model ISO 7-layer reference model

TCI/IP Protocols Application

Presentation

Session

FTP TEL

NET DNS SNMP DHCP

Transport TCP UDP

RTP

Inter-

Network IPv4/IPv6

ICMP IGMP

ARP RARP

Data link

Physical

Protocols defined by

the underlying networks

H

H

H

Message

Segment

Datagram

Frame

Bits

Session

Address

Internet

Address

Physical

Address

Application

SMTP

Message

Address H

MAC

Address

Port

Number

IP

Address

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

Lecture 8

Classful IP Addresses

- 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

class Prefix/Netid Suffix/Hostid

IPv4 Addresses: 32 bits

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

Lecture 8

A Classful Addressing Example

Class B Class B

Class A Class C

Lecture 8

Subnet and Classless Addresses - Many IP addresses are wasted in classful addressing !!! - 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: - Classless addressing: arbitrary boundary - Class Inter-Domain Routing (CIDR) notation: Examples: 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

200.31.7.64/26

200.31.7.0/26

200.31.7.192/26

200.31.7.128/26

200.31.7.1 200.31.7.60

200.31.7.66

200.31.7.125

200.31.7.130

200.31.7.189

200.31.7.194 200.31.7.253

Rest of the Internet

Site 200.31.7.0

…

… Subnet-1

Subnet-2

Subnet-3

Subnet-4

Netid Subnetid Hostid

Network IP address / Bit number of Netid

class Prefix/Netid Suffix/Hostid

More about subnet address in Wikipedia

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

Router

Lecture 8

Address Mask and CIDR Host Address

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

Lecture 8

Special IP Addresses

- 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., 127.1.2.3, 127.255.0.0

* 127.0.0.1 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.