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
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
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
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!
Internet
Connections
&
Packet Routing
Global
Internet
Connection
Visualization
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
TCI/IP Protocols
Application
Presentation
Session
FTP
TEL
NET
DHCPDNS
SNMPTransport
TCP
UDP
RTP
Inter-
Network
IPv4/IPv6
ICMP
IGMP
ARP
RARP
Data link
Physical
Protocols defined by
the underlying networks
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
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
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
Lecture 8
A Classful Addressing Example
Class B Class B
Class A
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
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
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
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
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.
