Transcript EE 3760 chapter 7 - Seattle Pacific University

IP:
The Internet Protocol
Kevin Bolding
Electrical Engineering
Seattle Pacific University
Seattle Pacific University
IP - Internet Protocol
No. 1
Internet Protocol
• IP is by far the most common networking protocol
• Used to connect thousands of local internetworks
together
• IP is a network layer protocol, and is built on top of a
data-link and physical layer protocol
Transport
Network
TCP
ARP
IP
UDP
ICMP
OSPF RIP
Data Link
ODI/NDIS
NIC Driver
Physical
NIC/Media
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IP - Internet Protocol
No. 2
Datagrams
• Information to transmit may be anything from short messages
to continuous streaming contents
• IP is a packet-switching network
• Maximum size of message that may be sent in one datagram
• Each datagram must be 64KB or less
• Long (or continuous) messages must be broken into many
datagrams and sent separately
• Breaking messages into datagrams and reassembling them is
the job of a Transport Layer Protocol
• TCP (Transmission Control Protocol) makes long messages
appear continuous to the application
• UDP (User Datagram Protocol) provides less support, but is
more lightweight and faster in some situations
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IP - Internet Protocol
No. 3
The Multi-Layer Process
Reading a web page at facebook.com using a browser
1. Browser asks TCP to open a connection with www.facebook.com,
assigns a TCP session number (ex: 1432)
2. facebook.com asks TCP to send the web page data using session 1432
3. fackbook.com’s TCP sends components using datagrams in IP, each
tagged with session number 1432
Components < 64KB each take one datagram
Components > 64KB are split into multiple datagrams
4. IP passes the data through the network using routers
5. Your computer’s TCP client receives packets and reassembles them
6. Web page contents are delivered to your browser
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IP - Internet Protocol
No. 4
IPv4 Header
32 bits
20 bytes minimum
Version
Header
Length
Type of Service
Identification
Time to Live
Total Length (bytes)
Flags
Protocol
Fragment Offset
Header Checksum
Source Address
Destination Address
Options + Padding
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IP - Internet Protocol
No. 5
IPv4 Addressing
1-254
1-254
1-254
1-254
• Each IP address is 32 bits long
• 4 groups of 8 bits
• Each group can have numbers 1-254
• 0 and 255 are reserved for broadcast
• Groups to the left specify the network, others the host
• Network address is assigned by InterNIC
• Class A: Network.host.host.host
• Network is from 1-126, allows up to 16,000,000 hosts
• Class B: Network.network.host.host
• Network begins with 128 to 191, allows up to 64,000 hosts
• Class C: Network.network.network.host
• Network begins with 192-223, allows up to 254 hosts
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IP - Internet Protocol
No. 6
The IP problem
• We’re running out of IP addresses
• Solution A: Bigger IP - 128-bit address (IPv6)
• In the meantime
• 32 bits - 4 billion addresses ought to do…
• Squeezing the most out of the bits
• Private networks can have duplicate addresses
• 10.x.x.x, 172.16.x.x to 172.31.x.x, 192.168.0.x to 192.168.255.x
• Classless Inter-Domain Routing (CIDR)
• Forget classes, allow the number of network bits to be assigned
as desired (ex: 129.32.56.222/18 is between B and C size)
• Dynamic Host Configuration Protocol (DHCP)
• DHCP server maintains a list of available IP addresses
• Computers request IP address from DHCP server
• IP address is leased for a fixed amount of time; recycled
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IP - Internet Protocol
No. 7
IPv6 Header
40 bytes minimum
Version
Note: Land area of earth = 247 m2 --> 281 = 1024 addresses/m2
32 bits
Traffic Class
Payload Length
Flow Label
Next Header
Hop Limit
Source Address
128-bit
Destination Address
128-bit
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IP - Internet Protocol
No. 8
Interface to Lower Layers
• What does an Ethernet (or other Data-Link Layer
network) do with an IP message?
• Ethernet uses MAC addresses for routing
• IP address is nice, but useless
• ARP - Address Resolution Protocol
• Router/Host broadcasts an ARP Request
• Contains the IP address of desired destination
• Host with matching IP address responds
• ARP Reply broadcasts MAC address
• Caching
• Routers generally cache IP-to-MAC translations
• Need to refresh every now and then
Seattle Pacific University
IP - Internet Protocol
No. 9
IP Summary
• Network-layer protocol
• Used from LANs to The Internet
• Routers are the key
• Still going strong
• Basic form (IPv4) has been given new life
• CIDR, private networks
• DHCP allows it to work with rapidly changing
networks (I.e. laptops)
• The future
• IPv6 is coming…
• Bigger addresses, better addresses
Seattle Pacific University
IP - Internet Protocol
No. 10