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IP: The Internet Protocol

IP: The Internet Protocol. Kevin Bolding Electrical Engineering Seattle Pacific University. Internet Protocol. IP is by far the most common networking protocol Used to connect thousands of local internetworks together.

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IP: The Internet Protocol

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  1. IP:The Internet Protocol Kevin BoldingElectrical EngineeringSeattle Pacific University

  2. 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 TCP UDP IP ICMP Network ARP OSPF RIP ODI/NDIS Data Link NIC Driver Physical NIC/Media

  3. 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

  4. 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, eachtagged 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

  5. Total Length (bytes) Source Address IPv4 Header Identification Type of Service Destination Address 32 bits Fragment Offset Version HeaderLength Header Checksum Options + Padding Flags Time to Live Protocol 20 bytes minimum

  6. IPv4 Addressing 1-254 1-254 1-254 1-254 • Groups to the left specify the network, others the host • Network address is assigned by InterNIC • 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 • 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

  7. 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

  8. Flow Label Source Address 128-bit Payload Length IPv6 Header Note: Land area of earth = 247 m2 --> 281 = 1024 addresses/m2 Traffic Class 32 bits Version Destination Address 128-bit Next Header Hop Limit 40 bytes minimum

  9. 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

  10. 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

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