•Protocol: Identifies the protocol carried inside the next headerafter this IPv4 header – typically TCP or UDP.9IP Header Fields •Header Checksum: Allows error checking of IP packets•Source Address: 4-byte IPv4 source address for this packet•Destination Address: 4-byte IPv4 destination address for this packet 10
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 20186Ask Google for one?How do you get an IP address11Do you want astaticordynamicIP addressIt depends!
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 20187DHCP •Network admin can set static or dynamic address.•For dynamic, device will broadcast to Dynamic Host Configuration Protocol server •DHCP server will return the following valuesrequired to send IPv4 data:oIP AddressoSubnet MaskoDefault gateway addressoDNS server address13DHCP Server•DHCP server maintains pool of free IP addresses for each subnet and allocates with a lease time.•Device must renew IP address before lease time is up or the DHCP server will re-claim it.14
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 20188Example15What is a router!Network traffic goes throughrouters…16
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 20189What’s a Router?•A router is a device with multiple network interfaces.oEthernet interfacesconnect the router to Ethernet switchesoSerial interfacesconnect routers to other routers over point‐to‐point links•Each interface has its own IP address and subnet mask•Each interface connects to anIP subnetof devicesoFor us: subnet = Ethernet LAN or a point‐to‐point link17A Router’s jobSimply, forward packets from one IP subnet toanother IP subnet:•It receives packets on one interface•It looks up packet’s IP destination address in routing table•Itretransmitsthe packet out another interface to get it closer to itsdestination.18
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 201810With different tasksDifferent types of routers!Types of Routers•Wireless Home Routers combine a Wi-Fi access point, an Ethernet switch and a simple access router into a single box for home networking and Internet access across a DSL or Cable Modem connection.•Enterprise routers interconnect Ethernets within an business organization.20
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 201811Types of Routers•Access routers are used to connect home or business LANs to an Internet access link to an Internet Service Provider (ISP) router.•Backbone routers transport packets across the Internet backbone.21Now that we defined a routerUnderstanding aSubnet22
IT 263 & TDC 405 ‐ Autumn 201810 Oct 2018Dr. Oteafy © 201812What’s a subnet?•A subnet is a group of devices that can all send packets to each other withoutgoing through a router.
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