18-03-2011, 06:36 PM
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| M.Arsalan Qureshi | | Join Date: Oct 2008 Location: Garden Town, Multan Cantt
Posts: 616
Program / Discipline: BSTS Class Roll Number: 09-31 | |
Network Layer: Internet Protocol Network Layer: Internet Protocol * The Address Resolution Protocol (ARP) is a dynamic mapping method that finds a physical address, given an IP address. * An ARP request is broadcast to all devices on the network. * An ARP reply is unicast to the host requesting the mapping. * IP is an unreliable connectionless protocol responsible for source-to-destination delivery. * Packets in the IP layer are called datagrams. * A datagram consists of a header (20 to 60 bytes) and data. * The MTU is the maximum number of bytes that a data link protocol can excapsulate. MTUs vary from protocol to protocol. * Fragmentation is the division of a datagram into smaller units to accommodate the MTU of a data link protocol. * The fields in the IP header that relate to fragmentation are the identification number, the fragmentation flags, and the fragmentation offset. * The Internet Control Message Protocol (ICMP) sends five types of error-reporting messages and four pairs of query messages to support the unreliable and connectionless Internet Protocol (IP). * ICMP messages are encapsulated in IP datagrams. * The destination-unreachable error message is sent to the source host when a datagram is undeliverable. * The source-quench error message is sent in an effort to alleviate congestion. * The time-exceeded message notifies a source host that (1) the time-to-live field has reached zero or (2) fragments of a message have not arrived in a set amount of time. * The parameter-problem message notifies a host that there is a problem in the header field of a datagram. * The redirection message is sent to make the routing table of a host more effective. * The echo-request and echo-reply messages test the connectivity between two systems. * The time-stamp-request and time-stamp-reply messages can determine the roundtrip time between two systems or the difference in time between two systems. * The address-mask request and address-mask reply messages are used to obtain the subnet mask. * The router-solicitation and router-advertisement messages allow hosts to update their routing tables. * IPv6, the latest verstion of the Internet Protocol, has a 128-bit address space, a resource allocation, and increased security measures. * IPv6 uses hexadecimal colon notation with abbreviation methods available. * Three strategies used to make the transition from version 4 to version 6 are dual stack, tunneling, and header translation.
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