Unformatted text preview: 4.7 a. No. This would violate the principle of separation of layers. To layer (N – 1),
the N-level PDU is simply data. The (N – 1) entity does not know about the
internal format of the N-level PDU. It breaks that PDU into fragments and
reassembles them in the proper order.
b. Each N-level PDU must retain its own header, for the same reason given in (a). 4.8 Data plus transport header plus internet header equals 1820 bits. This data is
delivered in a sequence of packets, each of which contains 24 bits of network
header and up to 776 bits of higher-layer headers and/or data. Three network
packets are needed. Total bits delivered = 1820 + 3 × 24 = 1892 bits.
4.9 UDP provides the source and destination port addresses and a checksum that
covers the data field. These functions would not normally be performed by
protocols above the transport layer. Thus UDP provides a useful, though limited,
4.10 In the case of IP and UDP, these are unreliable protocols that do not guarantee
delivery, so they do not notify the source. TCP does guarantee delivery. However,
the technique that is used is a timeout. If the source does not receive an
acknowledgment to data within a given period of time, the source retransmits.
4.11 UDP has a fixed-sized header. The header in TCP is of variable length. -16- ...
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This note was uploaded on 02/20/2012 for the course ENC 3250 taught by Professor Dr.timothycerner during the Fall '11 term at UNF.
- Fall '11