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Static reservation of network resources
A guaranteed rate of throughput requires the commitment of resources that cannot be shared by other
network users. Unless full, uninterrupted throughput is required for the communication, bandwidth is
not used efficiently.
Connection-oriented services are useful for transmitting data from applications that are intolerant of
delays and packet re-sequencing. Voice and video applications are typically based on connection-
oriented services.
*Keypoints:Positive acknowledgement requires packets to be retransmitted if an acknowledgement is notreceived by the time a timer expires.Know that subnetting takes place in the Network layer of the OSI model.Know the 3 phases of connection oriented communication.Know that a disadvantage to using a connection oriented protocol is that packet acknowledge-ment may add to overhead.Connectionless-orientated
Connectionless communication is supported by UDP on port 17. It is not guaranteed and acknow-
ledgements are NOT sent or received. It is faster than connection orientated. It is up to the application
or higher layers to check that the data was received.
Connectionless network service does not predetermine the path from the source to the destination sys-
tem, nor are packet sequencing, data throughput, and other network resources guaranteed. Each packet
must be completely addressed because different paths through the network might be selected for differ-
ent packets, based on a variety of influences. Each packet is transmitted independently by the source
system and is handled independently by intermediate network devices. Connectionless service offers
two important advantages over connection-oriented service:
Dynamic path selection
Because paths are selected on a packet-by-packet basis, traffic can be routed around network failures.
Dynamic bandwidth allocation
Bandwidth is used more efficiently because network resources are not allocated bandwidth that they are
not going to use. Also, since packets are not acknowledged, overhead is reduced.
Connectionless services are useful for transmitting data from applications that can tolerate some delay
and re-sequencing. Data-based applications are typically based on connectionless service.
*Keypoints:Bandwidth requirement and overhead traffic are reduced because packets are not acknowl-edged in a connectionless environment.UDP is unreliable and unacknowledged.Data Link and Network AddressingMAC Addresses
Uniquely identifies devices on the same medium. Addresses are 48 bits in length and are expressed as
12 hexadecimal digits. The first 6 digits specify the manufacturer and the remaining 6 are unique to the
host. An example would be 00-00-13-35-FD-AB. No two MAC addresses are the same in the world.
Ultimately all communication is made to the MAC address of the card. Protocols such as ARP and
RARP are used to determine the IP to MAC address relationship. MAC addresses are copied to RAM
when a network card is initialized.