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21. Spanning Tree Protocol (STP) IEEE Specification 802.1d is used to prevent routing loops. In Cisco Catalyst 5000 series switches, use BDPUs (Bridge Protocol Data Units) to determine the spanning tree topology. STP uses a Tree Algorithm (STA) to prevent loops, resulting in a stable network topology.
22. HTTP is the protocol used for accessing the World Wide Web services. HTTP operates over TCP/IP. TCP/IP is the protocol, which is used by all internet applications such as WWW, FTP, Telnet etc. IPX/SPX is proprietary protocol stack of Novell NetWare.
1.The term "Segments" is usually associated with Transport layer
2. The term "Packets" is usually associated with Network Layer and
3. The term "Frames" is usually associated with Data Link Layer
24. The port number used by TCP is 6 and that of UDP is 17.
TCP: TCP is a full-duplex, connection-oriented protocol. It incorporates error checking as well.
UDP (User Datagram Protocol): UDP is a thin protocol. UDP is a connectionless protocol. It doesn't contact the destination before sending the packet and doesn't care whether the packet is reached at the destination. UDP uses port number 6.
25. Switching methods:
26. WAN (Wide Area Network) devices extend the reach of LAN (Local Area Network) devices. WANs typically span over a wide area, such over multiple cities / countries. WANs are connected over serial lines that operate at lower speeds than LANs. Some of the WAN devices are:
27. Standard adopted for Ethernet CSMA/CD by IEEE Committee is 802.3. 100BaseT (Fast Ethernet) uses IEEE803.2u standard which incorporates CSMA/CD protocol.
28. DOD Model maps to OSI model as below:
|DoD Model||OSI Model|
|Process/ Application map||Application, Presentation, Session layers (layers 7,6,5).|
|Host-to-Host||ISO's Transport layer (layer 4).|
|Internet||Network layer (layer 3)|
|Network Access||Data Link and Physical Layers (layers 6,7)|
29. Routers can make alternate route decisions based on ICMP messages, if appropriate. Routers send an ICMP message if the destination is unreachable.
30. Port numbers are used by TCP/ UDP to set up sessions with other hosts. The following are the recommended port numbers:
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