| A | B |
|---|
| Enterprises need: | 1) interconnected LANs that provide access to computers or file servers in other locations; 2) higher bandwidth onto the LANs to satisfy the needs of the end users 3) support technologies that can be relayed for WAN service |
| reasons for the division of network functions include | 1) to divide the interrelated aspects of network operations into less complex elements 2) to define standard interfaces for plug-and-play compatibility and multivendor integration 3) to enable engineers to focus their design and development efforts on a particular layer's functions 4) to promote symmetry of the different internetwork modular functions for the purpose of interoperability 5) to prevent changes in one area from significantly affecting other areas, so that each area can evolve more quickly 6) to divide the complex operations of internetworking into discrete, more easily learned operational subsets |
| 7 layers of OSI model | Application; Presentation; Session; Transport; Network; Data Link; Physical |
| PDUs | protocol data units |
| datagrams | The TCP segments become part of the network layer packets that are exchanged between IP peers |
| encapsulation | The wrapping of data in a particular protocol header. For example, Ethernet data is wrapped in a specific Ethernet header before network transit. Also, when bridging dissimilar networks, the entire frame from one network is simply placed in the header used by the data link layer protocol of the other network. |
| 5 steps of encapsulation | data to packets to segments to frames to bits |
| 3 basic LAN technologies | Ethernet, Token Ring and FDDI |
| 10BASE2 | (thin Ethernet) -- allows coaxial cable network segments up to 185 m. long |
| 10BASE5 | (thick Ethernet) -- allows coaxial cable network segments up to 500 m. long |
| 10BASE-T | carries Ethernet frames on inexpensive twisted-pair wiring |
| Carrier Sense Multiple Access with Collision Detection (CSMA/CD) | one node's transmission traverses the entire network and is received and examined by every node. When the signal reaches the end of a segment, terminators absorb it to prevent it from going back onto the segment |
| IP addresses | Network layer addresses exist at Layer 3 of the OSI reference model. Unlike data link layer addresses, which usually exist within a flat address space, network layer addresses are usually hierarchical. |
| MAC address | MAC sublayers define hardware or data link addresses called the MAC addresses |
| ARP | Address Resolution Protocol |
| TCP/IP environment | end stations communicate with servers or other end stations |
| Application Layer | supports the communicating component of an application. It does not provide services to any other OSI layer. However, it does provide services to application processes lying outside the scope of the OSI model (e.g. spreadsheet programs, Telnet, WWW, etc.) |
| Presentation Layer | formatting, compression and encoding |
| Session Layer | establishes, manages, and terminates sessions between applications |
| Transport | This layer segments and reassembles data into a data stream. TCP is one of the transport layer protocols used with IP. |
| Network | This layer determines the best way to move data from one place to another. |
| Data Link | This layer prepares a datagram (or packet) for physical transmission across the medium. It handles error notification, network topology, and flow control |
| Physical | This layer provides the electrical, mechanical, procedural, and functional means for activating and maintaining the physical link between systems. |
