Know the OSI model layers AND the protocols under each.
Application: http, ftp, lpd, smtp, telnet, tftp, edi, pop3, imap, snmp, nntp, s-rpc, set
Presentation: ascii, ebcdicm, tiff, jpeg, mpeg, midi
Session: nfs, sql, rpc
Transport: spx, ssl, tls, tcp, udp
Network: icmp, rip, ospf, bgp, igmp, ip, ipsec, ipx, nat, skip
Data Link: slip, ppp, arp, rarp, l2f, l2tp, pptp, fddi, isdn
Physical: eia/tia-232, eia/tia-449, x.21, hssi, sonet, v.24, v.35
Know TCP/IP completely
What is the difference between tcp and udp? tcp is connection oriented and udp is connectionless
Know that the OSI model and the TCP/IP model.
Know well known ports
ports under 1023.
Know different cabling types and their lengths and max throughput rates.
stp: shielded twisted pair
10base-t utp
10base2 thinnet
10base5 thicknet
100base-t
1000base-t
fiber-optic
utp categories 1-7
Everything for this question can be answered by going here.
Be familiar with common LAN technologies
Ethernet: A system for connecting a number of computer systems to form a local area network, with protocols to control the passing of information and to avoid simultaneous transmission by two or more systems
Token Ring: A local area network in which a node can transmit only when in possession of a sequence of bits (called the token) that is passed to each node in turn
FDDI: Fiber-distributed data interface, a communications, cabling, and hardware standard for high-speed optical-fiber networks
Analog vs digital
Analog Versus Digital Transmission
| Feature | Analog Characteristics | Digital Characteristics |
| Signal | Continuously variable, in both amplitude and frequency | Discrete signal, represented as either changes in voltage or changes in light levels |
| Traffic measurement | Hz (for example, a telephone channel is 4KHz) | Bits per second (for example, a T-1 line carries 1.544Mbps, and an E-1 line transports 2.048Mbps) |
| Bandwidth | Low bandwidth (4KHz), which means low data transmission rates (up to 33.6Kbps) because of limited channel bandwidth | High bandwidth that can support high-speed data and emerging applications that involve video and multimedia |
| Network capacity | Low; one conversation per telephone channel | High; multiplexers enable multiple conversations to share a communications channel and hence to achieve greater transmission efficiencies |
| Network manageability | Poor; a lot of labor is needed for network maintenance and control because dumb analog devices do not provide management information streams that allow the device to be remotely managed | Good; smart devices produce alerts, alarms, traffic statistics, and performance measurements, and technicians at a network control center (NCC) or network operations center (NOC) can remotely monitor and manage the various network elements |
| Power requirement | High because the signal contains a wide range of frequencies and amplitudes | Low because only two discrete signals—the one and the zero—need to be transmitted |
| Security | Poor; when you tap into an analog circuit, you hear the voice stream in its native form, and it is difficult to detect an intrusion | Good; encryption can be used |
| Error rates | High; 10–5 bits (that is, 1 in 100,000 bits) is guaranteed to have an error | Low; with twisted-pair, 10–7 (that, is 1 in 10 million bits per second) will have an error, with satellite, 10–9 (that is, 1 in 1 billion per second) will have an error, and with fiber, 10–11 (that is only 1 in 10 trillion bits per second) will have an error |
synchronous vs asynchronous
Asynchronous means “not synchronous”.Synchronous means “agreed timing for the sending of ones and zeroes (bits)”–that is, the transmit and receive sides of the communications circuit have bothered to coordinate (synchronize) their signal and have agreed just what a digital bit encoded into the signal looks like. All communications paths have carrier signals, the signals have a frequency, and encoding bits into the signal involves spacing them out at regular intervals, and carving out just how long it takes to transmit a bit
baseband vs broadband
broadcast
multicast
unicast
csma
csma/ca
csma/cd
token passing
polling
