CSC469/CSC569
Homework #1
Szu-Ting Christina Po
1.PART 1
#R1
End systems are also referred to as hosts because they host(that is, run) application programs such as a
Web browser program, a Web server program, an e-mail reader program, or an e-mail server program.
The computers and other devices connected to the Internet are often referred to as end systems. They
are referred to as end systems because they sit at the edge of the Internet. The Internet’s end system
include desktop computers(e.g., desktop PCs, Macs, and Linux boxes), servers(e.g., Web and e-mail
servers), and mobile computers(e.g., portable computers, PDSs, and phones with wireless Internet
connections).
Yes, a Web server is an end system.
#R4
1. Residential access – dial-up modem over an ordinary analog telephone line into a residential ISP.
A pair of modems along with a point-to-point phone line.
2. Residential access – digital subscriber line(DSL) over an ordinary phone line. It is broadband.
3. Residential access – hybrid fiber-coaxial cable(HFC) over cable using cable modem. It is
broadband. It is extension of the current cable network used for broadcasting cable television.
4. Residentail access – satellite link.
5. Company access- Ethernet Local Area Network
6. Wireless Access – wireless LAN(wireless Ethernet and WiFi)
7. Wireless Access – wide area wireless access network(cellular telephone system)
#R5
The HFC transmission rate is shared among users. Collisions are not possible in a downstream HFC
channel, because all users have a single source of information.
#R8
Twisted-pair copper wire or coaxial cable.
#R9
Dial-up modems – dedicated, 56 kbps. Usually, 40 kbps.
DSL -dedicated, Verizon :768 kbps to 1.5 Mbps for downstream, 128 kbps to 768 for upstream.
HFC – shared. Provide higher bandwidth than DSL. But its bandwidth is shared by the entire
neighborhood. State of transmission can not quaranteed.
#R11
Circuit-switching is more suitable for real time services(for example, telephone calls and video
conferencing calls) than the packet-switching. It will not lose data. It is more reliable than the Packetswitching. Packet-switching can have variable and unpredictable end-to-end delay. With TDM, each
circuit gets all of the bandwidth periodically during brief interval of times. With FDM, each circuit
continuously gets a fraction of the bandwidth. For FDM, there may be interference between the
adjacent circuits. Error checking needs to be build into the FDM. Error checking will use bandwidth. So
TDM is more efficient than FDM.
#R12
Packet switching allocates link use on demand. Link transmission capacity will be shared on a packet-bypacket basis only among those users who have packets that need to be transmitted over the link. Such
on-demand (rather than pre-allocated) sharing of resources is sometimes referred to as the statistical
multiplexing of resources. For a TDM link, time is divided into frames of fixed duration, and each frame
is divided into fixed number of time slots. When the network establishes a connection across a link, the
network dedicates one time slot in every frame to this connection. These slots are dedicated for the
sole use of that computer, with one time slot available for use(in ever y frame) to transmit the
connection’s data. It is pre-allocated, not on demand.
2.PARTS 2
#1.
Picture frames, home electical and security system, environmental sensing devices.
#2.
For each transmitter-receiver pair, the bit is sent by propagating electromagnetic waves or optical pulses
across a physical medium. Physical medium fall into two categories: guided media and unguided media.
With unguided media, the waves propagate in the atmosphere and in outer space, such as in a wireless
LAN or digital satellite channel.
#3.
Twisted-pair copper wire, coaxial cable, multimode fiber-optic cable.
#4
Simplex – transmission can be done in only 1 direction
half-duplex – transmission can be done both directions. But at any one time, transmission can be done
in only 1 direction.
Full-duplex- transmission can be done in both directions simultaneously at any time.
#5.
1. The electrical current has to travel in circle.
2. The wires are twisted together to reduce the electrical magnetic interference from similiar pairs
close by.
3. for duplex transmission. Each pair is one direction.
4. For extra telephone line.
#6.
Different grade of twisted pairs.
RJ11 – 4 pairs of twisted pairs(8 wires) 10 MB per second. It is used for the DSL modem interface with
the phone line.
RJ45 – Ethernet LAN running at 100 Mbps. It is more twisted and more reliable. It is for data.
#7.
1.LAN- local area network, single building or single campus
2.WAN-wide area network, region, state,country,continent, planet
3.MAN-metropolitan area network, city
4.PAN-personal area network,bluetooth
#8.
Bluetooth is a wireless protocol for exchanging data over short distances from fixed and mobile devices,
creating personal area networks(PANs). It was originally conceived as a wireless alternatives to RS232
data cables.
#9.
Topology of a network is pattern of interconnection.
Bus topology, ring topology, star topology, mesh topology
#10.
Connect 2 devices
#11.
Intenentwork is networks of networks. Computer network is network of computers. It is part of the
intenetwork.
#12.
A machine is in more than one network. It is called a router.