Transcript Underlying Technologies

Underlying Technologies
CST 415
4/8/2016
CST 415 - Computer Networks
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Topics
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Definitions
Network Communications
Ethernet
FDDI
ATM
ARPANET
NSFNET
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Definitions
Connection Oriented Services
– Also called “circuit-switched” services.
– In this scheme, a dedicated circuit is created between
endpoints. An example of this is the current telephone
system.
– In this scheme, a physical communication circuit is
established between endpoints through intermediate
switching stations.
Advantage: Only the endpoint to endpoint traffic will traverse the
communication circuit. This guarantees a certain quality of service.
Disadvantage: Cost is fixed regardless of traffic. Also, any failure of
an intermediate connection will fail the entire connection.
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Definitions
Connectionless Services
– Also called “packet-switched” services.
– There is no dedicated circuit between endpoints.
– Communication is split up into small digitized chunks
(packets).
– End-to-end communication is potentially performed
through many different routes depending on network load.
Advantage: Communication redundancy provides a higher level of
throughput depending on system load.
Disadvantage: Reconstruction of packets is timely and data rate
cannot be guaranteed.
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Definitions
Full Duplex
– The communication media will allow concurrent
transfer of information in both directions.
– From the application point of view, it appears as
though there is a communication line for sending
and a line for receiving.
Half Duplex
– The communication media will only transfer in
one direction at a time such as a serial cable.
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Network Communications
LAN – Local Area Network
– Privately owned networks within a single
building or campus, typically spanning a few
kilometers as a maximum.
– Bandwidth can be high because of low distance
restrictions.
– Security internal to a LAN can be closely
monitored.
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Network Communications
LAN – Topologies
– Ring Topology (Token Ring)
– Bus Topology (Typically Ethernet)
A LAN can deploy any topology that the local system
administrator wishes.
Q: What will always be required if a LAN whishes to
interoperate with other LAN installations?
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Network Communications
from Computer Networks
by Andrew S. Tanenbaum
Two network topologies
(a) Bus
(b) Ring
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Network Communications
WAN – Wide Area Network
– Data networks that span large geographical
distances.
– Typical speeds are 1.5 Mbps to 155 Mbps.
– WAN data rates are usually slower that LAN
data rates.
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Network Communications
Subnet - a collection of
routers and communication
lines.
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from Computer Networks
by Andrew S. Tanenbaum
Wide Area Network
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Network Communications
from Computer Networks
by Andrew S. Tanenbaum
Relative network types and their
typical area coverage.
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Network Communications
• The Internet is not made up of homogeneous
networks.
• Ethernet is one type of physical transmission
standard/data link standard used for LAN
communications.
• Other packet switching technologies are
used for WAN and Internet.
– Frame Relay
– FDDI
– ATM
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Ethernet
The term Ethernet comes from the
luminiferous ether, the medium through
which electromagnetic radiation was thought
to propagate.
This was before it was discovered that
electromagnetic radiation could propagate in
a vacuum.
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Ethernet
• Developed at Xerox PARC in the early 70’s.
• IEEE Standard Number is 802.3
• Transceiver taps into the Ethernet cable
– Senses signals (CS)
– Sends signals
• NIC (Network Interface Card) adapts the
host computer to the transceiver.
• Multiple computers are connected to a single
cable to form a bus topology (MA).
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Ethernet (CSMA/CD)
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A computer decides to send a packet.
The carrier is active and there are no packets
currently being transmitted. (Carrier Sense – CS)
There are multiple computers on the network bus
(Multiple Access – MA)
It is possible and highly probable that more than
one machine will send at the same time.
The collision will be detected (Collision
Detection – CD)
The computers will back off for a random
amount of time and try again.
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Ethernet (CSMA/CD)
The amount of time the computer will “backoff” for is determined by a technique
known as “binary exponential backoff”.
1. For the first 10 attempts, the mean value of the
random delay is doubled.
2. For the next 6 attempts, the mean value is
maintained.
3. After 16 unsuccessful attempts, the computer
will give up and report a link error.
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Ethernet (CSMA/CD)
See 802.3
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Figure 4–3 Relationship among CSMA/CD
procedures
Figure 4–4a—Control flow summary send frame
Figure 4–4b—Control flow summary receive
frame
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Ethernet (CSMA/CD)
Thicknet
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10Base5 : The physical signal is carried over a coaxial
cable approximately ½ inch in diameter and up to 500
meters long. Theoretical transmission rate is 10 Mbps
Transceivers are directly connected to the coaxial
cable.
Drop cables connect the cable to the Ethernet
controller.
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Ethernet (CSMA/CD)
Thinnet
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10Base2 : The physical signal is carried over a coaxial
cable that is pliable and easy to run through ceilings,
floors and walls.
Span is up to 200 meters long.
Theoretical transmission rate is 10 Mbps
Transceivers are resident on controller cards resident
in host computers.
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Ethernet (CSMA/CD)
Twisted Pair Ethernet
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10BaseT : The physical signal is carried 4 unshielded
twisted pair wires that are resident in standard
telephone equipment (Category 5 or Cat5).
The cable is connected up to a hub that provides the
Bus topology.
Length of wire is limited to 100 meters.
Theoretical transmission rate is 10 Mbps
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Ethernet (CSMA/CD)
Fast Ethernet
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100BaseT : The physical signal is carried 4 unshielded
twisted pair wires that are resident in standard
telephone equipment (Category 5 or Cat5).
The cable is connected up to a hub that provides the
Bus topology.
Length of wire is limited to 100 meters.
Theoretical transmission rate is 100 Mbps.
The increase in rate is provided by clever use of the
provided 4 twisted pairs to increase data rate.
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Ethernet (CSMA/CD)
Gigabit Ethernet
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1000BaseT : The physical signal is carried 4
unshielded twisted pair wires that are resident in
standard telephone equipment (Category 5 or Cat5).
The cable is connected up to a hub that provides the
Bus topology.
Length of wire is limited to 100 meters.
Theoretical transmission rate is 1000 Mbps.
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Ethernet (CSMA/CD)
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Each of the Ethernet standards has a relatively short
physical limitation.
To extend the distance of a single network, an
administrator can employ:
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Repeater : simply amplify and propagate packet signal.
Bridges : repeat the packets with the intelligence of receiving a
good packet before passing it on.
Smart Bridges: only propagate those packets within a certain
address range.
Transport Bridge: perform a protocol conversion into a protocol
running over a “long-haul” network (e.g. ATM).
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Ethernet (CSMA/CD)
Standards –
10BASE2: IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD local area
network over RG 58 coaxial cable. (See IEEE 802.3 Clause 10)
10BASE5: IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD local area
network over coaxial cable (i.e., thicknet). (See IEEE 802.3 Clause 8.)
10BASE-F: IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD local
area network over fiber optic cable. (See IEEE 802.3 Clause 15.)
10BASE-FB port: A port on a repeater that contains an internal 10BASE-FB Medium
Attachment Unit (MAU) that can connect to a similar port on another repeater.
(See IEEE 802.3 Clause 9, Figure 15-1b and Figure 17.3.) 9ITU-T publications
are vailable from the International Telecommunications Union, Place des Nations,
CH-1211Geneva 20, Switzerland (www.itu.int/). 10For information on MatLab
contact: The MathWorks, 24 Park Way, Natick, MA, (www.mathworks.com).
IEEE Std 802.3-2002, Section One LOCAL AND METROPOLITAN AREA
NETWORKS: 12 Copyright © 2002 IEEE. All rights reserved.
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Ethernet (CSMA/CD)
Standards –
10BASE-FB segment: A fiber optic link segment providing a point-to-point connection
between two 10BASE-FB ports on repeaters. (See link segment IEEE 802.3
Figure 15-1b and Figure 15–2.)
10BASE-FL segment: A fiber optic link segment providing point-to-point connection
between two 10BASE-FL Medium Attachment Units (MAUs). (See link segment
IEEE 802.3 Figure 15-1c and Figure 15–2.)
10BASE-FP segment: A fiber optic mixing segment, including one 10BASE-FP Star
and all of the attached fiber pairs. (See IEEE 802.3 Figure 15–1a, Figure 1–3, and
mixing segment.)
1.4.8 10BASE-FP Star: A passive device that is used to couple fiber pairs together to
form a 10BASE-FP segment. Optical signals received at any input port of the
10BASE-FP Star are distributed to all of its output ports (including the output port
of the optical interface from which it was received). A 10BASE-FP Star is
typically comprised of a passive-star coupler, fiber optic connectors, and a suitable
mechanical housing. (See IEEE 802.3, 16.5.)
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Ethernet (CSMA/CD)
10BASE-T: IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD local
area network over two pairs of twisted-pair telephone wire. (See IEEE 802.3
Clause 14.)
100BASE-FX: IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD
local area network over two optical fibers. (See IEEE 802.3 Clauses 24 and 26.)
100BASE-T: IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD
local area network. (See IEEE 802.3 Clauses 22 and 28.)
100BASE-T2: IEEE 802.3 specification for a 100 Mb/s CSMA/CD local area
network over two pairs of Category 3 or better balanced cabling. (See IEEE
802.3 Clause 32.)
100BASE-T4: IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD
local area network over four pairs of Category 3, 4, and 5 unshielded twistedpair (UTP) wire. (See IEEE 802.3 Clause 23.)
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Ethernet (CSMA/CD)
100BASE-TX: IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD
local area network over two pairs of Category 5 unshielded twisted-pair (UTP)
or shielded twisted-pair (STP) wire. (SeeIEEE 802.3 Clauses 24 and 25.)
100BASE-X: IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD
local area network that uses the Physical Medium Dependent (PMD) sublayer
and Medium Dependent Interface (MDI) of the ISO/IEC 9314 group of
standards developed by ASC X3T12 (FDDI). (See IEEE 802.3 Clause 24.)
1000BASE-CX: 1000BASE-X over specialty shielded balanced copper jumper cable
assemblies. (See IEEE 802.3 Clause 39.)
1000BASE-LX: 1000BASE-X using long wavelength laser devices over multimode
and single-mode fiber. (See EEE 802.3 Clause 38.)
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Ethernet (CSMA/CD)
1000BASE-SX: 1000BASE-X using short wavelength laser devices over
multimode fiber. (See IEEE802.3 Clause 38.)
1000BASE-T: IEEE 802.3 Physical Layer specification for a 1000 Mb/s
CSMA/CD LAN using four pairs of Category 5 balanced copper cabling.
(See IEEE 802.3 Clause 40.)
1000BASE-X: IEEE 802.3 Physical Layer specification for a 1000 Mb/s
CSMA/CD LAN that uses a Physical Layer derived from ANSI X3.2301994 (FC-PH) [B20]11. (See IEEE 802.3 Clause 36.) CSMA/CD IEEE Std
802.3-2002, Section One
10BROAD36: IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD
local area network over single broadband cable. (See IEEE 802.3 Clause
11.)
1BASE5: IEEE 802.3 Physical Layer specification for a 1 Mb/s CSMA/CD local
area network over two pairs of twisted-pair telephone wire. (See IEEE 802.3
Clause 12.)
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Ethernet (CSMA/CD) – Frame
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Ethernet (CSMA/CD) – Frame
Preamble:
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56 bits of alternating 1’s and 0’s
Provided to help receiving interfaces
synchronize.
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Ethernet (CSMA/CD) – Frame
SFD (Start Frame Delimiter):
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The SFD field is the sequence 10101011.
It immediately follows the preamble
pattern and indicates the start of a frame.
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Ethernet (CSMA/CD) – Frame
Source and Destination Address:
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48 bits
I/G – Address belongs to an individual Enet controller or a group of
controllers (multicast). Set to 0 in the source address.
U/L – Universal is typical for all addresses encoded into the Ethernet
controller at time of manufacture. Local is typical for broadcast and
can potentially be used for multicast.
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Ethernet (CSMA/CD) – Frame
Source and Destination Address:
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A MAC sublayer address is one of two types:
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There are two kinds of multicast address:
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Individual Address. The address associated with a particular
station on the network.
Group Address. A multidestination address, associated with one
or more stations on a given network.
Multicast-Group Address. An address associated by higher-level
convention with a group of logically related stations.
Broadcast Address. A distinguished, predefined multicast
address that always denotes the set of all stations on a given
LAN.
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Ethernet (CSMA/CD) – Frame
Length/Type:
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Identifies the type of data being carried in
the frame (e.g. ARP, IP, etc. ).
Allows for Ethernet frames to be self
identifying.
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Ethernet (CSMA/CD) – Frame
General Comments:
maxValidFrame = maxUntaggedFrameSize –
(2 x addressSize + lengthOrTypeSize +
crcSize) / 8;
addressSize = 48 bits (6 octets)
lengthOrTypeSize = 16 bits (2 octets)
crcSize = 32 bits (4 octets)
maxUntaggedFrameSize = 1518 octets for 10, and 100
Mbps.
maxValidFrame = 1506 octets for an IP payload
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Ethernet (CSMA/CD) – Frame
General Comments:
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Each octet of a MAC frame is transmitted least
significant bit first.
The FCS is transmitted lowest order bit first.
minFrameSize is dependent on underlying
transmission (e.g. 64 octets for 100 Mbps)
If the data being sent is not large enough for the
fill the minimum frame, the frame will be
padded.
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FDDI
Fiber Distributed Data Interconnect
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Provides a data rate of 100 Mbps
Designed to use Fiber optical cable where data
is encoded in a pulse of light.
Based on a ring topology
Uses token passing to control access to the
information transmission media.
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FDDI
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Initially, there will be two rings with
traffic rotating in opposite directions.
Each node in the ring has the ability to
perform a loop back. This allows a FDDI
network to be a “self-healing” network
transport media.
When a node failure occurs, the faulty
node will be removed from the network by
neighbor nodes looping away from the
faulty node.
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FDDI
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FDDI
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FDDI never caught on as a LAN
technology.
Station management was too complicated
Hardware prices were too high
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ATM (Asynchronous Transfer
Mode)
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A Fiber-Optic based technology.
Designed to operate in LAN and WAN
environments.
Permits extremely high level of bandwidth
(gigabit speeds).
Must use a high-speed ATM switch.
ATM is a connection oriented service
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This allows service providers to charge based
on connection time.
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ATM (Asynchronous Transfer
Mode)
An ATM virtual circuit.
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ATM (Asynchronous Transfer
Mode)
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To establish a connection in a ATM network,
connection initiation requires the sending of a
connection setup packet.
As the connection packet is routed through the
network, it establishes a “virtual circuit”.
To increase efficiency, the ATM network
transmits small, fixed sized packets.
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53 bytes
5 header octets
48 “payload” octets
The ATM packet is called a “cell”
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ATM (Asynchronous Transfer
Mode)
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Since the protocol defines a fixed sized
packet, fragmentation never needs to be
performed.
Initial route setup can be done in hardware
because no packet fragmentation and reassembly needs to be done.
Broadcast can also be done in hardware
because of fixed packet size.
Like Ethernet, ATM does not guarantee
cell delivery.
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ARPANET
Advanced Research Projects Agency
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Awarded a contract to develop network
based technologies (contract awarded to
BBN Technologies).
Served as a major test bed for the major
packet switched networking technologies.
Tied major universities, military bases, and
government laboratories together.
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from Computer Networks
by Andrew S. Tanenbaum
ARPANET
The original ARPANET design.
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from Computer Networks
by Andrew S. Tanenbaum
ARPANET
Growth of the ARPANET (a) December 1969. (b) July 1970.
(c) March 1971. (d) April 1972. (e) September 1972.
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NSFNET
National Science Foundation
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Established to ensure network communications
remain available to scientist and engineers.
Established a US backbone, regional (mid-level)
networks, and campus (access) networks.
Mid-level networks attached to the backbone
network.
Access networks attached to mid-level networks.
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NSFNET
The NSFNET backbone in 1988.
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NSFNET
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NSFNET tied together several scientific
supercomputer centers (housing the then
“ultimate” Cray supercomputers).
NSFNET gained increasing popularity as
ARPANET was ramping down.
As use went up, the government stepped
out of the network administration and gave
it up to commercial “telcos” (PacBell,
Sprint, etc.).
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