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CS 2200
Presentation 21
Networking
Questions?
Our Road Map
Processor
Networking
Parallel Systems
I/O Subsystem
Memory Hierarchy
Overview• Today
– A Brief History– Basic Concepts– Network Hardware– Ethernet
• Network Protocols
• Distributed Systems
• Remote Procedure Calls (RPC)
A Brief History• 1876 Telephone Invented
(Analog technology)
• 1942 Mainframes DevelopedUse continues today
Initially batch oriented environment
Evolution to Timesharing i.e. Data terminals connected to mainframes
• Early 60's Voice telephony switches to digital
A Brief History• 1960 AT&T Introduced Dataphone
– First commercial modem– Modem: Modulator/Demodulator– Convert between digital and analog signals– (Essentially same technology used today)
A Brief History• 1965 DoD Advanced Research Projects
Association begins work on ARPANET
• 1968/9 Carterphone decision allowed devices which were beneficial and not harmful to the network to be connected to the Public Switched Telephone Network (PSTN).Paved the way for computers to communicate using the telephone switching infrastructure.
A Brief History• 1969 ARPANET connects 4 computers
Stanford Research Institute, UCLA, UC Santa Barbara, and the University of Utah
• 1971 The ARPANET grows to 23 hosts connecting universities and government research centers around the country.
• 1971 Intel introduces the first microprocessor - the Intel 4004.
A Brief History• 1971 The Kenbak-1, the first
microcomputer, is introduced in Scientific American, selling a total of 40 units in 2 years.Used 130 IC's with a 256 byte memory and 8-bit words, processed 1000 instructions per second, and cost $750.
A Brief History• 1972 Intel launches the 8-bit 8008 - the
first microprocessor which could handle both upper and lowercase characters.
• 1972 Xerox develops the Xerox Alto - the first computer to use a Graphic User Interface.
The Alto consists of four major parts: the graphics display, the keyboard, the graphics mouse, and the disk storage/processor box. Each Alto is housed in a beautifully formed, textured beige metal cabinet that hints at its $32,000 price tag (1979US money). With the exception of the disk storage/processor box, everything is designed to sit on a desk or tabletop
A Brief History• 1973 Robert Metcalfe invents the Ethernet
networking system at the Xerox Palo Alto Research Center.
A Brief History• 1973 The ARPANET goes international
• 1974 Intel introduces the 8080 microprocessor– 5 times faster than the 8008. – And the heart of the future Altair 8800.
A Brief History• 1975 MITS markets the Altair 8800 - the
first mass-market microcomputer, launching the Personal Computer Revolution.
• 1975 Internet operations transferred to the Defense Communications Agency
• 1975 Bill Gates and Paul Allen form the Microsoft company to create software for the new Altair 8800.
A Brief History• 1976 Apple Computer is formed by Steve
Jobs, Steve Wozniak, and Ron Wayne, and launches the Apple Computer.
• 1977 Tandy Radio Shack ships its first personal computer - the TRS-80. It sells over 10,000 units, tripling expectations.
• 1977 Apple Computer launches the Apple II, which sets new standards for sophisticated personal computer systems.
A Brief History• 1978 The C programming language is
completed at AT&T Bell Laboratories, offering a new level of programming.
• 1978 Apple and Tandy ship PCs with 5.25" floppy disks, replacing cassette tape as the standard storage medium for PCs.
• 1978 Hayes Microcomputer Products releases the first mass-market modem, transmitting at 300 bps (0.3K).
A Brief History• 1978 Intel ships the Intel 8086
microprocessor, with 29,000 transistors, and running at 4.77 megahertz.
• 1979 Personal Software creates VisiCalc for the Apple II, the first electronic spreadsheet program, selling over 100,000 copies.
• 1979 Intel develops the 8088 microprocessor, which would later become the heart of the IBM PC.
A Brief History• 1979 Motorola develops the Motorola
68000 microprocessor, offering a new level of processing power.
• 1980 Seagate Technology introduces the first microcomputer hard disk, capable of holding 5 megabytes of data.
• 1980 Philips introduces the first optical laser disk, with many times the storage capacity of floppy or hard disks.
A Brief History• 1980 Xerox creates Smalltalk - the first
object-oriented programming language.
• 1980 John Shoch at Xerox creates the first “worm” program, with the capacity to travel through networks.
• 1981 Ungermann-Bass ships the first commercial Ethernet network interface card.
A Brief History• 1981 Xerox introduces the Xerox Star
8010, the first commercial Graphic User Interface computer, for $16,000-$17,000.
• 1981 Microsoft supplies IBM with PC-DOS (which it would also sell as MS-DOS), the OS that would power the IBM PC.
• 1981 IBM brings to market the IBM PC, immediately establishing a new standard for the world of personal computers.
A Brief History• 1981 ARPANET has 213 hosts. A new
host is added approximately once every 20 days.
• 1982 The term 'Internet' is used for the first time.
• 1983 TCP/IP becomes the universal language of the Internet
Question• That last group of slides was swell
1. Strongly agree
2. Agree
3. Neutral
4. Disagree
5. Strongly Disagree
Types of Interconnections• Massively Parallel Processors (MPP)
– Thousands of nodes– Short distances
• Local Area Networks (LAN)– Hundreds of computers– Several kilometers– Traffic many to one (clients to servers)
• Wide Area Network (WAN)– Thousands of computers– Thousands of kilometers– Scalable
Types of Interconnections• Massively Parallel Processors (MPP)
– Tightly coupled– Share memory and sometimes clock
• Local Area Networks (LAN)• Wide Area Network (WAN)
– Loosely coupled– Do not share memory and clock– Each processor has its own local memory– Communication via networks
Basic Concepts
Machine A Machine B
Each machine has the ability to send a message to the othera.) Please send me the contents of address xb.) Here is the contents of address x
Thus, messages must contain an extra bit.
Each machine has the ability to send a message to the othera.) Please send me the contents of address xb.) Here is the contents of address x
Thus, messages must contain an extra bit.
Basic Concepts
• Messages are divided into parts– Payload or actual data to be transferred– Header (or trailer) data used to control the message
passing scheme
• System must be designed to work well with operating system.– Multiple Processes– Error Handling
0
1
Address
Data
Payload (32 bits)Header (1 bit)
0-Request1-Reply
Software Steps to Send• Application copies data into O.S. buffer
• Operating System– Calculates checksum– Includes checksum in header and/or trailer– Starts timer– Sends data to network interface hardware and
tells it to send message
• Wait...
Reception• Copy data from network hardware into operating
system buffer• Calculate checksum from data• If calculated checksum matches included
checksum – Send acknowledgement – Copy data into application space
• Else – Discard message– Wait for resend
Sender...• If acknowledgement arrives
– Discard copy of message in buffer
• If timer times out first– Resend data – Restart timer
Header(2 bits)
00=Request01=Reply
10=Acknowledge Request11=Acknowledge Reply
PayloadData
(32 bits)
Checksum(4 bits)
Protocols• Sequence of steps performed by software
to send and receive messages.
• Issues– Endianess– Duplicate messages– Queue full– etc.
• More next time...
There is an old network saying: Bandwidth problems can be cured with money. Latency problems are harder because the speed of light is
fixed--you can’t bribe God.
David Clark, MIT
Vocabulary Fun• Bandwidth
• Time of Flight
• Transmission Time
• Transport Latency
• Sender Overhead
• Receiver Overhead
Diagramatically
TIME
Sender Overhead
TransmissionTime
Time ofFlight
TransmissionTime
Receiver Overhead
Sender
Receiver
Transport Latency
Total Latency
Questions?
Questions?• Where do you connect the network to the
computer?
• Which media are available to connect computers together?
• What issues arise when connecting more than two computers
• Additional practical issues?
Connecting the Computer• Connection Point
– Memory Bus– I/O Bus
• Control– Polling– Interrupts
• Operating System Involvement
Connecting the Computer• Connection Point
– Memory Bus MPP– I/O Bus LAN/WAN
• Control– Polling Hybrid– Interrupts Approaches
• Operating System Involvement– Avoid invoking O.S. in common case
Hierarchy of Media• Twisted Pair
• Coaxial Cable
• Fiber Optics
Question• Why is twisted pair twisted?
1. Keeps cable from kinking i.e. adds strength
2. Avoids electromagnetic interference
3. Keeps matching pairs grouped together in large bundle cables
4. Invented by Dee Snyder
Media• Twisted Pair
– 1 Mb/Sec 2 km $0.23/m + $15– 20 Mb/sec 0.1 km $0.23/m
• Coaxial Cable– 10 Mb/sec 1 km $1.64 + $460
• Multimode Fiber– 600 Mb/sec 2 km $1.03 + $2000
• Single-Mode Fiber– 2000 Mb/sec 100 km $1.64 + $2000
Questions?
So far how many computers have we connected?
Connecting > 2• Shared Media
– Bus– Ethernet (Vampire Taps)– Coordination Mechanism– Carrier Sensing and Collision Detection– Broadcast
• Switched Media– Better utilization of bandwidth– Point to point
Node NodeNodeNode
Node
NodeNode
Node
Switch
More About Rings
• Token Ring– Nodes pass token from one to another– When you have token you can send
Comparison• Ethernet
– CSMA/CD allows any node to talk at any time unless two talk at the same time
– Efficient at low loads
– As the number of hosts increases performance degrades
• Token Ring– Token being passed
around ring only allows node holding token to talk
– Less efficient than Ethernet at low loads
– As number of nodes increases performance slows but performance is predictable
Connection vs. Connectionless• Phone System
– To make call a connection or circuit was connected (might be multiplexed).
– Not a bad idea for voice– Connection exists whether or not anyone is talking.– Limit is number of conversations NOT amount of data
• Postal System– Each piece of information is routed according to its
address– Long messages can be broken up into pieces or
packets (or frames).
Routing• Shared Media
– Message goes to all nodes. Each looks at address to determine if they are recipient
• Switched Media– Source-based routing
• Message specifies path to destination
– Virtual circuits• Temporary or permanent
– Destination-based routing• Deterministic• Adaptive• Random
Routing Policies• Store and Forward
• Wormhole
• http://www.johnlockhart.com/research/janet/
Congestion Control• Circuit switched
– “All circuits are busy”
• Packet switched– Deadlock– Reducing Congestion
• Packet discarding!• Flow control (Window used by TCP)• Choke packets
Questions?
The Ethernet
A drawing of the first Ethernet system by Bob Metcalfe.
Ethernet Evolution• X_Base_Y
– X stands for the available media bandwidth– Base stands for base band signaling on the
medium– Y stands for the maximum distance a station
can be from the vampire tap (i.e. Length of Attach Unit Interface)
Ethernet Evolution• 10_base_5 (1979-1985)
– 10 Mbits/Sec with base band signaling with a maximum station distance of 500 meters
– Thick shielded copper conductor used as the medium
MAU-Medium Access Unit
• 10_base_2 (1985-1993)– “Thin net”, “cheaper net”– Distance to the “station” shrinks to 200 meters– No more vampire taps– BNC* connector to connect the stations to the Attach
Unit Interface (AUI) cables, the AUI cables to the medium
– The medium is daisy-chained via the stations using the BNC connectors
*Bayonet Neil-Concelman, or
sometimes British Naval Connector
*Bayonet Neil-Concelman, or
sometimes British Naval Connector
• 10_base_T (1993-1995)– Attach Unit Interface (AUI) is a twisted pair of copper
wires
– AUIs from the stations come to a “hub” which is a multiplexor/transceiver
– Did away with the BNC connectors which were a source of “connector” problems
– Use phone jack technology (RJ45 connectors) to connect AUI cables to the hub
– Hubs are connected to other hubs using the same connectors (RJ45)
• 10_base_T (1993-1995) continued– All the hubs together form the entire medium– All the stations in the “same” collision domain– Hub is also usually called a repeater
More Ethernet• 10BROAD36 - 10BROAD36 is a seldom used Ethernet
specification which uses a physical medium similar to cable television, with CATV-type cables, taps, connectors, and amplifiers.
• 1BASE5 - 1BASE5 is a specification of Ethernet that runs at 1 Mb/s over twisted pair wiring. This physical topology uses centralized hubs to connect the network devices.
• FOIRL - Fiber Optic Inter-Repeater Link - This specification of the 802.3 standard defines a standard means of connecting Ethernet repeaters via optical fiber.
More Ethernet• 10BASE-F - 10BASE-F is a set of optical fiber medium
specifications which define connectivity between devices.
• 100BASE-T - 100BASE-T is a series of specifications that provides 100 megabit speeds over copper or fiber. These topologies are often referred to as Fast Ethernet.
• Gigabit Ethernet - Gigabit Ethernet provides speeds of 1000 Mb/s over copper and fiber.
Where will it end???
Broadband vs. Baseband• A baseband network has a single channel that is
used for communication between stations. Ethernet specifications which use BASE in the name refer to baseband networks.
• A broadband network is much like cable television, where different services communicate across different frequencies on the same cable.
• Broadband communications would allow a Ethernet network to share the same physical cable as voice or video services. 10BROAD36 is an example of broadband networking.
Current Technology• Most modern Ethernet networks use
twisted pair copper cabling or fiber to attach devices to the network. The 10BASE-T, 100BASE-T, and Gigabit Ethernet topologies are well suited for the modern cabling and fiber infrastructures.
Still Hungry?
http://www.faqs.org/faqs/LANs/ethernet-faq/
Ethernet• The various Ethernet specifications
include a maximum distance
• What do we do if we want to go further?
• Repeater– Hardware device used to extend a LAN– Amplifies all signals on one segment of a LAN
and transmits them to another– Passes on whatever it receives (GIGO)
• Knows nothing of packets, addresses
– Any limit?
Repeaters
R1
R2
R3
Repeaters
R1
R2
R3
Bridges• We want to improve performance over that
provided by a simple repeater
• Add functionality (i.e. more hardware)– Bridge can detect if a frame is valid and then
(and only then) pass it to next segment– Bridge does not forward interference or other
problems
• Computers connected over a bridged LAN don't know that they are communicating over a bridge
Bridges• Typical bridge consists of conventional
CPU, memory and two NIC's.
• Does more than just pass information from one segment to another
• A bridge can be constructed to– Only pass valid frame if necessary– Learn what is connected to network "on the
fly"
Bridges
Event Segment 1 List Segment 2 List
Bridge boots - -
U send to V U -
V sends to U U, V -
Z broadcasts U, V Z
Y sends to V U, V Z, Y
Y sends to X U, V Z, Y
X sends to W U, V Z, Y, X
W sends to Z U, V, W Z, Y, X
BRIDGE X Y ZU V W
Bridges• A bridge will connect to distinct segments
(usually referring to a physical length of wire) and transmit traffic between them.
• This allows you to extend the maximum size of the network while still not breaking the maximum wire length, attached device count, or number of repeaters for a network segment.
Switch
A
B
C
D
Virtual LANs
• VLANs may span bridges– Nodes 1 and 5 same VLAN; 2, 6, 7 same VLAN– All nodes on the same VLAN hear broadcasts from
any node on that VLAN– VLAN limits the traffic flow among bridges– A hierarchical network with only bridges results in a
switched ethernet with no collisions!
Bridge
1
2
34
Bridge
5
6
78
http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113ed_cr/switch_c/xcvlan.htm
Network Interface Card• NIC
– Sits on the host station– Allows a host to connect to a hub or a bridge– If connected to a hub, then NIC has to use
half-duplex mode of communication (i.e. it can only send or receive at a time)
– If connected to a bridge, then NIC (if it is smart) can use either half/full duplex mode
– Bridges learn Media Access Control (MAC) address and the speed of the NIC it is talking to.
Routers• Work much like bridges
• Pay attention to the upper network layer protocols – (OSI layer 3) rather than physical layer (OSI layer 1)
protocols.
• Will decide whether to forward a packet by looking at the protocol level addresses (for instance, TCP/IP addresses) rather than the MAC address.
Routers• Because routers work at layer 3 of the OSI
stack, it is possible for them to transfer packets between different media types (i.e., leased lines, Ethernet, token ring, X.25, Frame Relay and FDDI). Many routers can also function as bridges.
Routers• Repeaters and Bridges understand only Media
Access Control (MAC) addresses– Traffic flow between nodes entirely based on MAC
addresses• Packet from a host station: <mac-addr, payload>
• Routers understand IP addresses– Special board that sits inside a bridge– IP layer on all nodes send packets destined outside
the LAN to the router– Router sees a packet as: <ip-hdr, payload>
• uses the ip-hdr to route the packet on to internet
Question• Learns the network topology and does
not forward messages that don't need to be forwarded
1. Repeater
2. Bridge
3. Switch
4. Router
Question• Amplifies and reconditions signals to
extend network segment
1. Repeater
2. Bridge
3. Switch
4. Router
Question• Allows multiple computers to
communicate with one another at the same time
1. Repeater
2. Bridge
3. Switch
4. RouterNode
NodeNode
Node
?
Question• Smartest of the bunch (i.e understands ip
addresses)
1. Repeater
2. Bridge
3. Switch
4. Router
Questions?
