Transcript Enterprise Java Bean

Core Networking
2110472 Computer Networks
Natawut Nupairoj, Ph.D.
Department of Computer Engineering
Chulalongkorn University
Outline
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Overview
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Network infrastructure: from core to terminal.
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Telecommunication.
Broadband communication.
Basic terminologies.
Gigabit Network Cores
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Frame Relay.
ATM.
Overview
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Communication networks
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Voice network: telephone, RF, 1G mobile.
Data over voice: fax, modem, 2G mobile.
Data network: broadband (DSL), 3G mobile, VoIP.
The topology of the connection ?
1876 - Voice over Wire
Central Office (CO)
PSTN: Network of Local COs
Inter-Exchange Carrier (IEC)
• CO
• End Office
• Local Exchange Carrier
(LEC)
Local Loop
Internet: Global Data Network
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Founded by Department of Defense (DOD)
and National Science Foundation (NFS)
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ARPANET + MILNET.
Network of networks
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Build the whole network from several subnetworks.
High-performance core network switching
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Carry large traffic.
Similar to highway interconnecting Bangkok and
regional provinces.
ARPANET – Internet’s Daddy!
Core Network Switching
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Switching Technologies
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Packet Switching.
Circuit Switching.
Message Switching.
Cell Switching.
Core Networking (WAN) Technology
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Frame Relay.
ATM.
X.25
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Use to be a dominate core networking
delivery.
Designed to send Data over Voice
communication (in 1970)
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Error prone.
Link is not for data.
X.25 Philosophy
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Make sure that every transmission is correct.
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Tight error and flow control.
X.25 Exchange
Frame Relay
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Problem with X.25
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Very slow…..w.
Much better data link: Fiber optic
 Low error rate.
 Designed for data transmission.
How to improve speed ?
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Simplify the protocol
 Thinner protocol stack.
 Simple switching node = faster and better throughput.
No error or flow control
 Error and loss recovery is application responsibility.
Frame Relay Exchange
Frame Relay Characteristics
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PDU is called “Frame”
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Variable sizes … up to 1600 bytes.
Virtual Circuit and Connection Oriented.
Multiplex several VC in a link
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Using Datalink Control Identifier (DLCI)
DLCI is translated along the route (different for
each link).
DLCI
Frame Relay Characteristics
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If detect error, discard the frame.
Congestion control
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Congestion avoidance.
Prevent the congestion by controlling the
transmission rate at the source.
Committed Information Rate (CIR).
Congestion Control
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Too many packets … poor performance.
Why?
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Senders send very fast (increase the utilization).
Switches/Receivers are not fast enough.
Queue at the switches are getting longer.
More delay … poor performance.
Not enough queue, discard (or control).
Retransmission = more packets.
More delay … poor performance.
Congestion Control
Techniques
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There are several approaches to handle the
congestion
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Discard data.
Congestion recovery.
Congestion avoidance.
Congestion Recovery
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Start handling when congestion happens.
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Good utilization.
Bad when network is overloaded
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Bangkok traffics.
TCP/IP
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Mostly initiated by receiver.
Sending source-quench to the sender.
Reduce window-size.
Slow-start algorithm.
Frame Relay CIR
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Congestion avoidance
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Control how fast a source can send.
CIR = agreements between user and network.
If transmitting over CIR, the “over-CIR” frames are
marked
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Likely to be dropped during congestion occurs.
Leaky-Bucket algorithm
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Smooth the Bursty traffic.
A bucket of tokens and control the “dropping rate”.
Burst Transmission
Leaky Bucket Algorithm
ATM
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Problems
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Frame relay is still too slow.
Need to support multimedia traffic
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Data traffic is delay tolerance but not error tolerance.
Multimedia is the opposite.
Delayed too long = packet lost.
ATM = Asynchronous Transfer Mode.
ATM Characteristics
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Philosophy
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Simple data transmission: simple = fast.
 Fixed-length PDU = Cell.
 Low processing overhead.
 Minimal error and flow controls.
QOS – quality of service.
Connection oriented.
Congestion control
 Congestion avoidance: similar to Frame Relay.
 Traffic policing
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Not allow a new connection if the bandwidth is not enough.
ATM Characteristics
5 Bytes
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Fixed-size cell
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53 octets
 5 octets header
 48 octets data
low processing overhead
higher data rate
 155.52 and 622.08 Mbps
48 Bytes
ATM Protocol Layers
Voice
Cell
Data
Cell
Video
Cell
ATM Protocol Layers
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Physical Layer
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Optical fiber
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ATM Layer
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Cell-based
SDH/SONET-based
Service independent
Only define cell + logical connection
AAL Layer
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Service dependent
AAL Layer
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4 classes (5 types)
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class A: circuit emulation
class B: multimedia traffics
class C: data (connection oriented)
class D: data (connectionless)
What are the differences ?
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Cell loss ratio
Cell transfer delay
Cell delay variation
Summary
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Core Networking
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Frame Relay.
ATM.
References
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J. Kurose and K. Ross, Computer Networking: A Top-Down
Approach Featuring the Internet, Addison Wesley, 2001.
A. Tanenbaum, Computer Networks, 2nd edition, Prentice Hall
International, 1996.
And many more.