Transcript Prof. Xi Zhang

ECEN 619-600 “Internet Protocols and
Modeling”
Course Materials: Papers, Reference Texts: Bertsekas/Gallager, Stuber, Stallings, etc
Grading (Tentative): HW: 20%, Projects: 40%, Exam-1:20%, Exam-II:20%
Lecture notes and Paper Reading Lists: available on-line: TBA
Class Website: http://ece.tamu.edu/~xizhang/ECEN619/start.php
Research Interests and Projects: URL:http://ece.tamu.edu/~xizhang
Instructor: Professor Xi Zhang
E-mail: [email protected]
Office: WERC 331
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP Closed-loop flow control and “Self-Clocking”
Principle-1
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP Closed-loop flow control and “Self-Clocking”
Principle-2
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Sender sends packets back-to-back to receiver
The vertical line is bandwidth
The horizontal line is time
Each of shaded box is a packet
Bandwidth * Time = Bits, and so the area of each box is
the packet size.
• The number of bits doesn‘t change as a packet goes
through the network so a packet squeezed into the smaller
long-haul bandwidth must spread out in time.
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP Closed-loop flow control and “Self-Clocking”
Principle-3
• The time Pb represents the minimum packet spacing on the
slowest link in the path (the bottleneck).
• As the packets leave the bottleneck for the destination net,
nothing changes the inter packet interval so on the
receiver’s net packet spacing Pr = Pb.
• If the receiver processing time is the same for all packets,
the spacing between ACKs on the receiver’s net Ar = Pr =
Pb.
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP Closed-loop flow control and “Self-Clocking”
Principle
• If the time slot Pb was big enough for a packet, it’s
big enough for an ACK so the ACK spacing is
preserved along the return path. Thus the ACK
spacing on the sender’s net As= Pb.
• So, if packets after the first burst are sent only in
response to an ACK, the sender’s packet spacing
will be exactly match the packet time on the
slowest link in the path –> “Self-Clocking” is
achieved.
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Two versions of TCP Protocols
• TCP-tahoe (Jacobson, 1988)
– Time-out based protocol - use timeout to detect packet
loss and congestions
• TCP-reno (Jacobson, 1990)
– Triple-ACK and time-out based - Use triple-duplicate
ACK to same sequence number and timeouts to detect
packet loss and congestions
– Use fast retransmissions and fast recovery
• Skip Slow Start phase
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP-tahoe Protocol
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP-reno Protocol
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
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ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP protocol control variable
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Bandwidth: m in packets/sec,
Service time: 1/m
Round Trip Time (RTT): T sec
Buffer size: B in packets
Path pipeline capacity:
Wpipe = m*T+B+1
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Layers: 5-Layer Protocol Model
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1) Physical layer
2) Network access layer
3) Internet layer
4) Host-to-host, or transport layer
5) Application layer
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Physical Layer
• Covers the physical interface between a
data transmission device and a
transmission medium or network
• Physical layer specifies:
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Characteristics of the transmission medium
The nature of the signals
The data rate
Other related matters
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Network Access Layer
• Concerned with the exchange of data
between an end system and the network to
which it's attached
• Software used depends on type of network
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Circuit switching
Packet switching (e.g., X.25)
LANs (e.g., Ethernet)
Others
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Internet Layer
• Uses internet protocol (IP)
• Provides routing functions to allow data to
traverse multiple interconnected networks
• Implemented in end systems and routers
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Host-to-Host, or
Transport Layer
• Commonly uses transmission control
protocol (TCP)
• Provides reliability during data exchange
– Completeness
– Order
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP/IP Application Layer
• Logic supports user applications
• Uses separate modules that are peculiar to
each different type of application
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Protocol Data Units (PDUs)
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
TCP Header Format
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
IP Header Format-1: IPv4 Header
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
IP Header Format-2: IPv6 Header (Newer
Version since 1995)
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Common TCP/IP Applications
• Simple mail transfer protocol (SMTP)
– Provides a basic electronic mail facility
• File Transfer Protocol (FTP)
– Allows files to be sent from one system to
another
• TELNET
– Provides a remote logon capability
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Service Access Point (SAP) under TCP/IP
Concepts
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Internetworking Terms
• Communication network – facility that provides a data
transfer service among devices attached to the network
• Internet – collection of communication networks,
interconnected by bridges/routers
• Intranet – internet used by an organization for internal
purposes
– Provides key Internet applications
– Can exist as an isolated, self-contained internet
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Internetworking Terms
• End System (ES) – device used to support
end-user applications or services
• Intermediate System (IS) – device used to
connect two networks
• Bridge – an IS used to connect two LANs
that use similar LAN protocols
• Router - an IS used to connect two networks
that may or may not be similar (such as
WAN and LAN)
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Functions of a Router
• Provide a link between networks
• Provide for the routing and delivery of data
between processes on end systems attached
to different networks
• Provide these functions in such a way as not
to require modifications of the networking
architecture of any of the attached subnetworks
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
An Example of Router Applications
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang
Network Differences Routers
Must Accommodate
• Addressing schemes
– Different schemes for assigning addresses
• Maximum packet sizes
– Different maximum packet sizes requires segmentation
• Interfaces
– Differing hardware and software interfaces
• Reliability
– Network may provide unreliable service
ECEN 619, Internet Protocols & Modeling
Prof. Xi Zhang