ECEN 619-600

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ECEN 619-600 Internet Protocols and Modeling

• Course Materials Papers, Reference Texts
  Bertsekas/Gallager, Stuber, Stallings, etc
• Grading (Tentative) HW 20, Projects 40,
  Exam-120, Exam-II20
• Lecture notes and Paper Reading Lists available
  on-line TBA
• Class Website http//ece.tamu.edu/xizhang/ECEN61
  9/start.php
• Research Interests and Projects
  URLhttp//ece.tamu.edu/xizhang
• Instructor Professor Xi Zhang
• E-mail xizhang_at_ece.tamu.edu
• Office WERC 331

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TCP Closed-loop flow control and Self-Clocking
Principle-1
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TCP Closed-loop flow control and Self-Clocking
Principle-2

• 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 doesnt change as a packet
  goes through the network so a packet squeezed
  into the smaller long-haul bandwidth must spread
  out in time.

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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 receivers net packet spacing
  Pr Pb.
• If the receiver processing time is the same for
  all packets, the spacing between ACKs on the
  receivers net Ar Pr Pb.

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TCP Closed-loop flow control and Self-Clocking
Principle

• If the time slot Pb was big enough for a packet,
  its big enough for an ACK so the ACK spacing is
  preserved along the return path. Thus the ACK
  spacing on the senders net As Pb.
• So, if packets after the first burst are sent
  only in response to an ACK, the senders packet
  spacing will be exactly match the packet time on
  the slowest link in the path gt Self-Clocking
  is achieved.

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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

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TCP-tahoe Protocol
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TCP-reno Protocol
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TCP protocol control variable

• Bandwidth m in packets/sec,
• Service time 1/m
• Round Trip Time (RTT) T sec
• Buffer size B in packets
• Path pipeline capacity
• Wpipe mTB1

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TCP/IP Layers 5-Layer Protocol Model

• 1) Physical layer
• 2) Network access layer
• 3) Internet layer
• 4) Host-to-host, or transport layer
• 5) Application layer

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TCP/IP Physical Layer

• Covers the physical interface between a data
  transmission device and atransmission medium or
  network
• Physical layer specifies
• Characteristics of the transmission medium
• The nature of the signals
• The data rate
• Other related matters

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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
• Circuit switching
• Packet switching (e.g., X.25)
• LANs (e.g., Ethernet)
• Others

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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

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TCP/IP Host-to-Host, or Transport Layer

• Commonly uses transmission control protocol (TCP)
• Provides reliability during data exchange
• Completeness
• Order

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TCP/IP Application Layer

• Logic supports user applications
• Uses separate modules that are peculiar to each
  different type of application

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Protocol Data Units (PDUs)
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TCP Header Format
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IP Header Format-1 IPv4 Header
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IP Header Format-2 IPv6 Header (Newer Version
since 1995)
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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

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Service Access Point (SAP) under TCP/IP Concepts
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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

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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)

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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 sub-networks

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An Example of Router Applications
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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