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ECEN 619-600 “Internet Protocols and Modeling”
Course Materials: Papers, Reference Texts: Bertsekas/Gallager, Stuber, Stallings, etcGrading (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 ZhangE-mail: xizhang@ece.tamu.edu
Office: WERC 331
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP Closed-loop flow control and “Self-Clocking” Principle-1
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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 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.
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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.
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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.
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP-tahoe Protocol
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP-reno Protocol
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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TCP protocol control variable
• Bandwidth: mm 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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP/IP Host-to-Host, or Transport Layer
• Commonly uses transmission control protocol (TCP)
• Provides reliability during data exchange– Completeness– Order
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP/IP Application Layer
• Logic supports user applications
• Uses separate modules that are peculiar to each different type of application
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
Protocol Data Units (PDUs)
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
TCP Header Format
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
IP Header Format-1: IPv4 Header
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
IP Header Format-2: IPv6 Header (Newer Version since 1995)
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
Service Access Point (SAP) under TCP/IP Concepts
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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)
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
An Example of Router Applications
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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
Prof. Xi ZhangECEN 619, Internet Protocols & Modeling
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