ECEN 619-600 “Internet Protocols and Modeling” Course Materials: Papers, Reference Texts:...

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: [email protected]

Office: WERC 331

Prof. Xi ZhangECEN 619, Internet Protocols & Modeling

TCP Closed-loop flow control and “Self-Clocking” Principle-1



• 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.



• 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.


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.


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


TCP-tahoe Protocol


TCP-reno Protocol



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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


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


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


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


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


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

• Commonly uses transmission control protocol (TCP)

• Provides reliability during data exchange– Completeness– Order


TCP/IP Application Layer

• Logic supports user applications

• Uses separate modules that are peculiar to each different type of application


Protocol Data Units (PDUs)


TCP Header Format


IP Header Format-1: IPv4 Header


IP Header Format-2: IPv6 Header (Newer Version since 1995)


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


Service Access Point (SAP) under TCP/IP Concepts


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


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)


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


An Example of Router Applications


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


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ECEN 619-600 “Internet Protocols and Modeling” Course Materials: Papers, Reference Texts:...

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