# Answer to the written exam given on TDTS06 Computer networks, October 23,

Save this PDF as:

Size: px
Start display at page:

Download "Answer to the written exam given on TDTS06 Computer networks, October 23,"

## Transcription

1 Answer to the written exam given on TDTS06 Computer networks, October 23, Answers provided by Juha Takkinen, IDA, Question 1. Protocol = a set of rules for what messages to send (syntax), in what order (timing), and what they mean (semantics). Network architecture = an architecture for how to organize protocols that provide network functionality to an application, usually consisting of layers, where a layer provides services to the layer above it. (Reference model for network architectures = standardized network architecture, for example the OSI model with seven layers or the Internet model with four layers) (Network design = how to organize the network equipment, such as computers, hubs, switches, and routers, so that it fulfills the performance requirements of the network users and applications) The sender has 4 states (two for each sequence number, of whch one is for DATA and the other one for ACK) while the receiver has 2 states (one for each sequence number). The receiver does nothing when a packet is lost; it just ACKs all packets that are received. Question 2. [the question does not have any part] Assume no other delays than those stated (RTT) and headers included in calculations. Also assume that the ACK has no transmission time, only propagation. i) The total transfer time = (handshake time) + (transfer of packet A--R1) + (transfer of fragments R1--B) + (transfer of ACK B--A) = = (2 x RTT) + ( (1000 x 8 x 10^3) / (5 x 10^6) ) + (2 x (250 x 8 x 10^3) / (5 x 10^6) + 3 x (250 x 8 x 10^3) / (5 x 10^6) ) + (RTT / 2) = = 0.2 s s + 2 s s = 3.85 s. (note that the routers are performing work in parallell when data is divided into packets) ii)

2 The average throughput = data amount / total transfer time = (1000 x 8 x 10^3) / 3.85 bps = 2078 x 10^3 bps = 260 KB/s The sender will move its window only one step to the right, covering positions 1-5, when it receives the four remaining ACKs because of the missing ACK for packet no. 1. The retransmission timers for the other packets till be stopped. The retransmission timer for packet 1 will count down and then the packet till be retransmitted by the sender. The receiver will retransmit the ACK for packet 1. When the ACK for packet 1 is received by the sender, the sender can move the window to positions Question 3. [For clarity s sake, the whole session is given below, with the lines from the question inserted with their number] telnet smtp.liu.se 25 Trying Connected to smtp.liu.se. Escape character is ^]. ix) 220 munin.unit.liu.se ESMTP Postfix [the smtp server presents itself and the protocol version] ii) helo liu.se [the smtp client and its domain present itself to the server] x) 250 munin.unit.liu.se [the server acknowledges the helo command] viii) mail [the client lists the sender] x) 250 Ok [the server acknowledges the mail command] v) rcpt [the client lists the receiver] x) 250 Ok i) data [start of data] 354 End data with <CR><LF>.<CR><LF> iii) mime-version: 1.0 [the message will be encoded using mime so that more than 7-bit ascii can be accommodated, if any] vii)happy holidays! [the message] iv). [period] [the message is finished and will now be sent] x) 250 Ok: queued as AA756279A9F vi) quit [quit the session; no more s from this domain] 221 Bye Connection to smtp.liu.se closed by foreign host.

3 % The DHT data structure is commonly used as an index for storing and looking up information about hosts and what data they have stored. Data is stored as <key, value> pairs in the nodes of the DHT. The key in the data pair is, for example, the name of the music file to be searched, and the value is the ip address of the host that has the mp3 file in question. Both the node ID and the data key are hashed using the same hash function. In this way a simple match can be performed on the data key and the node ID in order to locate the node that has the key and subsequently look up the value (ip address). The root server knows about TLD servers, while the authoritative server knows about hosts owned by the organization where the authoritative server is situated, including mail drops, if any. Question 4. The timeout value is based on the samplertt, estimatedrtt and devrtt and three different constants, all calculated using the exponential moving weighted average. [a list of the relevant formulas follows] single ACK = transmit the next segment in the sending window, which has the exact sequence number of the ACK double ACK = update the counter for duplicate ACKs triple duplicate ACK = reset the counter for duplicate ACKs and go to fast retransmit of the lost segment with the same sequence number as the ACK. Then, halve the sending rate by setting the congestion window to half of its value and the threshold to this halved value. Question 5. Ip packets can get lost, i.e., dropped in a router because they have the wrong checksum or the outgoing queue is full (another reason can be that the TTL field has reached zero). When an ip packet is fragmented each fragment is sent as an individual ip packet. They are reassembled at the receiver, based on the information stored in the second word in the packet header: the ID field has the same value for every fragment that belong to the

5 The sender reserves the channel by sending an RTS to the receiver. The receiver responds with a CTS, which is heard by all stations within range of the receiver and which are also hidden from the sender. Then the sender can transmit its data, after which the receiver concludes with an ACK. The ACK is also heard by the hidden stations, which now are free to try and access the channel. Question 7. [the algorithm actually builds the routing table, which in turn is used to derived the forwarding table] N B C D E F A 1, A AB done 2, B ABC done done 3, C - - ABCD done done done 4, D 10, D ABCDE done done done done 5, E ABCDEF done done done done done The forwarding table in A consists of columns for destination, nexthop and cost as follows: A - - B B 1 C B 2 D B 3 E B 4 F B 5 The inter-as protocol is concerned only with reachability and implements an organization s policy about its network s visibility to the outside world, what and how much traffic from other companies to carry, etc. The BGP protocol implements this. The intra-as protocol is concerned with least-cost paths and varying requirements connected to different-sized organizations. Therefore, several routing protocols are available here, such as RIP, OSPF and others by Cisco for example. The interplay between the two types of protocols listed above is based on distributing varying information to all routers within ASs about which outside networks (foreign ASs) that are reachable from each AS and where a next-hop foreign router is along a path of ASs. Routing loops is a problem that can occur in routing protocols, which means that the

6 same node occurs more than once along a path. Question 8. The handshake is needed because SSL must negotiate several security protocols (for encryption and hashing) before data can be transferred. Also, the communicating nodes must authenticate themselves, at the same time preventing insertion and playback attacks by using nonces and MACs. The operations are true because the message m is encrypted. This is accomplished using a shared secret key (session key, Ks) randomly created by the sender. In order for the receiver to be able to decrypt the confidential message, the session key is appended (+) to the sent message and encrypted using the public key of the receiver (Kb+). Authentication in WEP is done using a shared secret key. A nonce is encrypted with this key in order to prevent playback attacks. This action is performed by both the wireless station and the access point.

### II. Principles of Computer Communications Network and Transport Layer

II. Principles of Computer Communications Network and Transport Layer A. Internet Protocol (IP) IPv4 Header An IP datagram consists of a header part and a text part. The header has a 20-byte fixed part

### CSE 473 Introduction to Computer Networks. Final Exam. Your name here: 12/17/2012

CSE 473 Introduction to Computer Networks Jon Turner Final Exam Your name here: 12/17/2012 1. (8 points). The figure below shows a network path connecting a server to a client. 200 km 2000 km 2 km X Y

### Networking: Network layer

control Networking: Network layer Comp Sci 3600 Security Outline control 1 2 control 3 4 5 Network layer control Outline control 1 2 control 3 4 5 Network layer purpose: control Role of the network layer

### Student ID: CS457: Computer Networking Date: 5/8/2007 Name:

CS457: Computer Networking Date: 5/8/2007 Name: Instructions: 1. Be sure that you have 10 questions 2. Write your Student ID (email) at the top of every page 3. Be sure to complete the honor statement

### Chapter 2 - Part 1. The TCP/IP Protocol: The Language of the Internet

Chapter 2 - Part 1 The TCP/IP Protocol: The Language of the Internet Protocols A protocol is a language or set of rules that two or more computers use to communicate 2 Protocol Analogy: Phone Call Parties

### Closed book. Closed notes. No electronic device.

414-S17 (Shankar) Exam 3 PRACTICE PROBLEMS Page 1/6 Closed book. Closed notes. No electronic device. 1. Anonymity Sender k-anonymity Receiver k-anonymity Authoritative nameserver Autonomous system BGP

### TCP /IP Fundamentals Mr. Cantu

TCP /IP Fundamentals Mr. Cantu OSI Model and TCP/IP Model Comparison TCP / IP Protocols (Application Layer) The TCP/IP subprotocols listed in this layer are services that support a number of network functions:

### No, the bogus packet will fail the integrity check (which uses a shared MAC key).!

1. High level questions a. Suppose Alice and Bob are communicating over an SSL session. Suppose an attacker, who does not have any of the shared keys, inserts a bogus TCP segment into a packet stream with

### CSCI Networking Name:

CSCI 3335- Networking Name: Final Exam Problem 1: Error Checking and TCP (15 Points) (a) True or false: [2.5 points for circling correct answers, -1 points for each wrong answer] i. CRC can both correct

### Introduction to Open System Interconnection Reference Model

Chapter 5 Introduction to OSI Reference Model 1 Chapter 5 Introduction to Open System Interconnection Reference Model Introduction The Open Systems Interconnection (OSI) model is a reference tool for understanding

### ECSE 414 Fall 2014 Final Exam Solutions

ECSE 414 Fall 2014 Final Exam Solutions Question 1 a. The five main layers of the internet protocol stack, along with the service provided by each, and the place where each is implemented are as follows:

### cs/ee 143 Communication Networks

cs/ee 143 Communication Networks Chapter 4 Transport Text: Walrand & Parakh, 2010 Steven Low CMS, EE, Caltech Recap: Internet overview Some basic mechanisms n Packet switching n Addressing n Routing o

### Peer entities. Protocol Layering. Protocols. Example

Peer entities Protocol Layering An Engineering Approach to Computer Networking Customer A and B are peers Postal worker A and B are peers Protocols A protocol is a set of rules and formats that govern

### Flow and Congestion Control (Hosts)

Flow and Congestion Control (Hosts) 14-740: Fundamentals of Computer Networks Bill Nace Material from Computer Networking: A Top Down Approach, 6 th edition. J.F. Kurose and K.W. Ross traceroute Flow Control

### UDP and TCP. Introduction. So far we have studied some data link layer protocols such as PPP which are responsible for getting data

ELEX 4550 : Wide Area Networks 2015 Winter Session UDP and TCP is lecture describes the two most common transport-layer protocols used by IP networks: the User Datagram Protocol (UDP) and the Transmission

### Top-Down Network Design, Ch. 7: Selecting Switching and Routing Protocols. Top-Down Network Design. Selecting Switching and Routing Protocols

Top-Down Network Design Chapter Seven Selecting Switching and Routing Protocols Copyright 2010 Cisco Press & Priscilla Oppenheimer 1 Switching 2 Page 1 Objectives MAC address table Describe the features

### Wireless Security Protocol Analysis and Design. Artoré & Bizollon : Wireless Security Protocol Analysis and Design

Protocol Analysis and Design 1 Networks 1. WIRELESS NETWORKS 2 Networks 1. WIRELESS NETWORKS 1.1 WiFi 802.11 3 Networks OSI Structure 4 Networks Infrastructure Networks BSS : Basic Set Service ESS : Extended

### Outline. Routing. Introduction to Wide Area Routing. Classification of Routing Algorithms. Introduction. Broadcasting and Multicasting

Outline Routing Fundamentals of Computer Networks Guevara Noubir Introduction Broadcasting and Multicasting Shortest Path Unicast Routing Link Weights and Stability F2003, CSG150 Fundamentals of Computer

### CS519: Computer Networks. Lecture 5, Part 4: Mar 29, 2004 Transport: TCP congestion control

: Computer Networks Lecture 5, Part 4: Mar 29, 2004 Transport: TCP congestion control TCP performance We ve seen how TCP the protocol works Sequencing, receive window, connection setup and teardown And

### Final Exam for ECE374 05/03/12 Solution!!

ECE374: Second Midterm 1 Final Exam for ECE374 05/03/12 Solution!! Instructions: Put your name and student number on each sheet of paper! The exam is closed book. You have 90 minutes to complete the exam.

### CS 458 Internet Engineering Spring First Exam

CS 458 Internet Engineering Spring 2005 First Exam Instructions (read carefully): There are 6 problems for a total of 60 points. This is a closed book and closed notes in-class exam. If any problem is

### TDTS06: Computer Networks

TDTS06: Computer Networks Instructor: Niklas Carlsson Email: niklas.carlsson@liu.se Notes derived from Computer Networking: A Top Down Approach, by Jim Kurose and Keith Ross, Addison-Wesley. The slides

### Lab 9.8.1: Address Resolution Protocol (ARP)

Topology Diagram Addressing Table Device Interface IP Address Subnet Mask Default Gateway R1-ISP R2-Central S0/0/0 10.10.10.6 255.255.255.252 N/A Fa0/0 192.168.254.253 255.255.255.0 N/A S0/0/0 10.10.10.5

### Network: infrastructure (hard/software) that enables endpoints (hosts) to communicate

221 7 (Inter)Networking Network: infrastructure (hard/software) that enables endpoints (hosts) to communicate Internetwork: system of two or more networks (segments), connected via gateways, which enables

### Lecture 33. Firewalls. Firewall Locations in the Network. Castle and Moat Analogy. Firewall Types. Firewall: Illustration. Security April 15, 2005

Firewalls Lecture 33 Security April 15, 2005 Idea: separate local network from the Internet Trusted hosts and networks Intranet Firewall DMZ Router Demilitarized Zone: publicly accessible servers and networks

### Chapter -4 OSI Reference Model

Chapter -4 OSI Reference Model Objectives Concept of Reference Model. OSI Reference Model Concept. Layers of OSI Reference Model. 4.1 Introduction Layered Architecture, Peer-to- Peer Processes, Interfaces

### Lecture 4: Congestion Control

Lecture 4: Congestion Control Overview Internet is a network of networks Narrow waist of IP: unreliable, best-effort datagram delivery Packet forwarding: input port to output port Routing protocols: computing

### Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice

Hierarchical Routing Our routing study thus far - idealization all routers identical network flat not true in practice scale: with 200 million destinations: can t store all destinations in routing tables!

### Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice

Hierarchical Routing Our routing study thus far - idealization all routers identical network flat not true in practice scale: with 200 million destinations: can t store all destinations in routing tables!

### User Datagram Protocol (UDP):

SFWR 4C03: Computer Networks and Computer Security Feb 2-5 2004 Lecturer: Kartik Krishnan Lectures 13-15 User Datagram Protocol (UDP): UDP is a connectionless transport layer protocol: each output operation

### Fundamentals of Networking. OSI & TCP/IP Model. Kuldeep Sonar 1

Fundamentals of Networking OSI & TCP/IP Model Kuldeep Sonar 1 Kuldeep Sonar 2 OSI Model Kuldeep Sonar 3 Application Layer Layer 7 provides an interface between a host s communication software and any necessary

### CISCO EXAM QUESTIONS & ANSWERS

CISCO 100-101 EXAM QUESTIONS & ANSWERS Number: 100-101 Passing Score: 800 Time Limit: 120 min File Version: 35.5 http://www.gratisexam.com/ CISCO 100-101 EXAM QUESTIONS & ANSWERS Exam Name: CCNA Interconnecting

### MID-TERM EXAM TCP/IP NETWORKING Duration: 2 hours With Solutions

MID-TERM EXAM TCP/IP NETWORKING Duration: 2 hours With Solutions Jean-Yves Le Boudec 2005 December 8 Do not forget to put your names on all sheets of your solution. If you need to make assumptions in order

### Mobile Communications. Ad-hoc and Mesh Networks

Ad-hoc+mesh-net 1 Mobile Communications Ad-hoc and Mesh Networks Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto Ad-hoc+mesh-net 2 What is an ad-hoc network? What are differences between

### Wireless LANs. ITS 413 Internet Technologies and Applications

Wireless LANs ITS 413 Internet Technologies and Applications Aim: Aim and Contents Understand how IEEE 802.11 wireless LANs work Understand what influences the performance of wireless LANs Contents: IEEE

### Review for Chapter 4 R1,R2,R3,R7,R10,R11,R16,R17,R19,R22,R24, R26,R30 P1,P2,P4,P7,P10,P11,P12,P14,P15,P16,P17,P22,P24,P29,P30

Review for Chapter 4 R1,R2,R3,R7,R10,R11,R16,R17,R19,R22,R24, R26,R30 P1,P2,P4,P7,P10,P11,P12,P14,P15,P16,P17,P22,P24,P29,P30 R1. Let s review some of the terminology used in this textbook. Recall that

### Question Points Score total 100

CS457: Computer Networking Date: 3/21/2008 Name: Instructions: 1. Be sure that you have 8 questions 2. Be sure your answers are legible. 3. Write your Student ID at the top of every page 4. This is a closed

### CIT 380: Securing Computer Systems. Network Security Concepts

CIT 380: Securing Computer Systems Network Security Concepts Topics 1. Protocols and Layers 2. Layer 2 Network Concepts 3. MAC Spoofing 4. ARP 5. ARP Spoofing 6. Network Sniffing Protocols A protocol defines

### IS370 Data Communications and Computer Networks. Chapter 5 : Transport Layer

IS370 Data Communications and Computer Networks Chapter 5 : Transport Layer Instructor : Mr Mourad Benchikh Introduction Transport layer is responsible on process-to-process delivery of the entire message.

### CSCI 466 Midterm Networks Fall 2013

CSCI 466 Midterm Networks Fall 2013 Name: This exam consists of 6 problems on the following 7 pages. You may use your single-sided hand-written 8 ½ x 11 note sheet and a calculator during the exam. No

### Debian/GNU Linux Networking

Debian/GNU Linux Networking Basics of the Networking Károly Erdei October 15, 2014 Károly Erdei Debian/GNU Linux Networking 1/41 Agenda 1 Networks 2 Ethernet 3 Internet Protocol 4 TCP 5 DHCP 6 Check Network

### Network Layer. The Network Layer. Contents Connection-Oriented and Connectionless Service. Recall:

Network Layer The Network Layer Recall: The network layer is responsible for the routing of packets The network layer is responsible for congestion control 1 2 Contents 4.1.1 Connection-Oriented and Connectionless

### Routing Protocols. Autonomous System (AS)

Routing Protocols Two classes of protocols: 1. Interior Routing Information Protocol (RIP) Open Shortest Path First (OSPF) 2. Exterior Border Gateway Protocol (BGP) Autonomous System (AS) What is an AS?

### Overview. Problem: Find lowest cost path between two nodes Factors static: topology dynamic: load

Dynamic Routing Overview Forwarding vs Routing forwarding: to select an output port based on destination address and routing table routing: process by which routing table is built Network as a Graph C

### Routing Overview. Information About Routing CHAPTER

21 CHAPTER This chapter describes underlying concepts of how routing behaves within the ASA, and the routing protocols that are supported. This chapter includes the following sections: Information About

### CMPE150 Midterm Solutions

CMPE150 Midterm Solutions Question 1 Packet switching and circuit switching: (a) Is the Internet a packet switching or circuit switching network? Justify your answer. The Internet is a packet switching

### CHAPTER 18 INTERNET PROTOCOLS ANSWERS TO QUESTIONS

CHAPTER 18 INTERNET PROTOCOLS ANSWERS TO QUESTIONS 18.1 (1) The communications network may only accept blocks of data up to a certain size. (2) Error control may be more efficient with a smaller PDU size.

### Problem Set 7 Due: Start of Class, November 2

CS242 Computer Networks Handout # 14 Randy Shull October 26, 2017 Wellesley College Problem Set 7 Due: Start of Class, November 2 Reading: Kurose & Ross, Sections 3.6, 3.7, 3.8 Wireshark Lab [26] In these

### Congestion Control In The Internet Part 2: How it is implemented in TCP. JY Le Boudec 2014

1 Congestion Control In The Internet Part 2: How it is implemented in TCP JY Le Boudec 2014 Contents 1. Congestion control in TCP 2. The fairness of TCP 3. The loss throughput formula 4. Explicit Congestion

### Internetworking Part 2

CMPE 344 Computer Networks Spring 2012 Internetworking Part 2 Reading: Peterson and Davie, 3.2, 4.1 19/04/2012 1 Aim and Problems Aim: Build networks connecting millions of users around the globe spanning

### Administrivia CSC458 Lecture 4 Bridging LANs and IP. Last Time. This Time -- Switching (a.k.a. Bridging)

Administrivia CSC458 Lecture 4 Bridging LANs and IP Homework: # 1 due today # 2 out today and due in two weeks Readings: Chapters 3 and 4 Project: # 2 due next week Tutorial today: Joe Lim on project 2

### Direct Link Communication I: Basic Techniques. Data Transmission. ignore carrier frequency, coding etc.

Direct Link Communication I: Basic Techniques Link speed unit: bps abstraction Data Transmission ignore carrier frequency, coding etc. Point-to-point link: wired or wireless includes broadcast case Interested

### TRANSMISSION CONTROL PROTOCOL

COMP 635: WIRELESS NETWORKS TRANSMISSION CONTROL PROTOCOL Jasleen Kaur Fall 2015 1 Impact of Wireless on Protocol Layers Application layer Transport layer Network layer Data layer Physical layer service

### Lab 2.8.1: Basic Static Route Configuration

Topology Diagram Addressing Table Device Interface IP Address Subnet Mask Default Gateway R1 Fa0/0 172.16.3.1 255.255.255.0 N/A S0/0/0 172.16.2.1 255.255.255.0 N/A Fa0/0 172.16.1.1 255.255.255.0 N/A R2

### Mobile Communications Chapter 9: Network Protocols/Mobile IP

Mobile Communications Chapter 9: Network Protocols/Mobile IP Motivation Data transfer Encapsulation Security IPv6 Problems DHCP Ad-hoc s Routing protocols 9.0.1 Motivation for Mobile IP Routing based on

### Chapter 7 Internet Protocol Version 4 (IPv4) Kyung Hee University

Chapter 7 Internet Protocol Version 4 (IPv4) 1 7.1 Introduction The transmission mechanism used by the TCP/IP Unreliable and connectionless datagram protocol Best-effort delivery service IP packets can

### TCP Congestion Control

TCP Congestion Control Lecture material taken from Computer Networks A Systems Approach, Third Ed.,Peterson and Davie, Morgan Kaufmann, 2003. Computer Networks: TCP Congestion Control 1 TCP Congestion

### Mobile IP. rek. Petr Grygárek Petr Grygarek, Advanced Computer Networks Technologies 1

Mobile IP Petr Grygárek rek 1 Basic principle Picture from IOS IP and IP Routing Configuration Guide Mobile node maintains the same IP address even while roaming in foreign networks even if it s address

### Introduction to Networks and the Internet

Introduction to Networks and the Internet CMPE 80N Announcements Project 2. Reference page. Library presentation. Internet History video. Spring 2003 Week 7 1 2 Today Internetworking (cont d). Fragmentation.

### CSC 574 Computer and Network Security. TCP/IP Security

CSC 574 Computer and Network Security TCP/IP Security Alexandros Kapravelos kapravelos@ncsu.edu (Derived from slides by Will Enck and Micah Sherr) Network Stack, yet again Application Transport Network

### ECE4110, Internetwork Programming, QUIZ 2 - PRACTICE Spring 2006

Email Address ECE4110, Internetwork Programming, QUIZ 2 - PRACTICE Spring 2006 Name (Print) Prof. John A. Copeland Practice for April 11, 2006 Tel.: 404-894-5177 E-Mail: copeland@ece.gatech.edu RULES.

### Medium Access Control Sublayer

Wireless (WLAN) Medium Access Control Sublayer Mahalingam Mississippi State University, MS October 20, 2014 Outline Medium Access Protocols Wireless (WLAN) 1 Medium Access Protocols ALOHA Slotted ALOHA

### ECE 4450:427/527 - Computer Networks Spring 2017

ECE 4450:427/527 - Computer Networks Spring 2017 Dr. Nghi Tran Department of Electrical & Computer Engineering Lecture 6.2: IP Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527 Computer Networks

### COMP211 Chapter 4 Network Layer: The Data Plane

COMP211 Chapter 4 Network Layer: The Data Plane All material copyright 1996-2016 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 7 th edition Jim Kurose, Keith Ross

### Fast Retransmit. Problem: coarsegrain. timeouts lead to idle periods Fast retransmit: use duplicate ACKs to trigger retransmission

Fast Retransmit Problem: coarsegrain TCP timeouts lead to idle periods Fast retransmit: use duplicate ACKs to trigger retransmission Packet 1 Packet 2 Packet 3 Packet 4 Packet 5 Packet 6 Sender Receiver

### Congestion Control In The Internet Part 2: How it is implemented in TCP. JY Le Boudec 2015

1 Congestion Control In The Internet Part 2: How it is implemented in TCP JY Le Boudec 2015 Contents 1. Congestion control in TCP 2. The fairness of TCP 3. The loss throughput formula 4. Explicit Congestion

### Lecture 2: Basic routing, ARP, and basic IP

Internetworking Lecture 2: Basic routing, ARP, and basic IP Literature: Forouzan, TCP/IP Protocol Suite: Ch 6-8 Basic Routing Delivery, Forwarding, and Routing of IP packets Connection-oriented vs Connectionless

### TCP Service Model. Today s Lecture. TCP Support for Reliable Delivery. EE 122:TCP, Connection Setup, Reliability

Today s Lecture How does TCP achieve correct operation? EE 122:TCP, Connection Setup, Reliability Ion Stoica TAs: Junda Liu, DK Moon, David Zats Reliability in the face of IP s best effort service 3-way

### Mobile Communications Chapter 9: Mobile Transport Layer

Prof. Dr.-Ing Jochen H. Schiller Inst. of Computer Science Freie Universität Berlin Germany Mobile Communications Chapter 9: Mobile Transport Layer Motivation, TCP-mechanisms Classical approaches (Indirect

### ECSE-6600: Internet Protocols Spring 2007, Exam 1 SOLUTIONS

ECSE-6600: Internet Protocols Spring 2007, Exam 1 SOLUTIONS Time: 75 min (strictly enforced) Points: 50 YOUR NAME (1 pt): Be brief, but DO NOT omit necessary detail {Note: Simply copying text directly

### Review of Internet Architecture and Protocols

Review of Internet Architecture and Protocols Professor Guevara Noubir Northeastern University noubir@ccs.neu.edu Lecture Reference Textbook: (source of some diagrams) Computer Networks: A Systems Approach,

### Last time. Network layer. Introduction. Virtual circuit vs. datagram details. IP: the Internet Protocol. forwarding vs. routing

Last time Network layer Introduction forwarding vs. routing Virtual circuit vs. datagram details connection setup, teardown VC# switching forwarding tables, longest prefix matching IP: the Internet Protocol

### Computer Networks. Wenzhong Li. Nanjing University

Computer Networks Wenzhong Li Nanjing University 1 Chapter 2. Direct Link Networks Link Service and Framing Error Detection and Reliable Transmission HDLC, PPP, and SONET Token Ring Ethernet Bridges and

### OSI Reference Model. Computer Networks lab ECOM Prepared By : Eng. Motaz Murtaja Eng. Ola Abd Elatief

Islamic University of Gaza Faculty of Engineering Computer Engineering Department Computer Networks lab ECOM 4121 OSI Reference Model Prepared By : Eng. Motaz Murtaja Eng. Ola Abd Elatief May /2010 OSI

### 10 minutes survey (anonymous)

10 minutes survey (anonymous) v Comments/Suggestions to my lecture/lab/ homework/exam v If you like this course, which part do you like? v If you don t like it, which part do you not like? Thanks! Transport

### Flow and Congestion Control

CE443 Computer Networks Flow and Congestion Control Behnam Momeni Computer Engineering Department Sharif University of Technology Acknowledgments: Lecture slides are from Computer networks course thought

### shortcut Tap into learning NOW! Visit for a complete list of Short Cuts. Your Short Cut to Knowledge

shortcut Your Short Cut to Knowledge The following is an excerpt from a Short Cut published by one of the Pearson Education imprints. Short Cuts are short, concise, PDF documents designed specifically

### Introduction to Routers and LAN Switches

Introduction to Routers and LAN Switches Session 3048_05_2001_c1 2001, Cisco Systems, Inc. All rights reserved. 3 Prerequisites OSI Model Networking Fundamentals 3048_05_2001_c1 2001, Cisco Systems, Inc.

### Ethernet Hub. Campus Network Design. Hubs. Sending and receiving Ethernet frames via a hub

Campus Network Design Thana Hongsuwan Ethernet Hub 2003, Cisco Systems, Inc. All rights reserved. 1-1 2003, Cisco Systems, Inc. All rights reserved. BCMSN v2.0 1-2 Sending and receiving Ethernet frames

### THE INTERNET PROTOCOL/1

THE INTERNET PROTOCOL a (connectionless) network layer protocol designed for use in interconnected systems of packet-switched computer communication networks (store-and-forward paradigm) provides for transmitting

### To make a difference between logical address (IP address), which is used at the network layer, and physical address (MAC address),which is used at

To make a difference between logical address (IP address), which is used at the network layer, and physical address (MAC address),which is used at the data link layer. To describe how the mapping of a

### Lecture 4 - Network Layer. Transport Layer. Outline. Introduction. Notes. Notes. Notes. Notes. Networks and Security. Jacob Aae Mikkelsen

Lecture 4 - Network Layer Networks and Security Jacob Aae Mikkelsen IMADA September 23, 2013 September 23, 2013 1 / 67 Transport Layer Goals understand principles behind network layer services: network

### Growth. Individual departments in a university buy LANs for their own machines and eventually want to interconnect with other campus LANs.

Internetworking Multiple networks are a fact of life: Growth. Individual departments in a university buy LANs for their own machines and eventually want to interconnect with other campus LANs. Fault isolation,

### CSC 401 Data and Computer Communications Networks

CSC 401 Data and Computer Communications Networks Transport Layer Connection Oriented Transport: TCP Sec 3.5 Prof. Lina Battestilli Fall 2017 Transport Layer Chapter 3 Outline 3.1 Transport-layer Services

### Distributed Queue Dual Bus

Distributed Queue Dual Bus IEEE 802.3 to 802.5 protocols are only suited for small LANs. They cannot be used for very large but non-wide area networks. IEEE 802.6 DQDB is designed for MANs It can cover

### Extending or Interconnecting LANS. Physical LAN segment. Virtual LAN. Forwarding Algorithm 11/9/15. segments. VLAN2, Port3. VLAN1, Port1.

Physical LAN segment q Hosts connected on the same physical LAN segment q Same subnet; L2 forwarding q ARP (IPè MAC) L2 frame (S, D), send q Scale? Extending or Interconnecting LANS q q q Why not just

### Internet Protocol and Transmission Control Protocol

Internet Protocol and Transmission Control Protocol CMSC 414 November 13, 2017 Internet Protcol Recall: 4-bit version 4-bit hdr len 8-bit type of service 16-bit total length (bytes) 8-bit TTL 16-bit identification

### Exercise Sheet 4. Exercise 1 (Routers, Layer-3-Switches, Gateways)

Exercise Sheet 4 Exercise 1 (Routers, Layer-3-Switches, Gateways) 1. What is the purpose of Routers in computer networks? (Also explain the difference to Layer-3-Switches.) 2. What is the purpose of Layer-3-Switches

### Unit 2.

Unit 2 Unit 2 Topics Covered: 1. PROCESS-TO-PROCESS DELIVERY 1. Client-Server 2. Addressing 2. IANA Ranges 3. Socket Addresses 4. Multiplexing and Demultiplexing 5. Connectionless Versus Connection-Oriented

### Manual Key Configuration for Two SonicWALLs

Manual Key Configuration for Two SonicWALLs VPN between two SonicWALLs allows users to securely access files and applications at remote locations. The first step to set up a VPN between two SonicWALLs

### Layer 4: UDP, TCP, and others. based on Chapter 9 of CompTIA Network+ Exam Guide, 4th ed., Mike Meyers

Layer 4: UDP, TCP, and others based on Chapter 9 of CompTIA Network+ Exam Guide, 4th ed., Mike Meyers Concepts application set transport set High-level, "Application Set" protocols deal only with how handled

### CSC 4900 Computer Networks: TCP

CSC 4900 Computer Networks: TCP Professor Henry Carter Fall 2017 Project 2: mymusic You will be building an application that allows you to synchronize your music across machines. The details of which are

### Chapter 2. Switch Concepts and Configuration. Part I

Chapter 2 Switch Concepts and Configuration Part I CCNA3-1 Chapter 2-1 Note for Instructors These presentations are the result of a collaboration among the instructors at St. Clair College in Windsor,

### ECE4110 Internetwork Programming. Introduction and Overview

ECE4110 Internetwork Programming Introduction and Overview 1 EXAMPLE GENERAL NETWORK ALGORITHM Listen to wire Are signals detected Detect a preamble Yes Read Destination Address No data carrying or noise?

### University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Sciences

University of California at Berkeley College of Engineering Department of Electrical Engineering and Computer Sciences CS168 MIDTERM EXAMINATION Monday, 20 October 2014 INSTRUCTIONS READ THEM NOW! This

### Important note! Please start with problems 1-4; because your grade is F if you do not reach at least 15 (fifteen) points out of 20 for problems 1-4!

Examination DD2392 Protocols and Principles of the Internet EP2120 Internetworking Date: 10 March 2009 at 8:00 13:00 a) No help material is allowed - You are not allowed to use dictionaries, books, or

### Network concepts introduction & wireshark

Network concepts introduction & wireshark W0RKSH0P @KirilsSolovjovs Why am I doing this? Many people attending hacker conferences are not in fact experts, but come here to learn and have fun Opportunity

### Computer Communication Networks Midterm Review

Computer Communication Networks Midterm Review ICEN/ICSI 416 Fall 2017 Prof. Dola Saha 1 Instructions Put your name and student id on each sheet of paper! The exam is closed book. You cannot use any computer