Transport Layer Protocols

Size: px
Start display at page:

Download "Transport Layer Protocols"

Transcription

1 Transport Layer Protocols Version. Transport layer performs two main tasks for the application layer by using the network layer. It provides end to end communication between two applications, and implements some control functions. The original TCP/IP protocol suite (to be introduced later) introduces two different protocols for this purpose: Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP establishes a virtual link between two application programs, and provides error checking and congestion control. On the other hand, UDP protocol keeps the minimum requirement of an end to end connection and leaves the control mechanisms to the application. TCP is a reliable and connection oriented protocol appropriate for applications such as delivery and file transfer protocol (FTP). The UDP is an unreliable and connectionless protocol, but it is simple and incurs less communication overhead. The UDP is a good choice for applications such as Voice over IP (VoIP), where packet loss is acceptable to some extent. In the following section, the TCP and UDP are introduced. Transmission Control Protocol (TCP) TCP is the main protocol of the transport layer in packet switched networks. TCP and IP protocols provide the basic structure of the Internet. These two protocols are complementary in the sense that IP facilitates packet forwarding irrespective of reliable packet delivery, whereas TCP is responsible for reliable packet delivery between applications. In the network layer, the order of packets during transmission may change, because, different packets may reach a destination on different routes. Moreover, some packets may be dropped due to the congestion and/or long delay in a node on the path. TCP protocol compensates for some of these deficiencies of the IP protocol, and controls the congestion in a network. 1

2 To implement reliable services, TCP deploys a numbering system as well as some control mechanisms. The numbering system determines byte, sequence, and acknowledgment numbers. The control mechanisms include flow, error, and congestion controls. The bytes of the data part of TCP segments are numbered by the protocol. In fact, the first byte of a data segment gets a sequence number explicitly, where as the following bytes get it implicitly. The number is put in the sequence number field of the segment header, and is used for flow and error control. In addition, the parties involved in a connection use the {byte number + 1} in their segment header as acknowledgment number. It indicates the byte number they expect to receive. For example, if the acknowledgement number of a segment header of one of the communication parties shows 34, that means the party has received all of the bytes from the beginning up to and including byte number 33, and now it is expecting to receive byte number 34. TCP connections are full duplex; each party has its own sequence and acknowledgment numbers for the transmitting stream. Flow control avoids data overflow at the receiver. In other words, the receiver tells the sender how much to send so that buffer overflow is avoided. Congestion control is implemented by the sender based on the level of congestion in a network. Error control mechanism provides a reliable service for TCP. The control mechanisms of TCP will be explained later on. Prior to that, TCP protocol suite is introduced to show the relevance between TCP and the upper and lower layer protocols. Also, the structure of a TCP segment and the concept of connection oriented TCP are described to help understanding the TCP control mechanisms. TCP/IP Protocol Suite TCP and IP protocols were introduced prior to the OSI (Open System Interconnection) model of the International Standards Organization. Therefore, the

3 protocol stack based on the TCP/IP, as shown in Fig.1, does not exactly match with the 7 layer OSI model. The TCP/IP protocol suite contains four layers of protocols (or five layers, depending on which reference you look at!) as defined below. Layer 4 Application Layer: This layer performs the functionalities of application, presentation and session layers of the OSI model. Application protocols such as SMTP (simple mail transfer protocol), FTP (file transfer protocol), and HTTP (hypertext transfer protocol) operate at this layer. Layer 3 Transport Layer: This layer performs the equivalent functions of the OSI transport layer as well as some OSI session layer functionalities. This layer provides different levels of reliable delivery service for the application layer depending on the application requirements. Layer Internet Layer: This layer handles routing tables and packet forwarding. Layer 1 Network Access Layer (Data Link + MAC + Physical): Connection to the physical environment and flow control are performed at this layer. The layer specifies the characteristics of the hardware and access methods. OSI TCP/IP Application Presentation Application Session Transport Transport Network Internet Data Link Network Interface Physical Fig. 1 OSI model versus TCP/IP model 3

4 TCP Segment In order to understand the TCP protocol, it is necessary to understand the various fields of a TCP segment header. These fields are described in this section. In the next sections, we describe how each field is utilized for each TCP service. The TCP Segment header is bytes long, but it may increase up to 6 bytes if an optional 4 byte is added to the header. The format of a segment is shown in Fig.. The meaning and purpose of each field is as follows: Source Port Address: A 16 bit address of the port number of the sender (application). Destination port address: A 16 bit address of the port number of the receiver (application). Sequence Number: A 3 bit address (sequence number) of first byte of data in each segment. In other words, the sequence number indicates the address of the first data byte in each segment for the receiver. Acknowledgment Number: A 3 bit byte number that the receiver expects to receive from the sender. An acknowledgment number, 13, means that all the bytes starting from the initial sequence number and up to and including byte number 1 have been successfully received. Header length: A 4 bit field that represents the header length in multiple of four bytes. Reserved: A 6 bit field reserved for the requirements of future protocol developments. 4

5 Control: A 6 bit field contains some flags for connection establishment, termination, abortion, flow control, and data transfer mode indication. Table 1 represents the usage of each flag. Source Port Destination Port Header Length Sequence Number Acknowledgment Number Reserved U A P R S F Window size Checksum Urgent Pointer Options Padding H e a d e r Data U: URG (Urgent) A: ACK P: PSH (Push) R: RST (Reset) S: SYN (Sync.) F: FIN (Finish) Fig. : TCP Segment Format Table 1 TCP Segment Header Flags Flag value Description URG 1 Urgent pointer field has a valid value. ACK 1 Acknowledgment field has a valid value. 1 PSH RST 1 SYN 1 FIN 1 The receiving TCP module passes (pushes) the data to the application immediately. The receiving TCP module may delay the data. The connection request is denied, or the connection is aborted. Synchronize sequence number during connection Sender has no more data to send, but is ready to receive. 5

6 Window Size: A 16 bit number specifying the number of bytes the receiver is willing to receive. The value of this field is used in flow control and congestion control. Checksum: A 16 bit field used for error correction. Urgent pointer: A 16 bit number that is added to the sequence number and shows the location of the first byte of urgent data in the data section of the segment. Urgent data is delivered to the recipient application program to be processed before other data. The value of this field is used when the URG flag is on. Options: The length of this field may reach up to 4 bytes. Connection oriented TCP TCP is a connection oriented protocol. It establishes a virtual connection between the running application programs (process) at the two communication end points. TCP uses port number for this purpose. Each port number is relevant to an application as shown in Table. The stream of data is sent from the process to the transport layer. TCP establishes a connection between the transport layers of the transmitter and receiver stations. It then divides the stream of data into units called segments. Segments are numbered and transmitted one by one. The TCP protocol at the receiver side checks the arriving segments for error, loss, and duplication. It orders the segments, makes a stream, and transfers the stream to the receiver side process. TCP provides stream delivery service. Both the sender and the receiver processes deal with the stream of bytes and are not aware of stream segmentation in the lower layers. After all segments are transmitted, TCP at the transmitter side closes the connection. 6

7 Table Port Numbers Used by TCP Port Protocol Description FTP, Data File Transfer Protocol (data connection) 1 FTP, Control File Transfer Protocol (control connection) 3 TELNET Terminal Network 5 SMTP Simple Mail Transfer Protocol 53 DNS Domain Name Server 79 Finger Finger 8 HTTP Hypertext Transfer Protocol 111 RPC Remote Procedure Call Connection oriented TCP consists of connection establishment, data transfer, and connection termination phases. The parties involved in a connection establishment are termed as client, applicant for the connection, and server, the destination. Connection establishment is a three way handshaking protocol. Fig. 3 shows a connection establishment. First, the client sends a segment with SYN=1 to synchronize the sequence numbers. The segment contains the initial sequence number. Second, the server sends the second segment with SYN and ACK flags on. That means the segment contains the initial sequence number of the server and the first segment transmitted by the client has been successfully received. The server s segment contains the value of the window size kept by the server. In the next sections we will describe the application of the window size. Third, the client sends the segment with ACK flag on which acknowledges the reception of the server segment reception. The window size of the client is included too. Note that the sequence number of the client s acknowledgment segment is the same as client s first segment (synchronizing segment), because no data is carried in the first segment and sequence number does not change. 7

8 Data transfer phase is bidirectional. It includes data and acknowledgement transmission. The acknowledgment is piggybacked with data or transmitted individually. Fig. 4 shows an example of data transfer. The client and the server have bytes of data (each one) to transmit. The client transmits the data in two segments, and the server transmits its data all at once. Acknowledgment is piggy backed with the three first segments. However, there is no more data to be transmitted at the last segment, and it carries only the acknowledgement. In the client s data segments, the PSH flag is on. It means the server TCP should deliver data to server application as soon as they are received (appropriate for interactive Client Server Seq# = 8, SYN=1 Seq#=15, Ack = 81, SYN=ACK=1, RWND = 5 Seq#=8, Ack = 151, ACK=1, RWND = 1 Time Time applications). Fig. 3 Three way connection establishment Client or server can terminate a connection, no matter which one has established it. Also, one party can terminate its connection, while it still receives data from the other party. The termination phase is implemented by terminating party which transmits a segment contains FIN flag on, with the last available chunk of data. The 8

9 recipient party acknowledges the connection termination by activating the ACK flag in its next segment. Client Server Seq# = 81, Ack=151, ACK=PSH=1 Data bytes: 81-9 Seq# = 91, Ack=151, ACK=PSH=1 Data bytes: 91-1 Seq#=151, Ack = 11, ACK=1 Data bytes: Seq#=1, Ack = 171, ACK=1, RWND = 1 Time Time Fig. 4 Data transfer Flow Control Flow control determines how much data can be transmitted before receiving an acknowledgment. There are two extremes for this purpose. One asks an acknowledgment after each one byte of data transmission, which causes delay and transmission overhead; the other asks for only one acknowledgment after transmission all of the data, which causes late feedback to the transmitter to compensate for transmission problems. For instance, if the path is congested, transmitter will not be aware of that to slow down the transmission rate. TCP flow control chooses a dynamic approach between these two extremes. 9

10 TCP flow control is window based. Window size specifies the amount of data that can be transmitted before receiving the acknowledgment. Window slides over the segments as shown in Fig 5. The size of the window varies according to the congestion status of a network, congestion window (CWND), and the receiver buffer size, receiver window (RWND). The congestion window size is determined by the network to avoid congestion. The receiver window indicates the number of bytes that the receiver can accept before its buffer overflows. The value of the receiver window is sent to the transmitter in the acknowledgment message. The size of the sliding window, shown in Fig. 5, is equal to the min (CWND, RWND). Accordingly, the sliding window resizes by opening from the right and closing from the left. Opening lets more bytes come to the window and closing lets the acknowledged bytes to go out of the window. Sliding window Sent Sent Waiting Not & ACKed bytes & not ACKed bytes to be sent in the window Byte stream Fig. 5 TCP sliding window Example: In the example, shown in Fig. 6, the CWND is and RWND is 9 bytes. Accordingly, TCP window size equals to 9. The bytes up to have been sent. Bytes number, 1, and has not been acknowledged by the receiver, but the sender can still transmit bytes 3 up to 8. 1

11 Next byte to be sent Sent and ACKed Can t be sent until window opens Window size=min(,9) Fig. 6 Sliding Window If the sender receives an acknowledgment value for byte 3 along with RWND = 9, the window will be updated. It is closed from the left and opened from the right. The new TCP window will contain bytes 3 up to 11. Question: window mechanism? What happens if the sender or transmitter is very slow in a sliding Answer: The Silly Window Syndrome occurs! The slow transaction of data causes the window size to be reduced down to one byte. Comparing the overhead of the segment, 4 bytes, with the body, one byte, shows flow control with sliding window mechanism is not efficient at all. Remedy: If the slowness of the sender s application causes Silly Window Syndrome, Nagle s Algorithm is the remedy. The prescription is as follows: Sender sends the first segment even if it is a small one Next, the sender waits until an ACK is received, or a maximum size segment is accumulated. 11

12 Step is repeated for the rest of the transmission. If the slowness of the receiver s application causes Silly Window Syndrome, two prescriptions are advised: Clark s solution: Send an ACK as soon as the data arrives, and close the window until another segment can be received or buffer is ½ empty. Delayed ACK: Delay sending the ACK, at most 5 ms; this causes the sender stop transmitting, but it does not change its window size. Error Control The reliability of TCP protocol is achieved by error control mechanisms that detect and correct errors. Error detection includes identifying corrupted, lost, out oforder, and duplicated segments. TCP deploys three tools for error detection and correction: checksum, acknowledgement, and time out. Checksum Checksum is a simple method for detecting corrupted segments. Each segment contains a 16 bit field in its header for checksum. Destination TCP discards segments that have checksum error. Acknowledgement Every data or control segment with sequence number is acknowledged to confirm the segment reception. There are two kinds of acknowledgement: positive acknowledgement (shortly ACK) and selective acknowledgement (SACK). Positive acknowledgement symbolizes the fact that the receiver advertises the expecting byte number and ignores reporting the erroneous segments. SACK is a 1

13 complementary mechanism for ACK that reports erroneous segments, such as duplicated and out of order segments, to the sender. Time out Retransmission This is a very important task of error control mechanism. Corrupted, lost, and delayed segments are retransmitted. The criteria for the retransmission are retransmission timer expiration or three duplicate ACK receptions. The TCP sender starts a retransmission time out (RTO) timer when it sends a segment. The segment is retransmitted upon RTO timer expiration, no matter what the reason is for not receiving ACK. For example if the segment is received successfully, but the ACK is lost or delayed, the TCP sender assumes segment has been lost. For this reason, the RTO timer is set for a longer time in networks with long round trip time (RTT). RTT is the time for a segment to catch the receiver plus the time for an ACK to reach to the segment transmitter. Network that needs fast retransmission, three duplicate ACK is the rule for retransmission. If the sender receives three ACKs for a sequence number, it sends the segment with that sequence number immediately, irrespective of the RTO timer value. The advantage of three duplicate ACK rule is the receiver does not need to buffer many segments until it finally receives an out of order segment. Congestion Control In a network, data are queued in the buffer of the interfaces and delivered to the next stage in an appropriate time. If there is a mismatch between processing time or capacity of the two interconnected stages of the network, congestion occurs. 13

14 Congestion affects two performance metrics in a network: throughput and delay. Delay can be considered as the sum of the propagation, processing, and queuing delay. Indeed, congestion affects queuing delay much more than the others. When the network load increases, congestion deteriorates the delay performance. This situation is depicted in Fig. 7. Again, increased delay worsens the congestion state. Because the sender attempts to retransmit a packet upon late ACK, which increases the network load further. Throughput and goodput are two performance measures that show the behaviour of the network versus load. Throughput is defined as the number of packets passing through the network in a unit of time. The measure of the received packets to the transmitted packets named goodput. As shown in Fig. 7, when the network load increases up to the network capacity, the throughput and goodput increase. However, when the traffic load is more than the network capacity, overflow occurs in the buffers and packets are dropped. Delay No congestion Network capacity congestion Total Output rate No congestion Network capacity congestion Network Load Total Input rate Fig. 7 Network performance upon congestion The principles of congestion control mechanisms are to prevent or remove congestion. Congestion prevention mechanisms control congestion by adopting a good retransmission, acknowledgement, and discard policy. Once congestion occurred, different signalling mechanisms are used by the routers to inform the sender or receiver of the congestion to compensate for that. Congestion can be avoided by appropriately adjusting the retransmission timers and choosing a retransmission policy. The time that a receiver sends an 14

15 acknowledgement affects the sender s transmission speed. So, by controlling this time, congestion can be controlled. For instance, if the receiver sends the acknowledgements later, but before the expiration of the sender s timer, the arrival traffic in a network slows down. Discard policy can prevent congestion by discarding the packets that have less effect on the transmission or application quality, e.g. discarding less important voice or video packets instead of an FTP session data packets. The above preventing mechanisms are open loop control mechanisms and can be implemented at sender or receiver side. To alleviate an occurred congestion, closed loop control mechanisms are used to slow down the arrival of traffic to a network. When a router experience congestion, it may ask the previous routers to slow down their packet transmissions. Inform directly senders or receivers, instead of routers on a path, to adjust the injected amount of data to the network could be another mechanism. In other words, congestion is controlled by TCP senders and receivers, not routers on a path. The main tool of closed loop congestion control mechanisms is window size. The window size is determined by the minimum value of available capacity of buffers in TCP receiver (RWND) or congestion level in the network (CWND). RWND is advertised from the receiver side and used for flow control. CWND size is determined on sender side and used for congestion control. TCP Congestion Policy TCP congestion control mechanism has three instruments: slow start, congestion avoidance, and congestion detection. A sender starts transmission with a slow rate and increases the rate as long as its rate is below a threshold. When the threshold is reached, the rate is decreased to avoid congestion. If congestion happens, the sender slows down the rate to the slow start rate or another rate of congestion avoidance phase depending on the chosen policy. 15

16 In slow start phase, a sender chooses the minimum value of CWND which has been agreed upon connection establishment. Suppose RWND is much higher than the CWND. After transmitting the first segment and receiving the corresponding ACK, sender doubles CWND. That means two segments can be transmitted before receiving an acknowledgement. If the sender receives ACK for the two transmitted segments, it doubles CWND again, as shown in Fig. 8. The process of increasing CWND exponentially stops and congestion avoidance phase starts when CWND size reaches a threshold value. CWND size increases in congestion avoidance phase linearly, not exponentially, as long as no congestion is detected. That means the sender increases CWND by one after receiving ACK, as shown in Fig. 9. The slow increment of CWND prevents congestion to some extent, but it can not 1% avoid that. Sender Receiver cwnd=1 Segment 1 cwnd = 1x = 1 = ACK Segment Segment 3 cwnd = x = = 4 ACK 4 Segment 4 Segment 5 Segment 6 Segment 7 cwnd = 4x = 3 = 8 ACK 8 Time Time Fig. 8 slow start phase A TCP sender assumes congestion happened upon RTO expiration or receiving three ACKs for a segment. A new slow start or congestion avoidance phase follows the congestion detection phase. If detection is based on time out, the threshold value will be set to the half of the current window size and CWND will be set by the minimum CWND size of the slow start phase. Otherwise, if detection is by three 16

17 ACKs, the threshold value will be set to the half of the current window size, CWND will be set by the threshold value, and a congestion avoidance phase starts. The different reaction to congestion detection is because of the fact that there is a stronger possibility of congestion when a time out occurs than three ACKs occur. In the former, there is no idea about the transmitted segments, but the later means some segments have reached the receiver successfully. Sender Receiver cwnd=1 Segment 1 cwnd = 1+1 = ACK Segment Segment 3 cwnd = +1 = 3 ACK 4 Segment 4 Segment 5 Segment 6 cwnd = 3+1 =4 ACK 7 Time Time Fig. 9 congestion avoidance phase In summary, the congestion control mechanism of TCP can be categorized in three phases. It starts with slow start phase that exponentially increase CWND and continues to congestion avoidance threshold. When it reaches the congestion avoidance threshold then it additively increases CWND, and follows by a multiplicative decreasing rate phase upon congestion detection. Fig. 1 illustrates the three phases. 17

18 cwnd Time-out 3-ACKs slow start additive increase slow start additive increase additive increase multiplicative decrease multiplicative decrease time Fig. 1 TCP congestion control behaviour User datagram protocol (UDP) UDP serves the application layer and network layer like TCP, but with more ease. Table 3 compares the two protocols from the viewpoint of services they provide to the transport layer. UDP uses port number for application to application communication, but it does not establish a connection as TCP does, so it is termed as connectionless. UDP sender transmits the data unit of the upper layer process and does not care if the transmission is reliable. In other words, if the data unit get lost due to the congestion or duplicated in the path, UDP does not recognize it. UDP does not deploy ACK, flow and congestion control. That s why UDP is unreliable. There is minimal error detection, and erroneous packets will be simply discarded. The beauty of UDP is its simplicity. The only overhead that UDP adds to the packet is to establish process to process communication, rather than a host to host communication of IP layer. Therefore, UDP is very suitable for small message communications or applications that do not need strong reliability, such as client/server request/reply or video conferencing. It can also be used in 18

19 applications that have internal error and flow control, such as Trivial File Transfer Protocol (TFTP). Table 3 TCP and UDP services comparison Service TCP UDP Using port number for process to process yes yes communication Establishing process to process connection yes no Increasing overhead & interaction b/w sender & yes no receiver Doing error control yes minimal Doing flow control yes no Sending ACK for received packet yes no The data unit of UDP consists of an 8 byte header and variable size data field as shown in Fig. 11. The header consists of the source and destination port number, total length, and checksum fields. Source Port Number 16 bits Total Length 16 bits Destination Port Number 16 bits Checksum 16 bits Data Fig. 11: User Datagram Format 19

20 UDP port numbers are same as the TCP port numbers. They allow different applications to maintain a specific path for their data. In other words, multiple applications can be distinguished with their port numbers. You can think of a port number as an associated number to an interface queue that the application in sender or receiver side keeps data in it before transmission or reception. Even if an application wants to communicate with multiple applications, it keeps one port number for all incoming and outgoing data. Port numbers can be reserved for an application. The total length field shows the UDP datagram size which is the sum of bytes contained in the header and data section (sometimes named payload). The maximum size of a datagram is bytes. The use of the checksum field is optional in UDP, unlike TCP. If the checksum is not calculated by the sender the field will be filled with zero.

Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation

Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation Improving the Performance of TCP Using Window Adjustment Procedure and Bandwidth Estimation R.Navaneethakrishnan Assistant Professor (SG) Bharathiyar College of Engineering and Technology, Karaikal, India.

More information

TCP over Multi-hop Wireless Networks * Overview of Transmission Control Protocol / Internet Protocol (TCP/IP) Internet Protocol (IP)

TCP over Multi-hop Wireless Networks * Overview of Transmission Control Protocol / Internet Protocol (TCP/IP) Internet Protocol (IP) TCP over Multi-hop Wireless Networks * Overview of Transmission Control Protocol / Internet Protocol (TCP/IP) *Slides adapted from a talk given by Nitin Vaidya. Wireless Computing and Network Systems Page

More information

This sequence diagram was generated with EventStudio System Designer (http://www.eventhelix.com/eventstudio).

This sequence diagram was generated with EventStudio System Designer (http://www.eventhelix.com/eventstudio). Client App Network Server App 25-May-13 15:32 (Page 1) This sequence diagram was generated with EventStudio System Designer (http://www.eventhelix.com/eventstudio). TCP is an end to end protocol which

More information

Access Control: Firewalls (1)

Access Control: Firewalls (1) Access Control: Firewalls (1) World is divided in good and bad guys ---> access control (security checks) at a single point of entry/exit: in medieval castles: drawbridge in corporate buildings: security/reception

More information

First Midterm for ECE374 03/24/11 Solution!!

First Midterm for ECE374 03/24/11 Solution!! 1 First Midterm for ECE374 03/24/11 Solution!! Note: In all written assignments, please show as much of your work as you can. Even if you get a wrong answer, you can get partial credit if you show your

More information

Module 7 Internet And Internet Protocol Suite

Module 7 Internet And Internet Protocol Suite Module 7 Internet And Internet Protocol Suite Lesson 21 Internet and IPv4 LESSON OBJECTIVE General The lesson will discuss a popular network layer protocol, i.e. the Internet Protocol Specific The focus

More information

EINDHOVEN UNIVERSITY OF TECHNOLOGY Department of Mathematics and Computer Science

EINDHOVEN UNIVERSITY OF TECHNOLOGY Department of Mathematics and Computer Science EINDHOVEN UNIVERSITY OF TECHNOLOGY Department of Mathematics and Computer Science Examination Computer Networks (2IC15) on Monday, June 22 nd 2009, 9.00h-12.00h. First read the entire examination. There

More information

Encapsulating Voice in IP Packets

Encapsulating Voice in IP Packets Encapsulating Voice in IP Packets Major VoIP Protocols This topic defines the major VoIP protocols and matches them with the seven layers of the OSI model. Major VoIP Protocols 15 The major VoIP protocols

More information

Multiple Choice Questions

Multiple Choice Questions Comp18112: VoIP Examples/Revision 1 Barry 7/03/11 University of Manchester School of Computer Science COMP18112: Foundations of Distributed Computing 2011 Voice over Internet Protocol (VoIP) Questions

More information

Servicesin ns-3. Outline SIMULACIÓN DE PROTOCOLOS DE ENRUTAMIENTO PARA REDES MÓVILES AD-HOC MEDIANTE HERRRAMIENTA DE SIMULACIÓN NS-3

Servicesin ns-3. Outline SIMULACIÓN DE PROTOCOLOS DE ENRUTAMIENTO PARA REDES MÓVILES AD-HOC MEDIANTE HERRRAMIENTA DE SIMULACIÓN NS-3 SIMULACIÓN DE PROTOCOLOS DE ENRUTAMIENTO PARA REDES MÓVILES AD-HOC MEDIANTE HERRRAMIENTA DE SIMULACIÓN NS-3 Servicesin Outline 1. Services in Sockets UDP TCP Bulk Application FTP On off Application 2.

More information

DATA COMMUNICATION AND NETWORKS

DATA COMMUNICATION AND NETWORKS DATA COMMUNICATION AND NETWORKS 1. Define the term Computer Networks. A Computer network is a number if computers interconnected by one or more transmission paths. The transmission path often is the telephone

More information

Layer 7 Load Balancing and Content Customization

Layer 7 Load Balancing and Content Customization C H A P T E R 4 Layer 7 Load Balancing and Content Customization This chapter will discuss the methods and protocols involved in accomplishing a Layer 7 load-balancing solution. The reasons for and benefits

More information

Introduction to VoIP. 陳 懷 恩 博 士 助 理 教 授 兼 計 算 機 中 心 資 訊 網 路 組 組 長 國 立 宜 蘭 大 學 資 工 系 Email: wechen@niu.edu.tw TEL: 03-9357400 # 340

Introduction to VoIP. 陳 懷 恩 博 士 助 理 教 授 兼 計 算 機 中 心 資 訊 網 路 組 組 長 國 立 宜 蘭 大 學 資 工 系 Email: wechen@niu.edu.tw TEL: 03-9357400 # 340 Introduction to VoIP 陳 懷 恩 博 士 助 理 教 授 兼 計 算 機 中 心 資 訊 網 路 組 組 長 國 立 宜 蘭 大 學 資 工 系 Email: wechen@niu.edu.tw TEL: 3-93574 # 34 Outline Introduction VoIP Call Tpyes VoIP Equipments Speech and Codecs Transport

More information

Ina Minei Reuven Cohen. The Technion. Haifa 32000, Israel. e-mail: faminei,rcoheng@cs.technion.ac.il. Abstract

Ina Minei Reuven Cohen. The Technion. Haifa 32000, Israel. e-mail: faminei,rcoheng@cs.technion.ac.il. Abstract High Speed Internet Access Through Unidirectional Geostationary Satellite Channels Ina Minei Reuven Cohen Computer Science Department The Technion Haifa 32000, Israel e-mail: faminei,rcoheng@cs.technion.ac.il

More information

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc (International Journal of Computer Science & Management Studies) Vol. 17, Issue 01 Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc Dr. Khalid Hamid Bilal Khartoum, Sudan dr.khalidbilal@hotmail.com

More information

Voice over IP: RTP/RTCP The transport layer

Voice over IP: RTP/RTCP The transport layer Advanced Networking Voice over IP: /RTCP The transport layer Renato Lo Cigno Requirements For Real-Time Transmission Need to emulate conventional telephone system Isochronous output timing same with input

More information

FEW would argue that one of TCP s strengths lies in its

FEW would argue that one of TCP s strengths lies in its IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 13, NO. 8, OCTOBER 1995 1465 TCP Vegas: End to End Congestion Avoidance on a Global Internet Lawrence S. Brakmo, Student Member, IEEE, and Larry L.

More information

CYBER ATTACKS EXPLAINED: PACKET CRAFTING

CYBER ATTACKS EXPLAINED: PACKET CRAFTING CYBER ATTACKS EXPLAINED: PACKET CRAFTING Protect your FOSS-based IT infrastructure from packet crafting by learning more about it. In the previous articles in this series, we explored common infrastructure

More information

Attack Lab: Attacks on TCP/IP Protocols

Attack Lab: Attacks on TCP/IP Protocols Laboratory for Computer Security Education 1 Attack Lab: Attacks on TCP/IP Protocols Copyright c 2006-2010 Wenliang Du, Syracuse University. The development of this document is funded by the National Science

More information

Quality of Service (QoS) on Netgear switches

Quality of Service (QoS) on Netgear switches Quality of Service (QoS) on Netgear switches Section 1 Principles and Practice of QoS on IP networks Introduction to QoS Why? In a typical modern IT environment, a wide variety of devices are connected

More information

Clearing the Way for VoIP

Clearing the Way for VoIP Gen2 Ventures White Paper Clearing the Way for VoIP An Alternative to Expensive WAN Upgrades Executive Overview Enterprises have traditionally maintained separate networks for their voice and data traffic.

More information

Computer Networks and the Internet

Computer Networks and the Internet ? Computer the IMT2431 - Data Communication and Network Security January 7, 2008 ? Teachers are Lasse Øverlier and http://www.hig.no/~erikh Lectures and Lab in A126/A115 Course webpage http://www.hig.no/imt/in/emnesider/imt2431

More information

Load Balancing. Final Network Exam LSNAT. Sommaire. How works a "traditional" NAT? Un article de Le wiki des TPs RSM.

Load Balancing. Final Network Exam LSNAT. Sommaire. How works a traditional NAT? Un article de Le wiki des TPs RSM. Load Balancing Un article de Le wiki des TPs RSM. PC Final Network Exam Sommaire 1 LSNAT 1.1 Deployement of LSNAT in a globally unique address space (LS-NAT) 1.2 Operation of LSNAT in conjunction with

More information

Linux 2.4 Implementation of Westwood+ TCP with rate-halving: A Performance Evaluation over the Internet

Linux 2.4 Implementation of Westwood+ TCP with rate-halving: A Performance Evaluation over the Internet Linux. Implementation of TCP with rate-halving: A Performance Evaluation over the Internet A. Dell Aera, L. A. Grieco, S. Mascolo Dipartimento di Elettrotecnica ed Elettronica Politecnico di Bari Via Orabona,

More information

3. MONITORING AND TESTING THE ETHERNET NETWORK

3. MONITORING AND TESTING THE ETHERNET NETWORK 3. MONITORING AND TESTING THE ETHERNET NETWORK 3.1 Introduction The following parameters are covered by the Ethernet performance metrics: Latency (delay) the amount of time required for a frame to travel

More information

Network traffic monitoring and management. Sonia Panchen sonia.panchen@inmon.com 11 th November 2010

Network traffic monitoring and management. Sonia Panchen sonia.panchen@inmon.com 11 th November 2010 Network traffic monitoring and management Sonia Panchen sonia.panchen@inmon.com 11 th November 2010 Lecture outline What is network traffic management? Traffic management applications Traffic monitoring

More information

Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Ernie Gilman

Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Ernie Gilman Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Ernie Gilman IBM Sr Consulting IT Specialist Session 10723 Agenda Overview of OMEGAMON for Mainframe Networks FP3 and z/os 1.12 1.OSA Express

More information

CSE331: Introduction to Networks and Security. Lecture 12 Fall 2006

CSE331: Introduction to Networks and Security. Lecture 12 Fall 2006 CSE331: Introduction to Networks and Security Lecture 12 Fall 2006 Announcements Midterm I will be held Friday, Oct. 6th. True/False Multiple Choice Calculation Short answer Short essay Project 2 is on

More information

Understanding IP Faxing (Fax over IP)

Understanding IP Faxing (Fax over IP) Understanding IP Faxing (Fax over IP) A detailed technical overview of how VoIP technology and IP Faxing (Fax over IP) are changing the way organizations utilize existing network infrastructures for voice

More information

Firewalls. Firewalls. Idea: separate local network from the Internet 2/24/15. Intranet DMZ. Trusted hosts and networks. Firewall.

Firewalls. Firewalls. Idea: separate local network from the Internet 2/24/15. Intranet DMZ. Trusted hosts and networks. Firewall. Firewalls 1 Firewalls Idea: separate local network from the Internet Trusted hosts and networks Firewall Intranet Router DMZ Demilitarized Zone: publicly accessible servers and networks 2 1 Castle and

More information

A Network-Controlled Architecture for SCTP Hard Handover

A Network-Controlled Architecture for SCTP Hard Handover A Network-Controlled Architecture for SCTP Hard Handover Khadija Daoud, Karine Guillouard, Philippe Herbelin Orange Labs, Issy Les Moulineaux, France {first name.last name}@orange-ftgroup.com Abstract

More information

Linux MDS Firewall Supplement

Linux MDS Firewall Supplement Linux MDS Firewall Supplement Table of Contents Introduction... 1 Two Options for Building a Firewall... 2 Overview of the iptables Command-Line Utility... 2 Overview of the set_fwlevel Command... 2 File

More information

Summer Workshop on Cyber Security

Summer Workshop on Cyber Security Summer Workshop on Cyber Security Computer s Security (Part 1) Dr. Hamed Mohsenian-Rad University of California at Riverside and Texas Tech University August 12-16, 2013 Supported by National Science Foundation

More information

ECSE-6600: Internet Protocols Exam 2

ECSE-6600: Internet Protocols Exam 2 ECSE-6600: Internet Protocols Exam 2 Time: 75 min (strictly enforced) Points: 50 YOUR NAME: Be brief, but DO NOT omit necessary detail {Note: Simply copying text directly from the slides or notes will

More information

VoIP in 3G Networks: An End-to- End Quality of Service Analysis

VoIP in 3G Networks: An End-to- End Quality of Service Analysis VoIP in 3G etworks: An End-to- End Quality of Service Analysis 1 okia etworks P.O.Box 301, 00045 okia Group, Finland renaud.cuny@nokia.com Renaud Cuny 1, Ari Lakaniemi 2 2 okia Research Center P.O.Box

More information

Linux TCP Implementation Issues in High-Speed Networks

Linux TCP Implementation Issues in High-Speed Networks Linux TCP Implementation Issues in High-Speed Networks D.J.Leith Hamilton Institute, Ireland www.hamilton.ie 1. Implementation Issues 1.1. SACK algorithm inefficient Packets in flight and not yet acknowledged

More information

Ignoring the Great Firewall of China

Ignoring the Great Firewall of China An Overview of Ignoring the Great Firewall of China By: Matt Landau Original Paper: Ignoring the Great Firewall of China Richard Clayton, Steven J. Murdoch, and Robert N. M. Watson University of Cambridge,

More information

IOS Server Load Balancing

IOS Server Load Balancing IOS Server Load Balancing This feature module describes the Cisco IOS Server Load Balancing (SLB) feature. It includes the following sections: Feature Overview, page 1 Supported Platforms, page 5 Supported

More information

Security (II) ISO 7498-2: Security Architecture of OSI Reference Model. Outline. Course Outline: Fundamental Topics. EE5723/EE4723 Spring 2012

Security (II) ISO 7498-2: Security Architecture of OSI Reference Model. Outline. Course Outline: Fundamental Topics. EE5723/EE4723 Spring 2012 Course Outline: Fundamental Topics System View of Network Security Network Security Model Security Threat Model & Security Services Model Overview of Network Security Security Basis: Cryptography Secret

More information

CS 457 Lecture 19 Global Internet - BGP. Fall 2011

CS 457 Lecture 19 Global Internet - BGP. Fall 2011 CS 457 Lecture 19 Global Internet - BGP Fall 2011 Decision Process Calculate degree of preference for each route in Adj-RIB-In as follows (apply following steps until one route is left): select route with

More information

The Internet. Chapter 10. Learning Objectives. Chapter Outline. After reading this chapter, you should be able to:

The Internet. Chapter 10. Learning Objectives. Chapter Outline. After reading this chapter, you should be able to: The Internet Chapter 10 Learning Objectives After reading this chapter, you should be able to: Discuss the responsibilities of the Internet Protocol (IP) and how IP can be used to create a connection between

More information

Improving Effective WAN Throughput for Large Data Flows By Peter Sevcik and Rebecca Wetzel November 2008

Improving Effective WAN Throughput for Large Data Flows By Peter Sevcik and Rebecca Wetzel November 2008 Improving Effective WAN Throughput for Large Data Flows By Peter Sevcik and Rebecca Wetzel November 2008 When you buy a broadband Wide Area Network (WAN) you want to put the entire bandwidth capacity to

More information

Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme

Lehrstuhl für Informatik 4 Kommunikation und verteilte Systeme Chapter 2: Representation of Multimedia Data Chapter 3: Multimedia Systems Communication Aspects and Services Multimedia Applications and Communication Protocols Quality of Service and Resource Management

More information

All Rights Reserved - Library of University of Jordan - Center of Thesis Deposit

All Rights Reserved - Library of University of Jordan - Center of Thesis Deposit iii DEDICATION To my parents, my wife, my brothers and sisters, and my son for their encouragement, and help during this thesis. iv ACKNOWLEDGEMENT I would like to thank my supervisor prof. Jameel Ayoub

More information

Network Layer. Introduction Datagrams and Virtual Circuits Routing Traffic Control. Data delivery from source to destination.

Network Layer. Introduction Datagrams and Virtual Circuits Routing Traffic Control. Data delivery from source to destination. Layer Introduction Datagrams and Virtual ircuits Routing Traffic ontrol Main Objective Data delivery from source to destination Node (Router) Application Presentation Session Transport Data Link Data Link

More information

AFDX networks. Computers and Real-Time Group, University of Cantabria

AFDX networks. Computers and Real-Time Group, University of Cantabria AFDX networks By: J. Javier Gutiérrez (gutierjj@unican.es) Computers and Real-Time Group, University of Cantabria ArtistDesign Workshop on Real-Time System Models for Schedulability Analysis Santander,

More information

MONITORING OF TRAFFIC OVER THE VICTIM UNDER TCP SYN FLOOD IN A LAN

MONITORING OF TRAFFIC OVER THE VICTIM UNDER TCP SYN FLOOD IN A LAN MONITORING OF TRAFFIC OVER THE VICTIM UNDER TCP SYN FLOOD IN A LAN Kanika 1, Renuka Goyal 2, Gurmeet Kaur 3 1 M.Tech Scholar, Computer Science and Technology, Central University of Punjab, Punjab, India

More information

VoIP QoS. Version 1.0. September 4, 2006. AdvancedVoIP.com. sales@advancedvoip.com support@advancedvoip.com. Phone: +1 213 341 1431

VoIP QoS. Version 1.0. September 4, 2006. AdvancedVoIP.com. sales@advancedvoip.com support@advancedvoip.com. Phone: +1 213 341 1431 VoIP QoS Version 1.0 September 4, 2006 AdvancedVoIP.com sales@advancedvoip.com support@advancedvoip.com Phone: +1 213 341 1431 Copyright AdvancedVoIP.com, 1999-2006. All Rights Reserved. No part of this

More information

Modeling and Simulation of Queuing Scheduling Disciplines on Packet Delivery for Next Generation Internet Streaming Applications

Modeling and Simulation of Queuing Scheduling Disciplines on Packet Delivery for Next Generation Internet Streaming Applications Modeling and Simulation of Queuing Scheduling Disciplines on Packet Delivery for Next Generation Internet Streaming Applications Sarhan M. Musa Mahamadou Tembely Matthew N. O. Sadiku Pamela H. Obiomon

More information

Chapter 16: Distributed Operating Systems

Chapter 16: Distributed Operating Systems Module 16: Distributed ib System Structure, Silberschatz, Galvin and Gagne 2009 Chapter 16: Distributed Operating Systems Motivation Types of Network-Based Operating Systems Network Structure Network Topology

More information

Module 15: Network Structures

Module 15: Network Structures Module 15: Network Structures Background Topology Network Types Communication Communication Protocol Robustness Design Strategies 15.1 A Distributed System 15.2 Motivation Resource sharing sharing and

More information

6.6 Scheduling and Policing Mechanisms

6.6 Scheduling and Policing Mechanisms 02-068 C06 pp4 6/14/02 3:11 PM Page 572 572 CHAPTER 6 Multimedia Networking 6.6 Scheduling and Policing Mechanisms In the previous section, we identified the important underlying principles in providing

More information

VXLAN: Scaling Data Center Capacity. White Paper

VXLAN: Scaling Data Center Capacity. White Paper VXLAN: Scaling Data Center Capacity White Paper Virtual Extensible LAN (VXLAN) Overview This document provides an overview of how VXLAN works. It also provides criteria to help determine when and where

More information

Chapter 2 Voice over Internet Protocol

Chapter 2 Voice over Internet Protocol Chapter 2 Voice over Internet Protocol Abstract This chapter presents an overview of the architecture and protocols involved in implementing VoIP networks. After the overview, the chapter discusses the

More information

Latency on a Switched Ethernet Network

Latency on a Switched Ethernet Network Application Note 8 Latency on a Switched Ethernet Network Introduction: This document serves to explain the sources of latency on a switched Ethernet network and describe how to calculate cumulative latency

More information

IAB CONCERNS ABOUT CONGESTION CONTROL. Iffat Hasnian 1832659

IAB CONCERNS ABOUT CONGESTION CONTROL. Iffat Hasnian 1832659 IAB CONCERNS ABOUT CONGESTION CONTROL Iffat Hasnian 1832659 IAB CONCERNS Outline 1- Introduction 2- Persistent High Drop rate Problem 3- Current Efforts in the IETF 3.1 RTP 3.2 TFRC 3.3 DCCP 3.4 Audio

More information

D1.2 Network Load Balancing

D1.2 Network Load Balancing D1. Network Load Balancing Ronald van der Pol, Freek Dijkstra, Igor Idziejczak, and Mark Meijerink SARA Computing and Networking Services, Science Park 11, 9 XG Amsterdam, The Netherlands June ronald.vanderpol@sara.nl,freek.dijkstra@sara.nl,

More information

Security Technology White Paper

Security Technology White Paper Security Technology White Paper Issue 01 Date 2012-10-30 HUAWEI TECHNOLOGIES CO., LTD. 2012. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means without

More information

Accelerating File Transfers Increase File Transfer Speeds in Poorly-Performing Networks

Accelerating File Transfers Increase File Transfer Speeds in Poorly-Performing Networks Accelerating File Transfers Increase File Transfer Speeds in Poorly-Performing Networks Contents Introduction... 2 Common File Delivery Methods... 2 Understanding FTP... 3 Latency and its effect on FTP...

More information

Secure Network Access System (SNAS) Indigenous Next Generation Network Security Solutions

Secure Network Access System (SNAS) Indigenous Next Generation Network Security Solutions Secure Network Access System (SNAS) Indigenous Next Generation Network Security Solutions Gigi Joseph, Computer Division,BARC. Gigi@barc.gov.in Intranet Security Components Network Admission Control (NAC)

More information

Indepth Voice over IP and SIP Networking Course

Indepth Voice over IP and SIP Networking Course Introduction SIP is fast becoming the Voice over IP protocol of choice. During this 3-day course delegates will examine SIP technology and architecture and learn how a functioning VoIP service can be established.

More information

CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle

CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle SYBEX Preview Chapter CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle Chapter 2: Internet Protocols Copyright 2004 SYBEX Inc., 1151 Marina Village Parkway, Alameda,

More information

Test Methodology White Paper. Author: SamKnows Limited

Test Methodology White Paper. Author: SamKnows Limited Test Methodology White Paper Author: SamKnows Limited Contents 1 INTRODUCTION 3 2 THE ARCHITECTURE 4 2.1 Whiteboxes 4 2.2 Firmware Integration 4 2.3 Deployment 4 2.4 Operation 5 2.5 Communications 5 2.6

More information

Technote. SmartNode Quality of Service for VoIP on the Internet Access Link

Technote. SmartNode Quality of Service for VoIP on the Internet Access Link Technote SmartNode Quality of Service for VoIP on the Internet Access Link Applies to the following products SmartNode 1000 Series SmartNode 2000 Series SmartNode 4520 Series Overview Initially designed

More information

Performance monitoring and analysis of wireless communication protocols for mobile devices

Performance monitoring and analysis of wireless communication protocols for mobile devices Performance monitoring and analysis of wireless communication protocols for mobile devices Almudena Díaz, Pedro Merino, F. Javier Rivas Departamento de Lenguajes y Ciencias de la Computación, University

More information

On the Efficiency and Fairness of TCP over Wired/Wireless Networks. Dimitrios Vardalis. Master of Science in Computer Science

On the Efficiency and Fairness of TCP over Wired/Wireless Networks. Dimitrios Vardalis. Master of Science in Computer Science On the Efficiency and Fairness of TCP over Wired/Wireless Networks by Dimitrios Vardalis Master of Science in Computer Science State University of New York at Stony Brook 2001 The continuous growth in

More information

A Network Monitoring System with a Peer-to-Peer Architecture

A Network Monitoring System with a Peer-to-Peer Architecture A Network Monitoring System with a Peer-to-Peer Architecture Paulo Salvador, Rui Valadas University of Aveiro / Institute of Telecommunications Aveiro E-mail: salvador@av.it.pt; rv@det.ua.pt Abstract The

More information

Algemene Theorie en Vaardigheden 2. April 2014 Theaterschool OTT-2 1

Algemene Theorie en Vaardigheden 2. April 2014 Theaterschool OTT-2 1 Les 6 Showcontrol April 2014 Theaterschool OTT-2 1 OSI layers versus equipment Layer 1: Physical Network Interface Card (NIC) Hub (multiport repeater) Modem (modulator/demodulator, converts signals) Layer

More information

Stateful Firewalls. Hank and Foo

Stateful Firewalls. Hank and Foo Stateful Firewalls Hank and Foo 1 Types of firewalls Packet filter (stateless) Proxy firewalls Stateful inspection Deep packet inspection 2 Packet filter (Access Control Lists) Treats each packet in isolation

More information

TRANSPORT LAYER AND SECURITY PROTOCOLS FOR AD HOC WIRELESS NETWORKS

TRANSPORT LAYER AND SECURITY PROTOCOLS FOR AD HOC WIRELESS NETWORKS Chapter 9 TRANSPORT LAYER AND SECURITY PROTOCOLS FOR AD HOC WIRELESS NETWORKS 9.1 INTRODUCTION The objectives of a transport layer protocol include the setting up of an end-to-end connection, end-to-end

More information

Chapter 12 Supporting Network Address Translation (NAT)

Chapter 12 Supporting Network Address Translation (NAT) [Previous] [Next] Chapter 12 Supporting Network Address Translation (NAT) About This Chapter Network address translation (NAT) is a protocol that allows a network with private addresses to access information

More information

CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle

CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle SYBEX Preview Chapter CCNA : Cisco Certified Network Associate Study Guide, 5th Edition (640-801) Todd Lammle Chapter 1: Internetworking Copyright 2004 SYBEX Inc., 1151 Marina Village Parkway, Alameda,

More information

Zarządzanie sieciami telekomunikacyjnymi

Zarządzanie sieciami telekomunikacyjnymi What Is an Internetwork? An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. Internetworking refers to the industry,

More information

Safeguards Against Denial of Service Attacks for IP Phones

Safeguards Against Denial of Service Attacks for IP Phones W H I T E P A P E R Denial of Service (DoS) attacks on computers and infrastructure communications systems have been reported for a number of years, but the accelerated deployment of Voice over IP (VoIP)

More information

MANAGING NETWORK COMPONENTS USING SNMP

MANAGING NETWORK COMPONENTS USING SNMP MANAGING NETWORK COMPONENTS USING SNMP Abubucker Samsudeen Shaffi 1 Mohanned Al-Obaidy 2 Gulf College 1, 2 Sultanate of Oman. Email: abobacker.shaffi@gulfcollegeoman.com mohaned@gulfcollegeoman.com Abstract:

More information

Application Note Telephony Service over Satellite

Application Note Telephony Service over Satellite Voice over Application Note Telephony Service over Satellite January 2012 Data Sells but Voice Pays In the early years of the industry, networks were deployed primarily for telephony services. As time

More information

OpenFlow Based Load Balancing

OpenFlow Based Load Balancing OpenFlow Based Load Balancing Hardeep Uppal and Dane Brandon University of Washington CSE561: Networking Project Report Abstract: In today s high-traffic internet, it is often desirable to have multiple

More information

Project Code: SPBX. Project Advisor : Aftab Alam. Project Team: Umair Ashraf 03-1853 (Team Lead) Imran Bashir 02-1658 Khadija Akram 04-0080

Project Code: SPBX. Project Advisor : Aftab Alam. Project Team: Umair Ashraf 03-1853 (Team Lead) Imran Bashir 02-1658 Khadija Akram 04-0080 Test Cases Document VOIP SOFT PBX Project Code: SPBX Project Advisor : Aftab Alam Project Team: Umair Ashraf 03-1853 (Team Lead) Imran Bashir 02-1658 Khadija Akram 04-0080 Submission Date:23-11-2007 SPBX

More information

VoIP telephony over internet

VoIP telephony over internet VoIP telephony over internet Yatindra Nath Singh, Professor, Electrical Engineering Department, Indian Institute of Technology Kanpur, Uttar Pradesh India. http://home.iitk.ac.in/~ynsingh MOOC on M4D (c)

More information

CS 356 Lecture 27 Internet Security Protocols. Spring 2013

CS 356 Lecture 27 Internet Security Protocols. Spring 2013 CS 356 Lecture 27 Internet Security Protocols Spring 2013 Review Chapter 1: Basic Concepts and Terminology Chapter 2: Basic Cryptographic Tools Chapter 3 User Authentication Chapter 4 Access Control Lists

More information

Research on Errors of Utilized Bandwidth Measured by NetFlow

Research on Errors of Utilized Bandwidth Measured by NetFlow Research on s of Utilized Bandwidth Measured by NetFlow Haiting Zhu 1, Xiaoguo Zhang 1,2, Wei Ding 1 1 School of Computer Science and Engineering, Southeast University, Nanjing 211189, China 2 Electronic

More information

ECE 578 Term Paper Network Security through IP packet Filtering

ECE 578 Term Paper Network Security through IP packet Filtering ECE 578 Term Paper Network Security through IP packet Filtering Cheedu Venugopal Reddy Dept of Electrical Eng and Comp science Oregon State University Bin Cao Dept of electrical Eng and Comp science Oregon

More information

Load Balance Router R258V

Load Balance Router R258V Load Balance Router R258V Specification Hardware Interface WAN - 5 * 10/100M bps Ethernet LAN - 8 * 10/100M bps Switch Reset Switch LED Indicator Power - Push to load factory default value or back to latest

More information

The Network Layer Functions: Congestion Control

The Network Layer Functions: Congestion Control The Network Layer Functions: Congestion Control Network Congestion: Characterized by presence of a large number of packets (load) being routed in all or portions of the subnet that exceeds its link and

More information

Load Balancing and Sessions. C. Kopparapu, Load Balancing Servers, Firewalls and Caches. Wiley, 2002.

Load Balancing and Sessions. C. Kopparapu, Load Balancing Servers, Firewalls and Caches. Wiley, 2002. Load Balancing and Sessions C. Kopparapu, Load Balancing Servers, Firewalls and Caches. Wiley, 2002. Scalability multiple servers Availability server fails Manageability Goals do not route to it take servers

More information

The Conversion Technology Experts. Quality of Service (QoS) in High-Priority Applications

The Conversion Technology Experts. Quality of Service (QoS) in High-Priority Applications The Conversion Technology Experts Quality of Service (QoS) in High-Priority Applications Abstract It is apparent that with the introduction of new technologies such as Voice over IP and digital video,

More information

Application Level Network Performance Monitoring

Application Level Network Performance Monitoring Application Level Network Performance Monitoring Manuel Stich Master's Thesis August 26, 2011 School of Computer and Communication Sciences Ecole Polytechnique Fédérale de Lausanne Supervisor: Prof. Patrick

More information

Defending against a Denial-of-Service Attack on TCP

Defending against a Denial-of-Service Attack on TCP Defending against a Denial-of-Service Attack on TCP Pars Mutaf pars@likya.iyte.edu.tr Department of Computer Engineering Izmir Institute of Technology Gaziosmanpasa Blv. No. 16 Cankaya Izmir 323 Turkey

More information

Elfiq Link Load Balancer Frequently Asked Questions (FAQ)

Elfiq Link Load Balancer Frequently Asked Questions (FAQ) lin Elfiq Link Load Balancer Frequently Asked Questions (FAQ) For Elfiq Operating System (EOS) version 3.1.x Document Revision 1.8 May 2006 Elfiq Solutions www.elfiq.com Page 2 / 14 Table of contents 1

More information

Combining Voice over IP with Policy-Based Quality of Service

Combining Voice over IP with Policy-Based Quality of Service TechBrief Extreme Networks Introduction Combining Voice over IP with Policy-Based Quality of Service Businesses have traditionally maintained separate voice and data networks. A key reason for this is

More information

Comparison of Voice over IP with circuit switching techniques

Comparison of Voice over IP with circuit switching techniques Comparison of Voice over IP with circuit switching techniques Author Richard Sinden Richard Sinden 1 of 9 Abstract Voice-over-IP is a growing technology. Companies are beginning to consider commercial

More information

Always Best Packet Switching: the mobile VoIP case study

Always Best Packet Switching: the mobile VoIP case study Always Best Packet Switching: the mobile VoIP case study Vittorio Ghini, Giorgia Lodi and Fabio Panzieri Dept. of Computer Science, University of Bologna, Italy Email: {ghini, lodig, panzieri}@cs.unibo.it

More information

ENSC 427: COMMUNICATION NETWORKS ANALYSIS ON VOIP USING OPNET

ENSC 427: COMMUNICATION NETWORKS ANALYSIS ON VOIP USING OPNET ENSC 427: COMMUNICATION NETWORKS ANALYSIS ON VOIP USING OPNET FINAL PROJECT Benson Lam 301005441 btl2@sfu.ca Winfield Zhao 200138485 wzhao@sfu.ca Mincong Luo 301039612 mla22@sfu.ca Data: April 05, 2009

More information

Network Security Part II: Standards

Network Security Part II: Standards Network Security Part II: Standards Raj Jain Washington University Saint Louis, MO 63131 Jain@cse.wustl.edu These slides are available on-line at: http://www.cse.wustl.edu/~jain/cse473-05/ 18-1 Overview

More information

Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Session 11899

Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Session 11899 Top 10 Tips for z/os Network Performance Monitoring with OMEGAMON Session 11899 Dean Butler butlerde@us.ibm.com 2012 IBM Corporation Agenda IBM Software Group Tivoli software Best Practices in Monitoring

More information

Serial Communications

Serial Communications Serial Communications 1 Serial Communication Introduction Serial communication buses Asynchronous and synchronous communication UART block diagram UART clock requirements Programming the UARTs Operation

More information

Agenda. Distributed System Structures. Why Distributed Systems? Motivation

Agenda. Distributed System Structures. Why Distributed Systems? Motivation Agenda Distributed System Structures CSCI 444/544 Operating Systems Fall 2008 Motivation Network structure Fundamental network services Sockets and ports Client/server model Remote Procedure Call (RPC)

More information

Multiple WiFi Clients on a Single Wireless Card

Multiple WiFi Clients on a Single Wireless Card Multiple WiFi Clients on a Single Wireless Card Juan M Torrescusa Supervisor: Andrea Bittau April 27, 2006 This report is submitted as part requirement for the BSc Degree in Computer Science at University

More information

This chapter covers the following topics: Characteristics of roaming Layer 2 roaming Layer 3 roaming and an introduction to Mobile IP

This chapter covers the following topics: Characteristics of roaming Layer 2 roaming Layer 3 roaming and an introduction to Mobile IP This chapter covers the following topics: Characteristics of roaming Layer 2 roaming Layer 3 roaming and an introduction to Mobile IP C H A P T E R 5 Mobility This book covers the major components of 802.11

More information

CS 5480/6480: Computer Networks Spring 2012 Homework 1 Solutions Due by 9:00 AM MT on January 31 st 2012

CS 5480/6480: Computer Networks Spring 2012 Homework 1 Solutions Due by 9:00 AM MT on January 31 st 2012 CS 5480/6480: Computer Networks Spring 2012 Homework 1 Solutions Due by 9:00 AM MT on January 31 st 2012 Important: No cheating will be tolerated. No extension. CS 5480 total points = 32 CS 6480 total

More information