Bilal Real Time LAb 4

7/29/2019 Bilal Real Time LAb 4

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ELEC6181

REAL TIME MULTIMEDIA COMMUNICATIONS OVER INTERNET

EXPERIMENT # 4

SUBMITTED BY

Bilal Akhtar

5208386


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Introduction

Policing and Shaping Overview

Cisco IOS QoS offers two kinds of traffic regulation mechanisms: the rate-limiting feature of committedaccess rate (CAR) for policing traffic, and Generic Traffic Shaping (GTS) for shaping traffic. You can

deploy these features throughout your network to ensure that a packet, or data source, adheres to a

stipulated contract and to determine the QoS to render the packet. Both policing and shaping

mechanisms use the traffic descriptor for a packetindicated by the packet's classificationto ensure

adherence and service.

Policers and shapers usually identify traffic descriptor violations in an identical manner. They usually

differ, however, in the way they respond to violations, for example:

A policer typically drops traffic. (For example, CAR's rate-limiting policer will either drop thepacket or rewrite its IP Precedence, resetting the packet header's type of service bits.)

A shaper typically delays excess traffic using a buffer, or queueing mechanism, to hold packetsand shape the flow when the data rate of the source is higher than expected. (For example, GTS

uses a weighted fair queue to delay packets in order to shape the flow.)

Traffic shaping and policing can work in tandem. For example, a good traffic shaping scheme should

make it easy for nodes inside the network to detect misbehaving flows. This activity is sometimes called

policing the flow's traffic.

The Token Bucket mechanism is used by the policer or shaper to measure traffic and is discussed here.

Token Bucket as a traffic measurement instrument

A token bucket is a formal definition of a transfer rate. It has three components: burst size, mean rate,

and time interval (Tc).

Mean rate (committed information rate (CIR)): It specifies how much data, on average, can besent per time unit.

Burst size (Conformed Burst) Also called the Committed Burst (Bc) size, it specifies in bits perburst how much can be sent within a given unit of time to not create scheduling concerns. The

size of the Token Bucket is equal to Bc.

Time interval: Also called the measurement interval, it specifies the time quantum in secondsper burst.Although the mean rate is generally represented as bits per second, any two values may be derived from

the third by the relation shown as follows:

Mean rate = Burst size /Time interval


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By definition, over any integral multiple of the interval, the bit rate of the interface will not exceed the

mean rate. The bit rate, however, may be arbitrarily fast within the interval.

In a token bucket, tokens are put into the bucket at a certain rate. The bucket itself has a specified

capacity. If the bucket fills to capacity, newly arriving tokens are discarded. Each token is permission for

the source to send a certain number of bits into the network. To send a packet, the regulator must

remove from the bucket a number of tokens equal in representation to the packet size. If not enough

tokens are in the bucket to send a packet, the packet either waits until the bucket has enough tokens or

the packet is discarded or marked down. If the bucket is already full of tokens, incoming tokens overflow

and are not available to future packets. Thus, at any time, the largest burst a source can send into the

network is roughly proportional to the size of the bucket. Note that the token bucket mechanism used

for traffic shaping has both a token bucket and a data buffer, or queue; if it did not have a data buffer, it

would be a policer.

For traffic shaping, packets arriving that cannot be sent immediately are delayed in the data buffer. For

traffic shaping, a token bucket permits burstiness but bounds it. It guarantees that the burstiness isbounded so that the flow will never send faster than the capacity of the token bucket plus the time

interval multiplied by the established rate at which tokens are placed in the bucket. It also guarantees

that the long-term transmission rate will not exceed the established rate at which tokens are placed in

the bucket.

How a Traffic Policer or Shaper Works

A traffic policer or shaper examines traffic received on an interface or a subset of that traffic selected by

access list criteria. It then compares the rate of the traffic to a configured token bucket and takes action

based on the result. For example, it will drop the packet or rewrite the IP precedence by resetting the

type of service (ToS) bits.

A token bucket measurement is used to measure traffic. Tokens are inserted into the bucket at the

committed rate (CIR). The depth of the bucket is the burst size (Bc). Traffic arriving at the bucket when

sufficient tokens are available is said to conform, and the corresponding number of tokens are removed

from the bucket. If a sufficient number of tokens are not available, then the traffic is said to exceed.


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Matching Criteria

Traffic matching identifies the traffic of interest for rate limiting, precedence setting, or both. It can be

configured with one the following parameters:

Incoming interface

All IP traffic

IP precedence (defined by a rate-limit access list)

MAC address (defined by a rate-limit access list)

IP access list (standard and extended)

Traffic shaper/policer provides configurable actions, such as send, drop, or set precedence when traffic

conforms to or exceeds the rate limit.

Conform and Exceed Actions

A policer/shaper uses a token bucket. Once a packet has been classified as conforming to or exceeding a

particular rate limit, the router performs one of the following actions on the packet:

TransmitThe packet is sent.

DropThe packet is discarded.

Set precedence and transmitThe IP Precedence (ToS) bits in the packet header are rewritten. The

packet is then sent. You can use this action to either color (set precedence) or recolor (modify existing

packet precedence) the packet.

Continue The packet is evaluated using the next rate policy in a chain of rate limits. If there is not

Another rate policy, the packet is sent.

Set precedence and continueSet the IP Precedence bits to a specified value and then evaluate the

next rate policy in the chain of rate limits.

Traffic Engineering Using Policy Based Routing

Routing in IP network is usually based on a packets destination IP address. Routing based on other

information carried in a packets IP header is possible by using Policy Routing.

For traffic destined to a particular server, you might want to send traffic with a precedence of 3 on a

dedicated faster link than traffic with a precedence of 0. Though the destination is the same, the traffic

is routed over a different dedicated link for each IP precedence. Similarly, routing can be based on

packet length, source address, a flow defined by the source destination pair and TCP/UDP ports, ToS

/precedence bits, and so on. This flexible routing is commonly referred to as Policy Based Routing.

Policy based routing is not based on any dynamic routing protocol, but it uses the static configuration

local to the router.

Policy Based Routing Specification

Policy based routing is applied to incoming traffic. All packets received on an interface with policy based

routing enabled are passed through a route map. Based on the criteria defined in the route map,

packets are forwarded to the appropriate next hop. In this case, instead of routing based on the


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destination address, policy based routing allows you to determine and implement routing policies to

allow or deny paths based on the following:

The identity of a particular end system The application being run

The protocol in use The size of packetsThe route map statements used for policy based routing can be marked as permit or deny. If the

statement is marked as deny, a packet meeting the criteria will be sent using the destination based

routing. If the statement is marked as permit and the packet meets any of the match criteria, the

corresponding set statement will be applied. If no math is found in the route-map, the packet will be

sent using destination based routing.

Experiment 4: Traffic Policing, Shaping and Engineering

Complete the following experiment to configure traffic policing, shaping and engineering in a network.

In this experiment, students will work in the following groups:

Group 1: R25-1 & R45-1

Group 2: R25-2 & R45-3

Group 3: R25-3 & R45-2

Groups should start each task by coordination of the instructor. All groups should start each task at the

same time. Whenever you obtain performance diagrams, you should capture and present them in your

report.

Objective

In this lab experiment you will complete the following tasks:

Configure Traffic Policing/Shaping Configuring Traffic Engineering by using Policy based Routing

Command List

You can find the required command in each step.

Setup

Check the router configurations. OSPF routing should be enabled on all routers and you should be able

to access all router interfaces and hosts in the network. All router interfaces should be up in both

physical and data link layers.


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Task A: Configure network topology

Step 1 Configure serial interfaces speed as 256Kbps and queuing as FIFO.

Note: To configure an interface speed, you should change both the clock rate and interface bandwidth

as it was done in Lab Experiment 1.

Rx-x#configure terminal

Rx-x(config)#interface serial0/x x= 0, 1

Rx-x(config-if)#clock rate 256000

Rx-x(config-if)#bandwidth 256

Rx-x(config-if)#^z

Task B: Check network topology

Complete the following steps.

Step 1 Check the routing paths from your router to all the other routers and write down the results in

the following table. You should use the following command:

Source router Destination router Path

R25-3

R25-2 10.0.15.6-->10.0.15.14 (2 Hops)

R25-3 10.0.15.10 -->10.0.15.25 (2 Hops)

R45-1 10.0.15.16 (1 Hop)

R45-2 10.0.15.10 (1 Hop)

R45-3 192.168.20.65

Task C: Monitor network performance

Step 1. Using IPM, configure the following collectors and operations. All collectors startup time should

be defined as on demand.

Collector

Parameters

Timeout Sample

Interval

Destination

Port

Request

Payload

Packet

Interval

No. of

Packets

Jitter

Threshold

Voice-x-x 5000 10 UDP16400 160 20 150 250

Video-x-x 5000 10 UDP50505 1024 100 50 250

FTP-x-x 9000 10 TCP 21

R25-1:ftp://192.168.20.68/atapi.exe

R25-2:ftp://192.168.20.84/atapi.exe

R25-3:ftp://192.168.20.100/atapi.exe

Note: Do not start collectors in this step.
ftp://192.168.20.68/atapi.exeftp://192.168.20.68/atapi.exeftp://192.168.20.68/atapi.exeftp://192.168.20.84/atapi.exeftp://192.168.20.84/atapi.exeftp://192.168.20.84/atapi.exeftp://192.168.20.100/atapi.exeftp://192.168.20.100/atapi.exeftp://192.168.20.100/atapi.exeftp://192.168.20.100/atapi.exeftp://192.168.20.84/atapi.exeftp://192.168.20.68/atapi.exe


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Step 2 Start Voice, Video and FTP collector in IPM and check the traffic delays for a period of 5 minutes.

Then capture real-time diagrams and stop the collectors.

FTP OUTPUT

VIDEO OUTPUT


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VOICE OUTPUT

Task D: Configure traffic policing

Step 1 Configure traffic policing to mark packets with the following DSCP values:

Mark FTP traffic up to 16Kbps with DSCP=2 and for more than that with DSCP=1 Mark Video traffic up to 48Kbps with DSCP=4 and for more than that with DSCP=3 Mark Voice traffic up to 32Kbps with DSCP=6 and for more than that with DSCP=5

The following access lists can be used to separate each traffic type (conditioning):

Rx-x(config)#Access-list 130 permit tcp 192.168.20.84 0.0.0.15 any eq ftp

Rx-x(config)#Access-list 130 permit tcp 192.168.20.84 0.0.0.15 eq ftp-data any

Rx-x(config)#access-list 140 permit udp any any eq 16400Rx-x(config)#access-list 150 permit udp any any eq 50505

For traffic policing, the following commands should be executed on the specified routers:

R25-x(config)#interface serial0/0

R25-x(config-if)#rate-limit output access-group 130 16000 2000 2000 conform-action set-dscp-continue

2 exceed-action set-dscp-continue 1


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R25-x(config-if)#rate-limit output access-group 150 48000 2000 2000 conform-action set-dscp-transmit

4 exceed-action set-dscp-transmit 3



R25-x(config)#interface serial0/1



R25-x(config-if)#rate-limit output access-group 150 48000 2000 2000 conform-action set-dscp-transmit

4 exceed-action set-dscp-transmit 3



Task E: Monitor Network Performance

Step 1 Start Voice, Video and FTP collectors and enter the following command to check the packet

marking:

FTP OUTPUT


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VIDEO OUTPUT

VOICE OUTPUT


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R25-x#show interface serial 0/x rate-limit

Check the command output and append it to your report. Try to discuss various fields in the

output. Stop the traffic collectors after you finish this step.

Serial0/0

Output

matches: access-group 130

params: 16000 bps, 2000 limit, 2000 extended limit

conformed 0 packets, 0 bytes; action: set-dscp-continue 2

exceeded 0 packets, 0 bytes; action: set-dscp-continue 1

last packet: 6984232ms ago, current burst: 0 bytes

last cleared 00:05:36 ago, conformed 0 bps, exceeded 0 bps



conformed 0 packets, 0 bytes; action: set-dscp-transmit 4

exceeded 0 packets, 0 bytes; action: set-dscp-transmit 3









R25-3#show int s0/1 rate-limit

Serial0/1

Output









conformed 540 packets, 570240 bytes; action: set-dscp-transmit 4

exceeded 357 packets, 376992 bytes; action: set-dscp-transmit 3




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Results Explanation

In these results, matches field shows that what access list is applied on this interface. Params field

tells us what is the data rate limit applied in that access group. Conformed field tells how many

packets have conformed to the data rate limits and exceeded field tells how many packets have

exceeded the limit. Action field tells what to do if the packet is conforming or nonconforming. The

Last Packet field tells us that when the last packet was received. Last Cleared field tells us the time

when the counters were last cleared by using clear counter command.

Task F: Traffic Management Configuration

Step 1 In this step, you configure policy based routing to transmit FTP traffic through a different route

compared to the shortest path chosen by OSPF. New paths are shown in the following table.

Source Router Destination FTP

Server

Routers Traversed Routers with Policy

statements

R25-2 WS-25-1 R25-1->R45-2->R45-3 ->R25-1 R25-1->R45-2

R25-3 WS25-2 R25-2->R45-1->R45-2->R25-3 R25-2->R45-1

R25-1 WS25-3 R25-3->R45-3->R45-1->R25-1 R25-3->R45-3

FTP traffic will be selected by using the access lists in step 2. You configure the corresponding route

maps to conduct traffic by using the match and set statements. In match statements, packets are

checked against specific conditions which in this case are the access lists. In set commands, next -hop-

address is specified which is the address of the corresponding interface on the next router in the path.

Enter the following commands in global configuration mode on the corresponding routers specified in

Routers with Policy statements section of above table:

Rx-x(config-route-map)#route-map route-map-name permit 10

For route-map-name we can give any name like group2

match ip address access-list-number

checks ip address with acces list with FTP which acces list 130

set ip next-hop next-hop-address sets the next hop address for this accesslist.

exit


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Step 2 Issue the following commands on the corresponding interfaces to assign route-maps to an

interface. The interface should be chosen as the incoming interface for the preferred traffic

which in this case is FTP.

Rx-x(config)#interface interface-name like ( S 0/1)

Rx-x(config-if)#ip policy route-map route-map-name

Step 3 Execute the debugging command for policy based routing as follows:

Rx-x# debug ip policy

Step 4 Start the Video and FTP collectors that you used in step 2 and answer the following questions:

What messages do you see in your console and what do they mean? How did you use the debug messages to check the accuracy of your route map configurations?

Capture a couple of complete debug messages and append them to your report. Discuss their various

fields.

Note: You can stop debugging messages from appearing at any time by entering the following command

which means undebug all:

Rx-x# u al

Step 5 Obtain delay curves for Voice, Video and FTP for a period of 5 minutes and compare them with

curves you obtained in task C and answer the following questions:


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FTP OUTPUT

VIDEO OUTPUT


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VOICE OUTPUT

Is there any improvement in FTP delay? Why?Ans. Yes, there is definitely some improvements in FTP delay compared to that of the task C and it

ideally that should be the case since, we configured policy for the transfer of FTP traffic. So we can see

slight improvement for FTP delay compared to FTP traffic in task C. In Task F we have an average delay

of 7500 ms while the average delay in Task C was around 6000 ms at the beginning and it jumped to

8000 after one minute.

Is there any improvement in Video delay? Why?Ans. There has been a significant improvement in video delay because of the routing changes that we

implemented in our router. We defined a static route for the traffic which lowered the delay for the

traffic.

Completion criteria

At the end of this lab, you should have obtained the required diagrams for the specified tasks along with

the output of specified commands. We stopped the traffic collectors and copied all the captured

diagrams for our report.


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Conclusion

This experiment was all about configuring traffic policing/shaping and Traffic Engineering in a networkby using Policy based Routing and also monitoring the real-time traffic flow parameters by using IPM.

While performing the experiment, we monitored the network performance for the network with OSPF

routers and the router was configured with 256 Kbps speed and FIFO queuing. Also, we monitored the

network performance after performing traffic policing and we observed that there was not much

difference in the network performance parameters in the two cases. Traffic policing and shaping are

mechanisms used to make sure traffic conforms the service between customers. Dropping and shaping

applied to all packets enter and exit the router, this is done by using token bucket mechanisms. Policy

routing is used to implement traffic engineering and choose optimal routes for different traffic types to

maximize network bandwidth and resources.

We have done operations step by step in our experiment. We have captured the real time statistics

outputs for FTP, video and Voice traffic using usual FIFO technique. Then traffic policing was configured

by first creating an access lists for each separate traffic. Then traffic policing commands were issued on

the serial interfaces using the access lists that were earlier created. It is important to know that, in our

experiment, we applied traffic policing only on 25 series routers and not on the 45 series routers. This is

because only the 25 series machines acts as AG routers , which are generating packets and where traffic

policing would be implemented. The 45 series machines are only forwarding packets and not doing

anything else. Then after Task E we connect the fast Ethernet 0/1 interface and then transmit FTP traffic

using the routes defined in Step F.

We then apply the route-map to the interfaces that we want the particular route map to be

implemented. The interface will first match the access list no. and if its a match and then sets the next

hop as the one given in the table in Task F Step 1. The access-list no. used in this case is for the FTP as is

mentioned in Step 1. In the end we compared the two different graphs obtained from task C and task F

and found negligible differences between them.

The experiment went successful for us. It actually led us to know the various aspects of using access list

and its priority. With the help of DSCP value we came to know how to provide different commands to

proceed with different types of data. Weather it is FTP packet or voice packets.

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