Mapping Mechanism to Enhance QoS in IP Networks

Transcription

1 Mapping Mechanism to Enhance QoS in IP Networks by Sriharsha Karamchati, Shatrunjay Rawat, Sudhir Yarram, Guru Prakash Ramaguru in The 32nd International Conference on Information Networking (ICOIN 2018) Report No: IIIT/TR/2018/-1 Centre for Security, Theory and Algorithms International Institute of Information Technology Hyderabad , INDIA January 2018

2 Mapping Mechanism to Enhance QoS in IP Networks Sriharsha Karamchati CSTAR IIIT Hyderabad India Sudhir Yarram CVIT IIIT Hyderabad India Shatrunjay Rawat CSTAR IIIT Hyderabad India Guru Prakash Ramaguru CVIT IIIT Hyderabad India Abstract The purpose of this research is to explore the possibilities and mechanisms to be followed in order to extend the QoS in the backbone networks. This paper extends the ideas discussed in my previous paper: A Novel Architecture to Enhance Quality of Service in IP Networks [1] explaining the consequences of the proposal and building a model network. Simulated an SDN network using mininet and presented the packet captures depicting the extension of QoS outside the access networks. Key words: Quality Of Service, Backbone Networks, Network Architecture I. INTRODUCTION AND BACKGROUND Quality of Service is used to measure service performance in computer networks. It is used to prioritize among different applications, users or data flows and perform resource reservation control mechanisms.the Service can be to a particular set of users, or a particular data flow or kind of packets. The differentiation in the services can be in terms of packet loss, throughput, bit error rate, jitter, latency etc. It is particularly important to transport traffic that has special requirements or insufficient network capacity, for example, voice over IP (VoIP), IPTV,Online gaming. Most times, these real time multimedia streaming applications require fixed bit rate and are delay sensitive. Typical issues which arise while the packet travels from origin to destination are drops,throughput, latency, jitter and errors. In the current day internet, the bandwidth and resource requirement varies from application to application. With new applications taking over the internet, video and audio calling over IP networks have become the most routinely used features of the applications. These features have necessities such as high bandwidth, for example skypes bandwidth requirement is as follows. The table I provides the minimum download and upload speeds required, as well as the recommended speeds for best performance. If you are signed in to Skype but not making any calls, Skype will use on average 0-4kbps. When you make a call, Skype will use on average between kbps 1. Call type Minimum download/upload Recommended speed download/upload speed Calling 30kbps / 30kbps 100kbps / 100kbps Video calling 128kbps / 128kbps 300kbps / 300kbps /Screen sharing Video 400kbps / 400kbps 500kbps / 500kbps calling(highquality) Video calling(hd) 1.2Mbps / 1.2Mbps 1.5Mbps / 1.5Mbps Group video(3 512kbps / 128kbps 2Mbps / 512kbps people) Group video(5 2Mbps / 128kbps 4Mbps / 512kbps people) Group video(7+ 4Mbps / 128kbps 8Mbps / 512kbps people) TABLE I DOWNLOAD / UPLOAD SPEEDS II. ARCHITECTURE: Real Time applications are fast growing in the internet. From the previous sections it is pretty evident that an improved QoS is needed for a packet in these applications. This can be done by 1) Enhancing the existing QoS by using better resources and refined algorithms. 2) Exploring the extension of QoS into those areas where it was not available previously. The paper proposes an architectural solution to the second approach.. In general the QoS is provided within an access network because 1) QoS provider has knowledge about the network parameters. 1

3 2) resources can be allocated in an structured manner based on the priority of the packets. 3) The SLAs can be defined in a systematic manner between the service provider and the customer. The architectural solution presents a method to provide QoS across the different access networks.a few infrastructure changes will be needed for this implementation, as layer - 3 devices have to be installed in order to mark the packets in the backbone network.the possible methods and their consequences are also discussed. A network consists of various access networks which are diverse in terms of QoS provisions. The packets traverse across different access networks which have their own network conditions and QoS. These differences across the access networks can be in terms of the protocols used for communication, bandwidth capacity of the link through which the packet has traversed, the delays suffered by the packet and other services provided to the packet. Once the packet traverses beyond its access network, it enters into the backbone network. Since the packets in the backbone network come from various access networks, the services provided to each of the packets within its access network have to be taken into consideration in order to provide the QoS in the backbone network.. However, the ToS or DSCP bit is set in the packet for an access network, based on which the QoS provisions are made to the packet, there could be other services provided to the customer based on the availability of resources in that particular access network. Other than the ToS/DSCP bit which is set to the packet in its access network, there could be other parameters which affect the packets flow such as bandwidth, bit error rate, packet loss and packet delay variation. 1) Availability : Fig. 1. QOS Parameter Connectivity : the physical connectivity between the network elements Functionality : proper functioning of the network elements in the network management layer 2) Loss 3) Delay 4) Utilization Service providers and the customers: In the current day telecommunication market place, various service providers and customers need SLAs [2]. Service providers can be of three types, Network Service Provider (NSP), Internet Service Provider (ISP) and Application Service Provider (ASP). Consumers can also be of three types individual, organization or enterprise. SLA Provisioning and SLA monitoring are the most important processes in the network management layer. Network service can be of various kinds such as leased line service, IP-VPN service, xdsl services, Frame relay service, etc. QoS Parameters represent the quality of service given to the customer. It should be easy for the customers to understand the degree of assurance of the service provided. Generic QoS parameters which are required in the network service are availability, delivery, latency, bandwidth, MTBF (Mean Time Between Failure) and MTRS (Mean Time to Restore Service). The first four parameters could be mapped to the Network Performance Metrics(NPMs) as they are technology specific and could be easily measured, whereas MTBF and MTRS cannot be mapped to NPMs. NPMs can be categorized into four types, which are Fig. 2. NPMs A. Mapping between QoS parameters and NPMs Mapping between QoS parameters and NPMs can be of two types :- measurement mapping and evaluation mapping. In the figure 3, MTBF and MTRS are the QoS parameters which cannot be directly measured from the NPMs.herefore they are computed by the service providers when there is a violation of NPMs. Evaluation mapping is used to verify QoS parameters from the measured NPM values. For example, the availability qos parameter relates to connectivity and functionality in the network service. Therefore availability can be evaluated based on the downtime of the network elements. The measurement and evaluation mappings have to be generalized, as the QoS parameters may vary depending on different NPMs, with various service providers and customers.

4 Fig. 3. Measurement mapping Fig. 4. Evaluation Mapping Generic function of mapping between QoS parameters and NPMs can be defined using mathematical sets and functions. Let there be three sets Q, N and E. Q represents set of QoS parameters N represents set of NPMs E represents of set of evaluation functions. Fig. 5. Function Set 2 N is the power set of N. Measurement mapping m(x) can be defined as the relationship between set 2 N and set Q. Evaluation mapping n(x) can be defined as the relationship between set 2 N and set E. B. Introduction of QoS aware routers In general, a sub network does not have the information such as resource allocation or routing information of the other sub network. Therefore provisioning of QoS is restricted within the access network. Hence this paper proposes a QoS aware router to eliminate the restriction by extending the services provided to the packet into the backbone network. It is typically a layer- 3 device, but a layer-2 device which can modify QoS related fields such as ToS/DSCP of a packet can also be used. The QoS bit of the packet in the backbone network has to mapped to a particular value based on which the further services are provided. This mapping can be designed in various possible ways, 1) A control message is sent to these QoS aware routers which change the QoS of the packet according to the requirement of that traffic. 2) The packet itself contains a value according to which the QoS is mapped.the optional fields in the packet can be used to store these values. The QoS aware routers(qa) may upgrade or downgrade the priority of the packet as per the requirement. The placement of such routers is a key criteria as it involves computation. In general, the backbone network contains switches and the processing involved is very less, in order to keep transmission fast in a backbone network. C. Example of traffic from one network to another: Consider a packet traversing from a network A into another network B. In order to accommodate the QoS provision which was assured for the packet, QoS has to be provided in network A as well as in the network B. But the network A and network B could be different at various levels such as protocol followed, resources available etc. Hence we need a mapping between the QoS parameters from one network to another. For example, in a particular network the QoS is guaranteed at the Bit Error Rate level. But when the packet traverses into another network, it can be mapped to packet loss and can assure QoS based on the packet loss. For example, in a particular network the QoS is guaranteed at the Bit Error Rate level. When the packet traverses into another network, which provides services to the packet in terms of packet loss, the QoS assurance has to be given in terms of packet loss. Hence there should be a mapping between the QoS provisioning in terms of Bit Error Rate and packet loss in order to assure QoS to a packet throughout its traversal. D. IP vs ATM In an IP network, there is a priority bit set in the packet and there is no parameter specification such as bandwidth Whereas in an ATM network minimum or maximum bandwidth would be specified. Suppose if an ATM network is connected to an IP network, in general IP is translated to best effort of ATM. But when we carry out QoS mapping, additional services can be guaranteed. The services guaranteed are supported by the application layer and not the IP layer. Since there is no end to end ATM network, it is rarely used as the edge network and mostly as a backbone network. If IPv6 packet is mapped to an ATM network, it would be easier for ATM to handle and map as the ATM has more services compared to that of IPv6. E. Issues architecture is trying to address: The research proposes architecture which tries to solve the QoS provisioning issues when a packet traverses from one network to another. The QoS can be mapped and carried across

5 networks that have different protocol etc. Though both the networks provide QoS and have the required infrastructure, the way QoS is provided might not be compatible and the architecture proposed provides the mapping which could be used in those scenarios. As we explore the possibility of introduction of QoS into the backbone network, there could be multiple constraints as the installation of QoS aware routers requires change in the existing infrastructure. F. When do we need this architecture This architecture can be provided based on the SLA between the service provider and the customer. Since it involves additional computation and resources, we need to identify the situations and scenarios where the architecture would be needed and to what extent it would be needed. The mapping algorithm varies across the networks in which the packet traversal takes place. If a packet traverses into the network B from network A and if both A and B have similar QoS provisioning, the mapping algorithm has no role to perform. The similarity factor between the networks can be decided based on the QoS related network parameters. The evaluation of similarity factor can be left for future research. There could be two cases possible a)when a packet does not require the mapping and b)when the customer is not subscribed to the mapping service. In case (b), the packet can bypass the QoS aware routers and follow best effort path. Whereas in case (a), lets assume the packet traverses from network a1 - a2 and then to a4. Here a1 and a2 are of similar QoS requirements and hence there is no need of mapping. But when the packet goes into the a4 network, it needs mapping. The QoS requirements,based on which the similarity of the networks is defined, are not specific to the packet, but rather to the full network architecture it traverses in. The QoS requirement in a particular network can either be inserted into the packet at the gateway or the edge devices, if a network does not want to expose the internal implementation details to the backbone network. The treatment can vary from connection to connection or session to session, rather than at a packet level. For example, in an ATM network the mapping can be based on the connection id, and similar mapping algorithm is applicable for all the packets belonging to that particular connection, thereby reducing the overhead of re evaluating the mapping parameters for each of the packets. G. Issues with introduction of such an architecture Security will be of major concern since the treatment of the packets is based on what information is put into the packet at the edge devices. The information put into the packet should be authenticated, verified and should comply with the SLA. For example, a malicious edge router might upgrade the packet priority to a very high value, hence the backbone provides the highest priority to the packet though it is not defined in the SLA and might cause degradation of services to the other flows. There could be multiple other drawbacks of the architecture proposed, the prime one being requirement of change in the network infrastructure. Since the QoS aware routers have to be installed at particular places in a network, the complete network topology which has to be taken under consideration, has to be clearly defined. The additional overhead of prioritizing the flows after considering the network parameters might cause delays and can affect the performance. Hence the optimization of the mapping algorithms has a significant scope for research. There could also be a case where the QoS of the packet gets degraded due to the unavailability of resources or QoS provisioning in the backbone network. Since there could be a compromise of QoS in the access networks assuming upgradation of QoS in the backbone network/ There could be a case where the QoS of a packet in the access network is compromised assuming the upgradation of the QoS in the backbone network. But if the backbone network fails to upgrade the QoS due to unavailability of resources, the overall QoS of the packet is degraded.hence the availability and allocation of resources has to be known in prior in a large scale which could affect the scalability of such an architecture. To address some of these issues, software defined networks(sdn) would play a key role. SDN technology is an approach to computer networking which allows network administrators to programmatically initialize, control, change and manage network behaviour through open interfaces and operate at a higher abstraction level. It was introduced to address static nature of traditional networks which do not support the dynamic and scalable computation. This is achieved through decoupling of SDN controller or control plane (which make decisions regarding the propagation of traffic) from data plane (which constitutes of systems that forward traffic to the respective destinations). Therefore in case of an SDN, there would not be significant infrastructure changes. Few modules have to be installed into the SDN controller which maps the packets based on the QoS provided for the packet or flow in its access network. It also considers the QoS related network performance metrics of that access network and assigns the QoS bits (ToS or DSCP). According to these bits the treatment of those respective packets is provided in the backbone network. Modifications to the flow entries have to be made based on the mapping algorithm. The model topology, the working of the proposed architecture and the mechanism is implemented on mininet and is explained in detail in the next section. III. MAPPING AND SIMULATION In order to provide QoS to a packet when it traverses from one network to another, various parameters of the packet as well as the networks through which the packet traverses has to be taken into consideration. These include ToS of the packet in the source network,the protocols followed in the networks, control flags of the packet etc. Bandwidth and bit error rate

6 would also be an important criteria to understand the QoS provided in a network. Hence the proposed mapping box assigns a QoS value to the packet based on these parameters. This value is used to provide the services to the packet in the backbone network. The flow of the packets would be as shown in figure 6 The packets further traverse to router E with the assigned QoS bit. The activity at the router E explains the behaviour of the packet as per their assigned QoS. Consider the below figure 7 Fig. 6. Mapping Flow chart The mapping box can be treated like a black box which takes the set of packets from diverse networks and their QoS related parameters as input. It then assigns the QoS value according to the parameters and outputs the packets into different streams. Based on the streams through which the packet traverses, QoS is provided to the packet in the backbone network. When the desired QoS is not provided to the packet in its access network, a flag is included along with the other parameters which act as input to the mapping box. The flag indicates if the desired QoS is delivered to the packet in its access network. Based on the flag, the mapping is performed to upgrade or downgrade the packets QoS in the backbone network to ensure the expected delivery of QoS to that particular packet. Our router would have very similar components compared to a DiffServ router, but the criteria of classification would also include network parameters such as Bandwidth and Bit error rate in order to differentiate the network. The simulation run resulted in a model network which illustrates the functioning of the proposed architecture and the QoS aware router. A. SIMULATION The network topology for simulation consists of one QoS aware router to which the three gateway routers of three access networks(a1,a2 and A3) are connected. This QoS aware router is again connected to the router E. The topology is simulated to model a network in which the packets traverse from the access network into the backbone network. The packets are provided with QoS inside the access networks and the proposed architecture extends the services into the backbone network. In our simulation, let s assume the access networks to consist of a host(hx) and another local network (Nx). The packets have an existing QoS provided inside each of the access networks. The packets traverse into the backbone network through the edge routers. The QoS will be assigned to each of the packets at the QoS aware router. The assignment is based on the QoS of the packet in its access network and other network performance metrics. Fig. 7. Simulation In our simulation, the packet traversing from the access network A, through the Router-A has a QoS bit value of 1. And the packets from the network B and C have their QoS bit values as 3 and 5 respectively. When the packets arrive at the Router D, the QoS bits would be modified to QoS-A, QoS-B and QoS-C respectively. QoS-A is the output of a calculation made based on the network parameters of A which are related to QoS and existing QoS bit of the packet.there could be other parameters like SLA included in the computation as well. The SLA is an important consideration during the computation as the services are provided to the user according to the SLA. Hence factors related to the SLA influence the QoS-A to a large extent. There could be a possible scenario where the guaranteed QoS in the access network is compromised for lack of resources. In that case, the QoS has to be upgraded in the backbone network in order to compensate for the loss in services in the access network. To implement such a service, flag has to be set when there is a variation in the services provided to the packet in the access network. so that it can be upgraded or degraded in the backbone network accordingly. The flag can also represent to what extent the service level has been varied. Therefore the QoS-A can be written as a function of SLA factor, Existing QoS in the access network, network parameters and the flag. QoS-A = f(sla,flag,qosa,npm). B. Experimental Results The simulation of the above mentioned mapping is carried out in an SDN environment using mininet. The connection for the simulation is mentioned as below. h1r1 is connected to A. h1r2 is connected to B. h1r3 is connected to C. bh1 is connected to E.

7 A,B and C are in turn connected to D, which is connected to E. A controller is connected to each of these entities. In an SDN, all the devices are termed as switches. Fig. 9. A to E before the mapping Fig. 8. Experimental Design The packets which traverse from Switch A have the ToS bit value set as 4, packets from Switch B have ToS as 8 and those from Switch C as 10. As per our proposal, switch D is the special router which maps the QoS bits based on the source network. When the packets traverse from the switch D to switch E, the packets whose ToS bit is 4 is mapped to 1, packets having ToS bit 8 is mapped to 2 and the packets having ToS bit 10 are mapped to 3. For simplicity, we assume the mapping is one to one between the ToS from A,B and C and also for those that traverse out of D. These packets are put into 3 different queues based on the ToS bit at E. There would be variations in the services provided to each of the queues at E such as bandwidth capacity of the queue etc. The packets were captures using wireshark during their different phases of the traversal. The QoS bit of the packets during those phases is presented below. The DSCP value of the packet from the router A was set to 4 as per the capture shown in Figure 9, and is modified at the QoS aware router(d) to 1 based on the source network. The packet traversing from D to E as shown in the Figure 10 has DSCP value as 1. The DSCP value of the packet from the router B was set to 8 as per the capture shown in Figure 11, and is modified at the QoS aware router(d) to 2 based on the source network. The packet traversing from B to E as shown in the Figure 12 has DSCP value as 2. The DSCP value of the packet from the router C was set to 10 as per the capture shown in Figure 13, and is modified at the QoS aware router(d) to 3 based on the source network. The packet traversing from C to E as shown in the Figure 14 has DSCP value as 3. Fig. 10. A to E after the mapping Fig. 11. B to E before the mapping : IV. C ONCLUSION AND F UTURE W ORK In this paper,we proposed a mapping mechanism and simulation for the architecture proposed in the previous paper: A Novel Architecture to Enhance Quality of Service in IP Networks. Used mininet to build the network topology and wireshark for capturing the packets. Consequences of this implementation, along with the example scenarios in which the architecture will be applicable is also discussed.

8 Since the usage of software defined networks(sdn) has increased in the recent times, the implementation of the proposed mechanism in the SDN can be explored in future. The simulation presented in the paper can be used as a start point. R EFERENCES [1] S. Karamchati and S. Rawat and V. Varma, A novel architecture to enhance Quality of Service in IP networks, 2017 International Conference on Information Networking (ICOIN). [2] Hyo-Jin Lee and Myung-Sup Kim and James W. Hong and Gil-Haeng Lee, QoS Parameters to Network Performance Metrics Mapping for SLA Monitoring, 2013 Fig. 12. B to E after the mapping: Fig. 13. C to E before the mapping Fig. 14. C to E after the mapping A. Future Work The implementation of the proposed architecture requires significant changes in the infrastructure.hence all possible ways to reduce computation and other infrastructural changes required have to be explored.the scenarios in which the proposed architecture can be applied have to be explored. The algorithm used in the mapping box has scope for significant research. The impact factor for each of the parameters taken into consideration for classification can be derived by conducting experiments.