A Strategy of CDN Traffic Optimization Based on the Technology of SDN

2016 International Conference on Electronic Information Technology and Intellectualization (ICEITI 2016) ISBN: 978-1-60595-364-9

A Strategy of CDN Traffic Optimization Based

on the Technology of SDN

Yirong Wang, Hongkai Wang, Botao Yu and Yue Ma

ABSTRACT

Modern Content Delivery Network(CDN)[1,2] by caching and scheduling strategy to reduce user-perceived latency, because CDN can schedule user to the CDN cache node which closest to. At the same time, this strategy can reduce the data flow which has to be sent back to the source station, and decrease the calculation pressure of source station. For some content which is dynamic and cannot be cached, the current acceleration approach is to create a GRE tunnel between the CDN nodes, using the static route scheduling dynamic data flow, improve the speed of data flow which back to the source station. It has been a recent trend of CDN to separate the control flow and data flow through technical, in order to change traditional dynamic/static content acceleration model, to optimize the CDN traffic.

INTRODUCTION

By adding a layer in the existing Internet intelligent virtual network, pushing the contents to the virtual network node which is most close to the user, CDN allows a user to obtain the content from the nearest CDN node, so as to solve the congestion problem of internet network, and improve the response speed of the user to access the website, make the IP network into a high efficient, reliable, intelligent network from which was disordered, inefficient and unreliable originally.

In the SDN architecture, the control and data planes are decoupled, network intel ligence and state are logically centralized, and the underlying network infrastructure is abstracted from the applications. Traditional Internet architecture is distributed, each network device has a relatively independent of the operating system and control level, exchange information and data between equipment by distributed Internet protocol. After adopting SDN architecture, we can do the centralized scheduling based on global network resources. Under the environment of SDN, traffic engineering[5] can bring exciting increases for network performance, the existing successful cases, such as Google's B4 system [7]has used dedicated SDN equipment to trans formed the network of data center into SDN completely, this project made the network utilization be promoted to nearly 100%. After using general SDN equipment, the software definition WAN (Soft WAN, SWAN) system [6] of Microsoft made the network utilization be increased by 60% ~ 70%.

STRATEGY OF CDN TRAFFIC OPTIMIZATION

The Cache Cluster Collaborative Interaction Optimization

For getting the information of contents which were cached in CDN nodes, it is necessary to establish a good communication channel between the vast CDN nodes after CDN constructed to a certain size. Copy content to cache from neighbor node more efficient rather than from the source station, and can save the data traffic for source station. We can improvement for Cache cluster collaborative interaction base on network architecture of SDN:

1．DevelopCDN schedule APP by SDN north interface, all cache information of CDN nodes are stored in the CDN schedule APP.

2．CDN schedule APP can get global traffic information of CDN from SDN controller in real time.

Interaction

Data transmision 1）

2）

3） 4）

5）

6） 7）

SDN Controller

Source Station

CDN node1

CDN node1 SDN Switch CDN Schedule APP

Figure 1. Cache cluster collaborative interaction base on SDN. 

1) CDNnode2 received the content request packets come from user, because the content does not exist in local cache, node 2 have to simulate client to send content request.

2) the content request packets come from node2 arriving at SDN switch the node 2 access to, the switch found that there is no matching flow table item after lookup flow table, and then encapsulate request packet into Packet in message up to SDN controller.

3) SDN controller judge the type of packets after receiving the message in order to send these packets to the corresponding CDN schedule APP.

4) CDN schedule APP judge the source IP of these packets is belong to node2, and lookup the cache information summary for finding out the node which have cached the contents node2 need. If there are multiple results can be matched in summary, CDN schedule APP will provide the node which have best network condition in this moment from the matching results, such as node 1.

5) CDN schedule APP send Flow-mod message to SDN switch.

Traffic Scheduling Based on the Quality of Nodes Bandwidth

This paper presented a CDN traffic scheduling optimization strategy based on the node of the quality of the bandwidth. Path quality detection module can obtain more CDN links indicators, such as delay, jitter, packet loss rate, etc. The process is as follows:

1.At the beginning of the CDN construct

1) SDN Controller obtain the topology information of global network, connected network forward equipment by automatic or manual.

2) Path quality detection module detect link quality in turn by traversing all path in CDN.

3) Path quality detection module report the detection data to APP. 2.User requests resources

1) After receiving the message of user request resource SDN controller send the packet to corresponding CDN scheduler APP by the type of packet.

2) APP match the link quality table, calculate the optimal business path between user and a CDN cache node, then the bandwidth and priority information be unified recorded in user forwarding table as forwarding strategy.

3) APP send Flow-mod message to SDN switch. 3.In the process of running

1) APP monitors the quality of all links in the network, and update the entire network link - quality table.

2) Forward equipment reports flow data based on user information or user business to SDN controller according to a specified period.

3) APP records user business traffic in statistics table. 4.Whenquality degradation appeared on a single link

1)The weighted score of delay, jitter and packet loss rate is use for judgment method of deterioration in the quality.

2) APP generated the scheduling strategy according to the user's priority and business priority, and first we performed user's priority.

3) APP sent the computation to SDN controller, SDN controller generate forwarding flow table and sent it to SDN switch.

Dynamic Content Acceleration Based on The Technology of SDN

This paper proposed a dynamic content acceleration strategy based on the technology of SDN.

Bandwidth priority weighting

module

User CDN

Back to the source tunnel optimization module Tunnel database management module Topology information gathering module SDN Gateway CDN characteristic information back to source station Dynamic flow back to source station Dynamic flow Back

to source station abstract Flow group information

Bandwidth allocation function

Tunnel and tunnel group information

Topology and link bandwidth information

Traffic scheduling operation CDN node topology

information

Node port

state change Traffic scheduling operation

Figure 2. The create process of SDN acceleration tunnel.  

1. Dynamic flow back to source station abstract sent characteristic information of the flow to bandwidth priority weighting module.

2. Input the result to the module called back to the source tunnel optimization module.

3. At the same time, back to the source tunnel optimization module received the CDN node topology information reported by SDN gateway after topology information gathering module extracted, the CDN node topology information is another input for optimization algorithm.

4. Finally the back to the source channel optimization module according to the result of TE optimization algorithm to decide the back resource station flow will use which tunnel and tunnel group.

5. Tunnel and tunnel group information will continue to be input into the tunnel database management module, tunnel database management module and out the flow schedule operators through SDN gateway.

6. TE optimization algorithm output tunnel group information for different business, control the business flow with different outer tunnel encapsulation, so as to control the bandwidth allocation of dynamic flow.

collaborative interaction between CDN nodes, such as IC, HTCP, Cache Digest[8],Cache Pre-filling [9]and so on.

Traffic Scheduling Based on the Quality of Nodes Bandwidth: Traffic engineering based on SDN is the cutting-edge technology in researches of traffic scheduling based on bandwidth quality in the present. SDN is applied on telecom operator’s backbone traffic scheduling is inspired by the Google B4 project at the earliest. Google have long noticed the value of SDN technology for the Internet data center, as early as in 2009, Google vigorously working in SDN/Open Flow exploration/practice just contact SDN/Open Flow concept.

The CDN based on the SDN technology: Researchers put forward ALTO agreement in 2011, ALTO provide the interface for changing network status, realize the flow optimization in SDN architecture according to this API.

CONCLUSION

Reference SDN successful application in traffic engineering technology, optimize the CDN flow, through the centralized scheduling function of SDN controller, realized the link quality and bandwidth utilization detected and collected automatically, we can created GRE tunnel automation on-demand, and create the forwarding path automatically. Develop CDN scheduling APP to realize global flow schedule function according to the north interface by SDN controller providing, schedule strategy is constructed by the detection results of path quality detection module and the information of the priority of the data traffic; CDN dynamic content accelerate based on SDN realized manager route and tunnel automatically, and can choose the optimum route in the situation of multipath, reduce the effects of the default routing congestion delay when busy.

REFERENCES

1. CDN networks Inc. http://cdnetworks.com/.

2. Content Delivery Networks Interconnection.http://tools.ietf.org/wg/cdni/.

3. Weifeng Zhang, 2014, Depth Resolution of SDN, Beijing: Publishing House of Electronics Industry, pp. 35-42.

4. Jain S., Kumar A., Mandal S., 2013, B4: Experience with a globally-deployed software defined WAN, ACM SIGCOMM Computer Communication Review, 43(4): 3-14.

5. Aw Duche D., Chiu A., Elwalid A., 2002, Overview and principles of Internet traffic engineering, RFC3272, pp, 28-36.

6. Hong C.Y., Kandula S., Mahajan R., 2013, Achieving high utilization with software-driven WAN, ACM-SIGCOMM Computer Communication-Review, 43(4): 15-26.

7. Danana E., Hassidim A., Kaplan H., Kumar A., Mansour, Y. Raz D. and Segalov M., 2012, Upward Max Min Fairness, INFOCOM, March, 2012: 837-845.