Keywords

1 Introduction

The main application of the computer network domain is the BGP network protocol. The BGP network mainly works out discovering the next routing node independently and following consistent communication rules within a defined domain and among constituent domains. In the BGP inter-domain boundary routing protocol, the routing control is mainly based on the IP address from the communication destination, and the selection of routing path is derived from adjacent routers. In addition, the transparency and intuition of the routing algorithm are not strong [1].

In the SDN framework mode, the main existing problems are reflected in the updating process of routing paths between network domains. The information loss of data stream (namely packets) transmitted between network domains occurs from time to time. The most fundamental reason is the mixed application of traditional network and SDN network technology. The key point of the problem is that the two network management modes have different setting strategies for packet transmission control parameters. In fact, there is no relatively consistent standard for constraint [2,3,4].

Herein, based on the premise of a clear definition of traditional network domain (Route discovery technology which mainly refers to route discovery technology with BGP border Gateway protocol as the core), SDN network domain and BGP-SDN fusion network domain, and based on the application of route update mechanism in SDN network domain, according to the principle of collaborative and consistent interdomain route discovery, The consistency of routing update policies of three types of Interzone’s is constrained to achieve the goal of no packet information loss from the whole mechanism. At the same time, by constructing a standard SDN architecture model and introducing the improved algorithm under its model framework, simulation experiments are carried out from the perspectives of packet loss in data transmission and routing update delay between network domains to verify the reliability and feasibility of the algorithm proposed in this paper.

2 Implementation of the Algorithm in this Paper

To prevent packet loss or network communication interrupt, two key problems need to be solved. One is relatively independent of each domain control server, data packets in asynchronous problem, the other is that the SDN network communication mechanism and BGP do not match the network communication mechanism, which temporarily interrupts the network communication problems (Fig. 1).

Fig. 1.
figure 1

Interzone routing discovery and update policy and packet transmission path design process proposed in this paper.

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As for the effective fusion of SDN network communication mechanism and BGP network communication mechanism, the main solution is to design a highly matched control algorithm between SDN and BGP Network management control policy, focusing on the design of a master control server that can coordinate the control of all inter-domain control servers and synchronize the same task. The main process of the algorithm includes: (1) master control server to send all the network domain “after submit inter-domain routing updates available path” information, the information is changed after routing updates main path information, the information sent by the included in the “all requirements of the network domain has confirmed to receive offers available transmission path to apply for” information, only in the network domain feedback after all complete information, The master server will initiate the next command. In this step, the master controller collects statistics on the SDN network domain, BGP and SDN fusion network domain, and BGP network domain components involved in route updating. (2) The master control server first sends the request of “Enabling interdomain routing to update available paths” to all SDN domains. After receiving the request, the control server in the SDN domain sends the enable instruction to the boundary switch in the domain. The boundary switch completes the parameter update in the data flow table. The in-domain control server feedback the received and completed instructions to the master control server. (3) In the same way as the second step, the master controller sends the request of “Enabling interdomain routing to update available paths” to all BGP-SDN fusion domains, and completes all corresponding instructions with the cooperation of the intra-domain control server and the intra-domain boundary switch. (4) In the same way as in the second step, the master controller sends the request of “Enabling Interzone routing to update available paths” to all BGP network domains, and directs the intra-domain control server and intra-domain boundary switches to complete corresponding instructions.

In the above process, performed by the master control server to set an information exchange round-trip time limit (defined as routing update delay), make sure that the network domain control server and boundary switch when performing routing update instruction, will be the last time the configuration parameter, reset all the data in ensuring accurate routing updates instruction execution at the same time, To a certain extent, it can also improve the synchronization of each operation process. TF−J are mentioned in the algorithm of the concept of routing updates, its exact meaning is according to the prescribed three kinds of a network domain, must first be connected from the source to the target network between domains, independent SDN network domain, BGP - domain SDN fusion, BGP network domain three packet transmission path (so that we can ensure that network system without a cross-domain communication no difference to the target domain), Then, according to the actual status of the network environment, a transmission path that can complete the packet transmission process is constructed according to the sequence of “SDN network domain → BGP-SDN fusion domain → BGP network domain”. In the definition of process flow of source network domain → SDN network domain → BGP-SDN fusion domain → BGP network domain → target network domain must be considered complete. Figure 2 shows the algorithm flow in this paper.

Fig. 2.
figure 2

Flow chart of Interzone routing update algorithm proposed in this paper.

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To realize the above algorithm, the control server set corresponding to the defined network domain set Wsdn, Wbgp, SWsdn, BWbgp and Ws−b needs to be defined first, which can be defined as Fsdn, Fbgp, SFsdn, BFbgp and Fs−b according to the sequence of the above network domain set SWsdn, BWbgp, Ws−b, SFsdn, BFbgp and Fs−b. When the algorithm is implemented, it only needs to define the updated parameters. The parameters before the update can be defined by initializing the updated parameters.

In the master control server, it is also necessary to define some control information of interdomain routing updates. According to the algorithm flow mentioned above, the control information updated for the four main Interzone routes can be defined as IF−J (from the master control server), Isdn (from the control server in the SDN domain), Is−b (from the control server in the BGP-SDN fusion domain), and Ibgp (from the control server in the BGP domain). In the whole network system, a packet transmission task to be completed can be defined as KD(WA → WB), and the master control server can be defined as FKD. If the control server in the information source domain is specified as the master server, it needs to be defined FA ∈ FKD. Based on the above analysis, the algorithm needs to be designated as the master control server, SFsdn is the SDN intra-domain control server, BFbgp is the BGP-SDN intra-domain control server, and the BGP intra-domain control server as FKD. In addition to the function of formulating routing update policies, other intra-domain control servers can implement routing update policies.

To ensure that the entire network system WA → WB. In the control part, the algorithm proposed in this paper emphasizes that on the premise of clearly defining three types of network domains, transmission parameters must be set strictly in the order of “SDN network domain → BGP-SDN fusion domain → BGP network domain”, and the execution of instruction tasks must be completed in order. The transmission parameters of SDN network domain must be set first based on: In the current application of the network system, the processing leading network management status of SDN is network communication mechanism, and BGP network communication mechanism is mainly applied to traditional network system (the mixture, heterogeneous network system is the current network management must face the situation), because the SDN is obviously better than the BGP network management system of network management mechanism, therefore, As long as SDN technology is used in a network domain, it should be used preferentially, and the priority level of pure SDN network domain should be set to the highest.

How do you implement WA → WB The goal of normal network communication to W can be verified by elimination. If the communication between WA and WB cannot be achieved. There must be at least one boundary switch in the whole network. At a certain point in time (or period), it is impossible to ensure smooth communication between the WA → SWsdn → Ws-b → BWbgp → WB network domain sets in sequence. If the boundary switch with possible problems is defined Fe, the reliability of network communication can be finally concluded by finding out the relationship with some key network domain sets and judging whether the inter-domain transmission of packets can be realized. The verification and analysis process is as follows:

  1. (1)

    Fe does not belong to SWsdn Y BWbgp the domain set, which means Fe is not in the network system to which the study belongs. During routing updates, Fe is impossible to receive any data packets, and Fe the possibility of forwarding incorrect data packets does not exist. Even if Fe packets forwarded are irrelevant to this task, inter-domain data packet transmission can be realized WA → WB.

  2. (2)

    Fe belongs to the domain set but does not belong to BWbgp the domain set. Before routing update, Fe is impossible to receive any data packets; When the second step process of the algorithm in this paper is started, Fe the second step process algorithm cannot be directly enabled. However, after adjustment through the feedback mechanism, data packet transmission can be realized. Theoretically, at least, we can know how to realize WA → WB inter-domain data packet transmission.

  3. (3)

    Fe belongs to the SWsdn I BWbgp domain set, which means that the Fe routing update path provided by one of the domain sets is adopted in two stages SWsdn or BWbgp to realize WA → WB inter-domain packet transmission.

  4. (4)

    Fe does not belong to the SWsdn domain set but belongs to the BWbgp domain set. Before routing update, it means that Fe interdomain packet transmission is realized WA → WB through the routing transmission path provided by the domain set in two stages. Before routing update, BWbgp domain set starts the packet transmission path; SWsdn domain collection starts the packet transport path before routing updates.

Through the above assumption Fe and the network state, the relation of four domain sets of packets can be seen from WA → WB an analysis of the network communication results, Fe impossible to interrupt transmission in the network communication between WA → WB domain problems, also proved the reliability of the algorithm in this paper, at the same time, also verified Fe must belong to the above definition of one of the four control server, there is no possibility of a problematic boundary switch.

3 Experiment and Discussion

3.1 Experimental Platform

In the constructed experimental platform, TCP communication protocol (UDP communication protocol can also be used) is the main communication mode between the four types of intra-domain control servers. Some literature points out that the high efficiency of data communication can be guaranteed by using distributed technology [5,6,7]. The virtual network simulation tool Mininet was used to configure the OpenFlow boundary switch [8], and the algorithm in this paper was planted in the master control server and three types of domains. Data packet transmission required in the experiment was completed by network performance testing tool Iperf [9].

3.2 Data Packet Loss Verification

The experiment sends data packets (mainly image files and video files) to the target network domain from the information source through the master control server, and the transmission of data packets is successively through L1–L2–L3–L4–L5–L6–L7 Channel, packets are encapsulated through UDP communication mechanism, and packets are set in two encapsulation modes of 1400 bytes and 20 bytes (at the same time, the purpose of using 20 bytes to encapsulate packets is to provide higher data transmission rate for the experiment). The sending data rate is divided into eight levels and increases successively. The main verification parameters are the number of data packets lost and packet loss rate, and the number of abnormal processing packets and exception processing rate. Main evaluation index parameters, experimental condition parameters and experimental result parameter values are shown in Table 1.

Table 1. Statistical table of simulation results under successively increasing data transmission rates using two packet encapsulation methods.
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3.3 Verifying Interzone Route Update Delay

In the experiment, data packets (with different sizes of transmission files) were sent from the source network domain to the target network domain through the master control server, and the data packets were transmitted through L1–L2–L3–L4–L5–L6–L7 Channel, packets are encapsulated by THE CTP communication mechanism. The average rate of sending data is divided into sixteen levels and increases successively. The main statistical verification parameter is the average transmission rate (SS), transfer file size (DS), routing update times (RS), the normal transmission delay of data packets (TS), route update delay (TF-J), the delay increased by routing update (T△). Main evaluation index parameters, experimental condition parameters and experimental result parameter values are shown in Table 2.

Table 2. Statistical table of simulation results for different incoming files with successively increasing data transmission rates.
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3.4 Discussion of Experimental Results

The data packet loss detection experiment is mainly to verify whether the proposed algorithm can transfer files from the information source to the target network domain under the co-existence of multiple network domains. With the continuous increase of packet transmission rate, all the packet loss rates shown in the experimental results are 0%, which further verifies the correctness of the theoretical analysis mentioned above. Of exception handling the number of packets, is, in fact, this algorithm’s ability to perform routing update test, under the condition of giving a large amount of data transmission, almost under the different data transmission rate, all collected complete exception handling the total number of packets, illustrates the proposed routing update policy has played a role; If the number of exception processing packets is not too large, it indicates that the algorithm in this paper can independently find idle transmission paths, and the design requirements of Interzone route discovery can be realized.

In the experiment of interdomain routing delay detection, the delay length increased by routing update can verify the efficiency of the proposed algorithm. Experimental results show that in the process of packet transmission, the number of route updates is not high and remains relatively stable, indicating that the algorithm is very accurate and fast to find the switch on the idle boundary of the transmission path. Most of the implementation of route updates does not enable the exception handling strategy, which makes the route update delay is not long. In the process of a routing update, the added delay is not long, and with the continuous increase of packet transmission rate, The value increase of T△ is not significant and has little impact on the normal transmission of packets. The results not only further verify the effectiveness of the routing update strategy but also apply to the current constantly developing Internet environment.

In the routing update, the parameters of the data flow table of the boundary switch are mainly set for the part that generates the update, which reduces the space occupation of the internal register in the switch. In the process of data transmission, only the communication delay between the master control server and each network domain server and the communication delay between each network domain server and the corresponding domain boundary switch are defined, which improves the synchronization of multiple processing links in packet transmission. The implementation of the algorithm is mainly accomplished through the master control server, which does not add too many application functions in the SDN module, BGP module, other control servers in the domain and boundary switch, greatly simplifying the subsequent development and application complexity.

4 Conclusion

Based on the definition of network domain and the relationship between domains, this paper takes route discovery and key problem solving as the main breakthrough direction and proposes an algorithm to control routing updates between network domains under the Framework of SDN.

  1. (1)

    In the BGP and SDN converged network domain, the communication protocols are inconsistent, and the control server configuration is relatively independent, which is the main cause of data transmission packet loss and network communication interruption between network domains.

  2. (2)

    Whether in the BGP network domain or the SDN fusion network domain, the configured interdomain routing discovery control server must be based on the SDN network communication rules.

  3. (3)

    In the whole network system, deploy an Interzone routing update master control server, which can effectively prevent the abnormal phenomenon caused by the abnormal processing process of network communication.

  4. (4)

    Define clearly the network domain and set the transmission parameters in the data flow table of the boundary switch according to the correct sequence of a pure SDN network domain, BGP-SDN fusion network domain, and pure BGP network domain, which is the key to realize the non-loss transmission of packets between network domains.

Based on the coexisting simulation experiment platform of the SDN and the BGP-SDN technology, the above conclusions are verified and show that the set between the source domain and target network domain packet transmission path, control of the transmission in the process of data packet loss, the phenomena of routing updates time delay is short, the algorithm has high reliability and feasibility.