Currently, most businesses provide services online. The availability of online services is the first. These are usually provided through two or more different Internet service provider (ISP) lines. However, the problem is that how can the external users balance the load across these two ISP lines? The traditional method is to use DNS load balancing from the ISP where the domain name was issued. Nevertheless, DNS load balancing cannot provide health-checking of the stability of the lines, the web server’s public IP address returned to the client depends on the record registered on the ISP’s DNS server.
1. Description of traditional connection
When a customer emails to a client at the address xxx@company.com.vn in your company, such email will be sent as follows:
1. Client will send a DNS caching query to check the email xxx@company.com.vn belongs to the server with which public IP address.
2. If the DNS caching already has a record for mail.company.com.vn, DNS will return the IP address to the client. If the DNS caching has no information about this domain, DNS caching will contact the DNS root server requesting “record” of the Primary and secondary IP addresses of this domain.
3. Root Name Server is one of 13 root name servers servicing the Internet. These servers contain DNS server information including record of domain company.com.vn, Root Name server returns DNS caching server the IP addresses of these servers (The DNS Authority- A DNS).
4. DNS Caching sends query to A-DNS to get records of mail.company.com.vn.
5. A-DNS (DNS Authority) returns record of mail.company.com.vn including IP addresses and TTL values. A sequence number allows DNS caching to determine whether the record has changed since the last update.
6. DNS caching server sends IP addresses of mail.company.com.vn to the user (client).
7.Client establishes connection to mail.company.com.vn.
8. Client sends email to the Mail server mail.company.com.vn.
9.Mail server then forwards email to the user xxx@company.com.vn.
2. Description of Ecessa load balancer
With this solution, MX Record of the domain company.com.vn will be declared on Ecessa. (This must be registered with VNNIC – Vietnam Internet Network Information Center). When a customer emails to a client at xxx@company.com.vn in your Company, these steps will be followed:
1. Client will send a DNS caching query to check the email xxx@company.com.vn belongs to the server with which public IP address.
2. If the DNS caching already has a record for mail.company.com.vn, DNS will return the IP address to the client. If the DNS caching has no information about this domain, DNS caching will contact the DNS root server requesting “record” of the Primary and secondary IP addresses of this domain.
3. Root Name Server is one of 13 root name servers servicing the Internet. These servers contain DNS server information including record of domain company.com.vn, Root Name server returns DNS caching server the IP addresses of these servers (The DNS Authority- A DNS).
4.DNS caching server sends mail record request to Ecessa over one of two WAN lines (if WAN line 1 is down, DNS caching server will send query to Ecessa over WAN line 2).
5. A-DNS (Ecessa) returns the record for the DNS caching server. This record contains two IP addresses of mail.company.com.vn, time-to-live (TTL), and a sequence number that allows the DNS caching server to determine whether the record has changed since the last update. The assigned TTL is small enough to ensure that the DNS caching server returns correct information to the client even when there is a problem on the WAN line 1 or WAN line 2. The Ecessa device monitors the WAN Link lines, if a problem is detected on any line, the device automatically removes the IP address from the mail record, changes the sequence number, and instantly updates the DNS caching servers. If the lines are stable, the DNS caching server does not need to update the full record, minimizing bandwidth due to updating TTL information.
6. DNS caching server sends one of the WAN IP addresses representing mail.company.com.vn to the client, the IP addresses of these WAN lines will be sent sequentially to the queries of different clients (Load balancing).
7. Client can send email to the mail server over different WAN lines without return.
Contact Us:DL IT INVESTMENT CORPORATION
- Address: 152/32 Thanh Thai, Ward 12, District 10, HCMC
- Telephone: (84-28) 62650735 - Fax: (84-28) 62650734