Bonded Broadband Implementation
The Bonded Broadband service is implemented using load balanced gre tunnels between our Tunnel server and the Client router. An Internet IP address subnet is routed through the tunnels to the Client router. It is this subnet which the Client will use for all incoming and outgoing traffic.
The Client router will establish a GRE tunnel via each of its broadband connections to the tunnel server. Each connection is tested every 5 seconds to ensure the connection is up. Once the tunnel is up, the connection is added to the load balancer logical device (TEQL on Linux). The load balancer device will send packets outgoing through the available tunnels on a round robin basis.
If a connection ceases to respond, then the tunnel is removed from the load balancer, and packets will then only be sent out through the remaining connections. The tunnel will be automatically added back to the load balancer with connection is re-established.
The Tunnel server performs the same process in reverse. A tunnel is established to each public IP address on the Client router. Tunnels are added to, or removed from the load balancer when the connection goes up or down.
Tunnel Overhead
The gre tunnel overhead is 28 bytes per packet. Assuming an average packet size of around 1000 bytes, then the tunneling overhead will be roughly 3%. Applications that regulary use smaller packets will incur a heavier overhead for example an packet size of 128 bytes will have an overhead of around 20%. In most cases we expect the bonded service to achieve about 95% of the theoretical maximum.
Packet Sequencing
The service does not guarantee that all packets will arrive in the original order. This may cause some intermittant problems on certain services. There are options to set up both the Tunnel server and the Client router to send certain types of packets via a single channel only, thus ensuring correct ordering. Investigation and configuration of the Tunnel server and Client router may involve consultancy charges.
If you intend to bond services from two or more different suppliers you must ensure that the services have similar capacity (speed and contention) and round trip delay (ping time) otherwise you may experience problems due to packets arriving out or sequence.
Quality of Service
Options are available to prioritise packets for services requiring minimum delay. Prioritisation can be performed on packet size, protocol and ports number or by source or target IP address. For example, QOS settings can be made reduce the impact of heavy downloads on your Voice over IP traffic.
Alerts
The customer has the option of receiving an email alert from both the Tunnel server and the Client router. Alerts can be generated when a connection goes up or down, or when there are no remaining connections to send tunneled packets.
Security
There is currently no encryption on the data transmitted through the tunnel. There is no major difficulty in establishing IpSec secure tunnels, however the service is designed to carry ordinary Internet traffic and there is no advantage to be gained in encrypting packets from the Client which will be promptly de-crypted on the tunnel server and despatched over the Internet.
The service does not preclude any ipv4 encryption such as IPSec being performed to establish VPN connections from Client to Client or to other Internet locations. |
