TCP with Buffering Capability and Sequencing Information

TCP with Buffering Capability and Sequencing Information that is TCP-BUS is related to the TCP-F and TCP-ELFN. As the name says, it has both buffering capabilities and can sequence information.

It is used to improve the performance of TCP in the ad-hoc wireless network. The operation is highly dependent on Associativity Based Routing(ABR). In TCP-BUS messages that are transmitted can be divided into two different types:

• TCP Connection
• Segment Information:  It can be further divided into two segments of messages:
  •  LQ: LQ message carries the segment sequence number at the head of the queue at the pivot node.
  • REPLY:  REPLY carries the sequence number of the last successful segment at the receiver. 

TCP-BUS uses Explicit Route Disconnection Notification(ERDN) message to send the message about the path break message. If the path is re-established, it uses the ERSN message, Explicit Route Successful Notification. 

There are five nodes in the diagram and each node is connected to some other node. Here a is the source or sender and c is the destination or receiver. When a path break occurs between nodes b and c, the node that detects the path break is called the pivot node. Here b is the pivot node. Upon detecting a path break, the b node buffers the packets. The pivot node will now send an ERDN message to the sender a. Upon receiving the ERDN message, the source freezes and stop transmitting any more packets. Now the pivot node b will send a route notification packet to all other downstream nodes called the route notification packet to find an alternate route to the destination. Now after finding an alternate route to destination c, the new found route will be sent to the source node a by pivot node b as an ERSN message. After this, node a needs to know which packets are buffered by node b so that information is exchanged between node b and node a via LQ and REPLY messages denoted via a non-continuous arrow in the picture.   

Advantages

• Improved performance.
• Buffering, sequence numbering, and selective acknowledgment reduce the chances of faults or sending packets with errors or packets not reaching the destination at all.

Disadvantages

• Increased reliance on the routing protocol and the buffering at the intermediate nodes. The failure of intermediate nodes that buffer the packets may lead to packet loss and performance degradation.
• The reliance on the routing protocol may lead to performance limitations with other routing protocols that do not boast similar advantages of control messages as in Associativity Based Routing.