tailieunhanh - Network Congestion Control Managing Internet Traffic phần 6

có lý do để hy vọng rằng RED (hoặc một số hình thức khác của hoạt động quản lý hàng đợi) đã được triển khai rộng rãi, và việc sử dụng nó đang phát triển. Trong bất kỳ trường hợp nào, không có đề nghị IETF khác cho hoạt động quản lý hàng đợi đến nay | . TRANSPARENT TCP IMPROVEMENTS 125 The end-to-end argument encompasses an important principle known as fate sharing which is related to the connection-specific state that is stored in the network. Ideally only the communicating endpoints should store the state related to a connection then these peers can only disagree on the state if the path in between them is inoperable in which case the disagreement does not matter. Any additional state stored somewhere in the network should be self-healing that is robust against failure of any entity involved in the communication. Connection splitting is an example of such additional state that may not be self-healing if the sender wrongly assumes that ACKed packets were correctly received by the other endpoint of the connection and the intermediate PEP fails for some reason the packets in its buffer are lost and the connection may end up in an invalid state - the PEP has effectively stolen packets from the connection but it cannot give them back. Another way of saying this would be connection splitting makes the end-to-end connection somewhat less reliable. Breaking the end-to-end semantics of a connection also means that end-to-end security cannot prevail and it does not work with IPSec. Finally connection splitting schemes can have significant processing overhead the efficient maintenance of the intermediate buffer in the face of two asynchronously operating control loops may not be an easy task. For example loop 2a in Figure could fill the buffer in the PEP much faster than loop 2b would be able to drain it - then the sender must be slowed down by some means for example by advertising a smaller receiver window. In the meantime the congestion window of control loop 2b could have grown and all of a sudden the PEP might be required to transfer a large amount of data - it must strike a balance here and the fact that such devices should typically support a large number of flows at the same time while maintaining high .