tailieunhanh - Designing and Implementing Linux Firewalls and QoS using netfilter, iproute2, NAT, and filter phần 2

Tham khảo tài liệu 'designing and implementing linux firewalls and qos using netfilter, iproute2, nat, and filter phần 2', công nghệ thông tin, đồ họa - thiết kế - flash phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Chapter 1 Windowing is a process in which the two hosts adapt the number of bytes they send by how many windows the other host receives before sending an ACK packet. For example see the following figure Sender Host Receiving Host send 1 receive 1 send 2 receive 2 send 3 X receive 3 ACK 3 window size 2 send 3 receive 3 send 4 receive 4 send 5 X k receive 5 ACK 5 window size 2 send 5 receive 5 send 6 receive 6 ACK 7 window size 2 The sender host sends three packets before expecting an ACK packet while the receiving host can only process two. The receiving host sends back an ACK packet confirming what packet the sender should send and specifies a window size of 2. The sending host sends packet 3 again but with the same window size 3. The receiver sends ACK 5 meaning that it waits for the fifth packet and specifies again the window size 2. From this point the sender only sends two packets before waiting for an ACK packet from the receiver. Flow control is a mechanism that keeps the data transmission in limits imposed by the physical medium. For example a host on a network that is connected to the Internet through a router with 64 kilobits per second without flow control would flood out 100 megabits per second to the router when sending data to another computer located at the other end of the world. With a flow control mechanism in TCP the hosts negotiate a window size meaning an amount of data to be transmitted by one host at once. ACK packets are sent by the receiving host indicating the last packet has been received and that the receiving host is waiting for the next packet after the one last received. If packets get lost along the way this will force the sending host to resend that packet thus ensuring a reliable communication. 17 Networking Fundamentals Please note that TCP is a connection-oriented protocol with reliable data transmission and flow control. Applications with the need of reliable data transmission use TCP as transport protocol. Examples of such .