IP分片重组中的数据重叠是如何产生的？分片的时候应该是不存在重叠的，为什么到了接收端可能存在重叠呢？求指点

[wang_yue]

如题，没想明白为什么IP包的分片重组为什么会存在数据重叠！

[UDX协议]

Packet Duplication If packets can be lost in the network, can they be duplicated? Perhaps surprisingly, the answer is yes! It is possible for a source to send a single packet, yet for the receiver to get multiple copies of that packet. The most likely reason for duplication is faults in routing/switching elements within the network; duplication should not happen in normal operation. How common is duplication? Paxson's measurements revealing the tendency of back-to-back packet losses also showed a small amount of packet duplication. In measuring 20,000 flows, he found 66 duplicate packets, but he also noted, "We have observed traces . . . in which more than 10% of the packets were replicated. The problem was traced to an improperly configured bridging device."HTPU95UTPH A trace that I took in August 1999 shows 131 duplicates from approximately 1.25 million packets. Packet duplication should not cause problems, as long as applications are aware of the issue and discard duplicates (RTP contains a sequence number for this purpose). Frequent packet duplication wastes bandwidth and is a sign that the network contains badly configured or faulty equipment.