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Grid networks enabling grids with advanced communication technology phần 9

Tình trạng này tạo ra một lỗ hổng cho một số loại tấn công nguy hiểm. Như một vấn đề của thực tế phổ biến, một sự kiện rekeying nên xảy ra bất kỳ thời gian byte B đã được gửi thông qua một hiệp hội bảo mật mã hóa mà mật mã chuyển đổi sử dụng một chế độ CBC hoạt động (ví dụ, 3DES) [21]. Sự kiện này đặt B n / 8 * 2 n / 2, trong đó n là kích thước khối bit. | 270 Chapter 13 Network Monitoring Restoration Routing Decision Node RDN is assumed. The first three schemes basic standalone mechanisms and the last scheme attempts to find the best combination of the above two schemes. The primary route from node I to E is depicted as a thick black line and the link 2 3 is assumed to be broken during the operation. 13.6.2.1 Global routing update When the headend 2 or tailend 3 of link 2 3 detects the link failure it informs the RDN via the control plane. The RDN conducts the routing recomputation and updates the forwarding tables for all nodes and new bursts will subsequently follow the new routes. For example new bursts will follow the route I 4 5 6E. This solution is optimal and the existing routing protocol can handle it well. However global routing table updating is a slow process in seconds or even minutes due to the long round-trip time for the signal transmission and processing between the OBS nodes and the routing entity. As a result a large amount of bursts will be lost before the forwarding tables are updated. 13.6.2.2 Local deflection This is similar to the traditional deflection routing usually seen in a congestion resolution scheme. When the headend 2 detects the link failure it will automatically pick up the alternative next hop in the forwarding table for every new burst whose next hop on its primary route passes the faulty link. In the example new bursts from I to E will follow the alternative route I 1 2 5 6 E. This would be the fastest restoration scheme since new bursts will be deflected to an alternative good link right after the link failure is detected locally. Therefore it will incur the smallest restoration loss. However because all the affected bursts are deflected to one alternative path this scheme would increase the congestion loss. 13.6.2.3 Neighbor deflection In this scheme the headend 2 will also send a different fault notification message to all its adjacent nodes in addition to the one to the RDN.