路由算法-Tajibnapis提出的变更算法

1、如果在有限次的网络拓扑结构变化后，网络拓扑结构保持为常数，那么算法在有限步后终止。

2、当算法终止时，表Nbu[v]满足：

a)如果v=u，那么Nbu[v]=local;

b)如果从u到v的路径存在，那么，Nbu[v]=w，其中w是从u到v的最短路径上，u的第一个近邻。

c)如果从u到v不存在路径，Nbu[v]=udef

3、算法

var Neighu: set of nodes;(*u的邻居*)

      Du      :arrary of 0...N;(*Du[v] 近似于d(u,v)*)

      Nbu    :array of nodes;(*Nbu[v] is preferred neightbor for v*)

      ndisu  :array of 0....N;(*ndisu[w,v] 近似于d(w,v)*)

Initialization:

      begin forall w∈Neighu,v∈V do ndisu[w,v]:=N;

                forall v∈V do

                          begin Du[v]:=N;Nbu[v]:=udef end;

                Du[u]:=0;Nbu[u]=local;

                forall w∈Neighu do send <mydist,u,0> to w

      end

 

procedure Recompute(v):

     begin if v=u

                 then begin  Du[u]:=0;Nbu[v]:=local end

                 else begin (*估计到v的距离*)

                                  d:=1+min{ndisu[w,v]:w∈Neighu};

                                   if d<N then

                                              begin Du[v]:=d;

                                                       Nbu[v]:=w with 1+ndisu[w,v]=d

                                               end

                                    else begin Du[v]:=N;Nbu[v]:=udef end

                  end;

               if Du[v] has changed then

                      forall x∈Neighu do send <mydist,v,Du[v]> to x

   end

Processing a <mydist,v,d> message from neighbor w:

        {A <mydist,v,d> is at the head of Qwv}

         begin receive <mydist,v,d> from w;

                   ndisu[w,v]:=d;Recompute(v)

          end

Upon failure of channel uw:

        begin receive <fail,w>;neighu:=Neighu\{w};

                   forall vv do Recompute(v)

        end

 

Upon repair of channel uw:

        begin receive <repair,w>;Neighu:=Neighu∪{w};

                  forall v∈V do

                          begin ndisu[w,v]:=N;

                                    send <mydist,v,Du[v]> to w

                          end

          end