Measure the Round-Trip Time (RTT) – 作業補充說明Base station (original data server)

Mobile host

RTT (ms)

data size (bytes)

100 200 300 400 500 1000

Number of node:20, 50Overall query rate: 5Simulation time: 100

data size (bytes)100 200 300 400 500 1000

10

20

40

80

10

20

40

80

(a) Node:20 (b) Node:50

1. Scenario_generator2. Node_20.tcl, Node_50.tcl3. AODV directory4. Result: Figure

BS

Mobile Host’s Cache Invalidation

MH

BS

BS use broadcast to invalidate MHs’ cache

MH

Wireless

Broadcast Scalable

MHs MHs wake up and sleep for saving energy Disconnection problem

Cache Invalidation Report (IR), TS (Timestamp) scheme

D. Barbara and T. Imielinski, “Sleepers and Workaholics: Caching Strategies in Mobile Environments,” Proc. ACM SIGMOD Int’l Conf. on Management of Data, Vol. 23, no. 2, pp. 1-12, May 1994.

Invalidation Report (IR) structure

Time

w=i*L

t1t2 t3

t4 t5 t6t7 t8

t9

Broadcastwindow

L

MHs receive IR from BS (1/2)

MHs receive IR from BS (2/2)

Related functions For Base station (server)

/*1.*/ void BS_Database_Update_Model(); /*2.*/ void BS_Broadcast_IR_to_MHs(); /*3.*/ void BS_Recv_data_request_from_MH(Packet *p);

For Mobile host (MHs) /*1.*/ void MHs_Query_Model(); /*2.*/ int MH_Lookup_Local_Cache(int requested_data_id); /*3.*/ void MH_send_data_request_to_BS(int requested_data_id);

/*4.*/ void MHs_Recv_IR_from_BS(Packet *p); /*5.*/ void Remove_invalid_cached_data(int removed_data_id); /*6.*/ void MH_cache_placement(int data_id); /*7.*/ int MH_cache_replacement_LRU();

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aodv_packet.h

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Header embedded

struct hdr_aodv_reply *rh = HDR_AODV_REPLY(p);

rh->my_packet_type = 666; rh->requested_data_id = 132;

666 132

my_packet_type requested_data_id

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Simulation for database AODV.h

struct database { int data_id; float data_size; float nearest_update_time; int flag; //用來模擬資料的狀態，例如存在與否 }; database server_db[1000];

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Simulation for database server_db[1].data_id = 514; server_db[1].data_size = 1024; //bytes server_db[1]. nearest_update_time = 25; //Simulation time server_db[1].flag = 1;

server_db[2].data_id = 587; server_db[2].data_size = 512; //bytes server_db[1].nearest_update_time = 55; //Simulation time server_db[2].flag = 1;

那裡可以設定”變數”的初始值 ? 。 AODV.cc 的建構式函數。

AODV:AODV(……) { ………}

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Update operation for database void AODV::BS_Database_Update_Model() { if (CURRENT_TIME > DATABASE_NEXT_UPDATE) { int update_data_id = rand()%(TOTAL_DATA_SET-1)+1; server_db[1].nearest_update_time = CURRENT_TIME; DATABASE_NEXT_UPDATE = (rand()%

(DATABASE_UPDATE_MEAN*2)+1); } }

void AODV::BS_Broadcast_IR_to_MHs(void) { if (CURRENT_TIME >= NEXT_IR_TIME) { Packet *IR_packet = Packet::alloc(); struct hdr_cmn *ch = HDR_CMN(IR_packet); struct hdr_ip *ih = HDR_IP(IR_packet); struct hdr_aodv_reply *header = HDR_AODV_REPLY(IR_packet);

header->rp_type = AODVTYPE_HELLO; header->Message_type = 1;

int IR_size = 0; float IR_w_interval_time = CURRENT_TIME - (W_WINDOW * IR_INTERVAL);

for(int a=1;a<TOTAL_DATA_SET;a++) { header->Content[a].data_reply_flag = 0; header->Content[a].update_time = 0; if

((BS_database[a].nearest_update_time>IR_w_interval_time)&&(BS_database[a].nearest_update_time>0))

{ header->Content[a].update_time = BS_database[a].nearest_update_time; IR_size += 4*2; } header->Content[a].data_reply_flag = scheduled_data[a]; scheduled_data[a] = 0; }

printf("\nIR_size=%d bytes",IR_size); ch->size() = IP_HDR_LEN + IR_size; ch->ptype() = PT_AODV; ch->iface() = -2; ch->error() = 0; ch->addr_type() = NS_AF_NONE; ch->prev_hop_ = index;

ih->saddr() = index; ih->daddr() = IP_BROADCAST; ih->sport() = RT_PORT; ih->dport() = RT_PORT; ih->ttl_ = 1; Scheduler::instance().schedule(target_, IR_packet, 0.01*

Random::uniform()); } }

Simulation for MHs’ cache #define max_cache_entry 100

struct MH_cache_entry_struct { int data_id; float cached_time; }; MH_cache_entry_struct MH_cache[max_cache_entry];

int AODV::MH_Lookup_Local_Cache(int data_id) { for(int a=0;a<max_cache_entry;a++) { if (MH_cache[a].data_id==data_id) { return 1; } } return 0; }

int AODV::MH_cache_replacement_LRU() { int compared_time = 99999; int replace_location = 0;

for(int a=0;a<max_cache_entry;a++) { if (MH_cache[a].cached_time < compared_time) { compared_time = MH_cache[a].cached_time; replace_location = a; } } return replace_location; }

void AODV::MH_cache_placement(int data_id) { int place_location = 0; place_location = MH_cache_replacement_LRU(); MH_cache[place_location].data_id = data_id; MH_cache[place_location].cached_time = CURRENT_TIME; }

void AODV::MHs_Recv_IR_from_BS(Packet *IR_packet) { struct hdr_aodv_reply *header = HDR_AODV_REPLY(IR_packet); //Use IR to remove the invalid cached data in MH for(int a=0;a<max_cache_entry;a++) { int data_id = MH_cache[a].data_id; if (MH_cache[a].cached_time < header->Content[data_id].update_time) { Remove_invalid_cached_data(data_id); } }

if (MH_status == 3) //Cache hit, IR invalid, and then receive data reply { MH_cache_placement(queried_data_id); MH_status = 0; queried_data_id = 0; query_time = 0; }

if (MH_status == 1) //Cache hit, waiting IR { if (MH_cache[queried_data_id].cached_time >= header->

Content[queried_data_id].update_time) { MH_status = 0; queried_data_id = 0; query_time = 0; } if (MH_cache[queried_data_id].cached_time < header-

>Content[queried_data_id].update_time) { MH_status = 3; Remove_invalid_cached_data(queried_data_id); MH_send_data_request_to_BS(queried_data_id); } }

if (MH_status == 2) //Cache miss, wait and receive data reply { MH_cache_placement(queried_data_id,data_Q_bit,data_U_bit); MH_status = 0; queried_data_id = 0; query_time = 0; } Packet::free(IR_packet); }

Updated Invalidation Report (UIR) scheme

G. Cao, “A Scalable Low-Latency Cache Invalidation Strategy for Mobile Environments,” IEEE Trans. on Knowledge and Data Engineering, Vol. 15, No. 5, pp. 1251-1265, Sept./Oct. 2003.

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期中 NS-2 Project Use NS2 to implement UIR (Updated Invalidation Report) scheme

Reference G. Cao, “A Scalable Low-Latency Cache Invalidation Strategy

for Mobile Environments,” IEEE Trans. on Knowledge and Data Solve Problem: Cache Consistency Problem