E-tickets validation protocols in mobile environment MSS ： verification server maintains a list of E-tickets validated by it. MH ： submit the E-ticket E-ticket validation problem ： validation proce ss The same sequence of an E-ticket should not g et validated more than once . An E-ticket should get validated at least onc e. That is, at least one MSS should accept th is sequence of an E-ticket.
E-tickets validation protocols in mobile environment
Jan 11, 2016
E-tickets validation protocols in mobile environment. MSS ： verification server maintains a list of E-tickets validated by it. MH ： submit the E-ticket E-ticket validation problem ： validation process The same sequence of an E-ticket should not get validated more than once . - PowerPoint PPT Presentation
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E-tickets validation protocols in mobile environment
MSS ： verification server maintains a list of E-tickets validated by it.
MH ： submit the E-ticket
E-ticket validation problem ： validation process The same sequence of an E-ticket should not get validat
ed more than once. An E-ticket should get validated at least once. That is, at
least one MSS should accept this sequence of an E-ticket.
E-tickets validation protocols in mobile environment
E-ticket problem can be defined in short by the following two properties:
(P.1) If a MSS accepts the E-ticket T and it does not crash, then no other MSS accepts T and a MSS does not accept the same E-ticket more than once.
(P.2) Let δ(T) be the set of MSSs that validate the same E-ticket T. If not all MSSs in δ(T) crashes then there is at least one MSS in δ(T) that accepts T.
E-tickets validation protocols in mobile environment
Two Phase E-ticket Validation Protocol (TPEP) Flat scheme algorithm
Tree-Based Protocol (TBP) Hierarchical scheme algorithm
Two Phase E-ticket Validation Protocol
When MH send the E-ticket to the MSS Phase I
The MSS sends an inquiry to all other MSSs in the system visited by the MH, and it validates an E-ticket if none of the responses received from all other MSSs for the same E-ticket is negative.
Phase II It only starts if the MSS gets at least one negative ackno
wledgment. When more than one MSS tries to validate an E-ticket in Phase II, the MSS that is in the same cell as the MH will validate the E-ticket and all others will reject it.
Two Phase E-ticket Validation Protocol
At the end of the protocol, the MSS Si informs the decision on the validation of the E-ticket T to the mobile host, Hi, holding T.
If Hi is disconnected, Si waits for the reconnection of Hi and delivers the message.
Message Type
NEWTKTREQUESTACKACK
POSITIVE NEGATIVE REJECT
ACCEPT
MH 將 E-ticket 傳送給 MSS 做認證MSS 詢問其他 MSSs1. 驗證過此 E-ticket ?2. 其他 MSS 發送相同的 REQUESTACK ?MSS 回覆 REQUESTACK
此 E-ticket 沒有被認證過且沒有其他 MSS 發送過此 E-ticket 的 REQUESTACK給我同時有其他 MSS 正為此 E-ticket 作認證此 E-ticket 我已認證過了MSS 通知所有 MSSs 此 E-ticket 已被我認證了
MSS Si
AllPositive
REJECT
ACK-NEGATIVEACK-POSITIVE
Has RejectHas
Negative
Other MSSs
Alreadyreceived
Otherwise
ACCEPT
ACK-REJECT
Phase I
MH Hi
NEWTKT
REQUESTACK
AlreadyvalidatedACKs
Phase II
Waitreplies
MSS Si
Phase II
More than one MSS tries to validate the same E-ticket T in case the same ticket is submitted for validation by Hi from several places.
MSS Sj
MSS Sk
MH Hi
E-TicketMH Hi
E-Ticket
MH Hi
E-Ticket
cell
cell
cell
Accept
Reject
Reject
Phase II
Phase II
Phase II
Two Phase E-ticket Validation Protocol
Si ： the mobile support station (MSS) Hi ： the mobile host (MH) λS ： the set of MSSs λH ： the set of MHs
δHi： the set of MSSs where Hi visited
visited_ list ( Hi ) → 回傳 Hi 之前拜訪過的 MSS List Search ( Hi ) → 回傳目前正在服務 Hi 的 MSS Nearst ( CurrentMSS , List ) → 回傳 List 中離
CurrentMSS 最近的 MSS
E-ticket’s attribute status : accept or reject ackStatus : positive, negative or reject currentValidator : the set of validators which
are validating this E-ticket
Algorithm to be executed at each MSS Si
Format: (Message Type, ticket, sender, receiver)
Two Phase E-ticket Validation Protocol
存放 REQUESTACK 紀錄 (MSS,T)
傳回結果給 Hi
Hi 之前拜訪過的 MSS 清單
紀錄其他 MSSs 回覆訊息的數量紀錄 Positive ACK 的數量紀錄其他同時認證此 ticket 之 MSSs
PHASE I
此 ticket 是否有其他 MSS 同時在認證 ?
將該 MSS 加入
Otherwise
Alreadyreceived
Alreadyvalidated
Has Reject
從 other MSSs 接收的 ACK 回應
Positive ACKNegative ACK記錄目前正在驗證的 MSS
Otherwise
AllPositive
當 replies >= (RequestACK / 2)
告知所有的 MSS ，此 ticket 已被我驗證過
更新 vTkts , aTkts 資訊
PHASE II
Si 是否為 Hi 目前所在的 MSS 中 ?
NearestAccept
OtherReject
查處 Hi 目前所在的 MSS
Hi 在 Si 範圍且 Hi 未斷線則傳遞
Hi 在 Si 範圍且 Hi 斷線則等 △t 時間後再傳
Hi 不在 Si 範圍則搜尋 Hi 所在的 Si
MSS S1
MSS S2
MSS S3
MSS S4
Correctness of protocol
NewTkt
Req_Ack
Req_Ack
+ACK +ACK
H1 submits T T accepted
H1 submits T
NewTkt
Accept
Accept
Req_Ack
Req_Ack
Req_Ack
-ACK Reject
T rejected
MSS S1
MSS S2
MSS S3
MSS S4
Correctness of protocol
NewTkt
Req_Ack
Req_Ack
H1 submits T
H1 submits T
NewTkt
Req_Ack
-ACK
T rejected
Req_Ack
Req_Ack
+ACK
+ACK -ACK
-ACK
T accepted
Phase II
Analysis of protocol
Three types of messages exchanged in the Phase I of the protocol REQUESTACK ACK ACCEPT
Best Case : MH is residing in only one cell. In this case the number of messages exchanged will be
zero. Worst Case : MH is highly mobile and may cover the
entire network. In this case the number of messages exchanged will be 3(m-1) where m is the number of MSSs.
Avg. Case : The mobile host is limited to a few cells. The number of messages exchanged will be
3(δMH-1) where δMH < m is the number of cells that MH visited.
Tree-based protocol
Hierarchy of geographical region Each node is a MSS Each region is a collection of some MSS’s informati
on and is represented by a internal node. The root node represents the total area spanning o
ver the entire region Each MSS in a higher level of hierarchy knows the i
nformation about E-tickets validated by the lower level nodes
Use the timestamp to choose nearest MSS
Tree-Based Protocol
S1
S7S4
S8 S6 S3 S5S2
Has information ofvalidated ticket
Has information ofvalidated ticket
Has information ofvalidated ticket
Tree-Based Protocol
S1
S7S4
S8 S6 S3 S5S2
NewTkt
Req_Ack
NewTkt
Req_Ack
Already validated
Reject
Tree-Based Protocol
Algorithm to be executed at each MSS Si
Format: (Message Type, ticket, sender, receiver)
將 Request ACK 往 Parent 送
表此 ticket 已被驗證過回傳 Negative ACK
若此 MSS 為 root ，且此 ticket 未被驗證過回傳 Positive ACK
Otherwise將 Request ACK 往上傳
表此 MSS 為驗證的源起者
表此 MSS 非驗證的源起者將 ACK 訊息往下傳
判斷路由 Stack 是否為空
Hi 在 Si 範圍且 Hi 未斷線則傳遞
Hi 在 Si 範圍且 Hi 斷線則等 △t 時間後再傳
Hi 不在 Si 範圍則搜尋 Hi 所在的 Si
S1
S7S4
S8 S6 S3 S5S2
-ACK+ACK
Correctness of protocol
NewTkt
Req_Ack
NewTkt
Req_Ack
If S4 faster than S5
If S4 , S5
At the same time
S5’s timestamp> S4’s timestamp
+ACK-ACK
Analysis of protocol
Two types of messages exchanged in the protocol REQUESTACK ACK
Best Case : The server that gets the ticket and the root being the same, the number of messages is zero.
Worst Case : The server that gets the ticket is at the highest level, the number of
messages will be 2(h - 1) where h is the height of the tree.
Avg. Case : The server that gets the ticket is at a level i, the number of messages will be 2(h – i - 1), where h is the height of the tree.
Comparsion of the protocol
Assumption Without failure The same E-ticket is used once by the users
Comparsion Resilience Latency The number of messages exchanged to validat
e an E-ticket.
Comparsion of the protocol
E-ticket protocol
2PE Internet users
2PE mobile users
Tree protocol
Resilience < n/2 < n/2 < h
Latency 2θ < 2θ << 2θ
Message 2( n - 1) 2(δs - 1) + ( n - 1) 2( h - 1)
Θ : maximum message delayδs : the number of servers visited by the clienth : the height of tree
Request & ACK Request & ACK & Accept
Request & ACK
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