(3) Stream Sequence Number = n (2) Stream ID = S
Type = 0 Reserved UBE
U: Unordered bit
B: Beginning fragment bit E: Ending fragment bit
Figure 1.2.3: DATA Chunk Format
The lifetime of an SCTP association consists of three phases [14]: association establishment, data transfer, and association termination. SCTP uses a four-way handshake and cookie mechanism to establish an association that prevents blind SYN attacks (to be elaborated in Section 4.2). After the association is established the two
SCTP endpoints can trans e elaborated in Section
4.3). The association termination can be initiated by either one of the endpoints engaged
data
t aling links. The GPRS core etwork consists of GPRS Support Nodes (GSNs) such as Serving GPRS Support Node
y GPRS Support Node (GGSN; see Fig. 1.3.1 (d)).
, fer data by using the DATA chunk (to b
in the association and is a three-way handshake process.
1.3 GPRS Network Signaling
General Packet Radio Service (GPRS) [1] supports high-speed Packet Switched (PS) for accessing versatile multimedia services anytime and anywhere. Figure 1.3.1 shows the architecture for the GPRS PS service domain. In this figure, the dashed lines represen signaling links, and the solid lines represent data and sign
n
(SGSN; see Fig. 1.3.1 (c)) and Gatewa
PDN
Radio Network SGSN GGSN
HLR
GGSN: Gateway GPRS Support Node HLR: Home Location Register
MS: Mobile Station
PDN: Packet Data Network
SGSN: Serving GPRS Support Node Core Network
Figure 1.3.1: GPRS Network Architecture
An SGSN connecting to the Radio Network (see Fig. 1.3.1 (a)) plays a role in the PS service domain similar to a mobile switching center in the circuit switched service domain (i.e., the GSM core network). The GGSN interworks to the external Packet Data Network (PDN; see Fig. 1.3.1 (e)). The Hom
the master database containing all user-related subscriptions and location information.
de tities addresses these SEs with subsystem numbers. The subsystem numbers for GSM MAP ASEs are listed
e Location Register (HLR; see Fig. 1.3.1 (b)) is
For mobility management and session management [3], the HLR communicates with both SGSN and GGSN through the Gr and Gc interfaces, respectively. These two interfaces are based on the GSM Mobile Application Part (MAP) [2].
As shown in Figure 1.3.2 (a), GSM MAP is an application of the SS7 protocol described in Section 1.1. GSM MAP uses SCCP classes 0 and 1 connectionless services to provi efficient routing with or without maintaining message sequencing. The network en may consist of several application service elements (ASEs). The SCCP
A
in [11]. For intra-GSM network message delivery, the destination address of the message
may be a simple destination point code (DPC) that can be used by the MTP for direct routing. For inter-GSM network message delivery, the originating node does not have enough knowledge to identify the actual address of the destination. In this case, the SCC translates the actual destination address by Global Title Translation (GTT) [7]. Then, the SCCP layer invokes the MTP_TRANSFER primitive to provide the MTP layer message transfer services. The MTP layer generates the SS7 MTP message, and the message is sent to the destination over MTP-based SS7 network. The above descriptions assume th MTP-based protocol layers. These protocol layers can be replaced by the SCTP-based protocol hierarchy as shown in Figure 1.3.2 (b). When the SCCP layer invokes
MTP_TRANSFER primitive to the M3UA layer, the M3UA layer generates the appropriate M3UA packet. Then the packet is sent to the destination through the SCTP/IP/Ethernet layers.
P
e
(a) MTP-based GSM MAP (b) SCTP-based GSM MAP
MTP3 User Adaptation Layer (M3UA) Stream Control Transmission Protocol
(SCTP)
Ethernet Message Transfer Part Level 3 (MTP3)
Message Transfer Part Level 2 (MTP2)
Message Transfer Part Level 1 (MTP1) Physical
Data Link Network
Mobile Application Part (MAP)
Transaction Capabilities Application Part (TCAP)
Signaling Connection Control Part (SCCP) Mobile Application Part (MAP)
Transaction Capabilities Application Part (TCAP)
Signaling Connection Control Part (SCCP) Presentation
Figure 1.3.2: GSM MAP Protocol Hierarchy
The GPRS network entities (such as SGSN and HLR) communicate with each other through MAP dialogues by invoking MAP service primitives. A service primitive can be one of four types: Request, Indication, Response, and Confirm. The service primitive is initiated by a MAP service user of a network entity called the dialogue initiator, as shown in Figure 1.3.3 (1). The service type is Request. This service request is sent to the MAP service provider of the network entity.
imitive with type Indication to inform the destination MAP service user (see Figure 1.3.3 (2)). In most cases, the information (parameters) of the service with type Indication is identical to that with type Request. The primitive is typically a query, which asks the dialogue responder to perform some
operations.
A corresponding service acknowledgment, with or without results, may be sent from the dialogue responder to the dialogue initiator. The same service primitive with type
Figure 1.3.3: GSM MAP Service Model
The service provider delivers the request to the peer network entity (i.e., the dialogue responder) by TCAP. When the MAP service provider of the peer network entity receives the request, it invokes the same service pr
Service_ack (Confirm)
Dialogue Initiator Dialogue Responder
MAP Service User MAP Service User
Service (Request)
Service (Indication) Service_ack (Response)
1 4 3 2
MAP Service Provider MAP Service Provider
Response is invoked by the MAP service user of the dialogue responder (see Figure 1.3.3 (3)). After the MAP service provider of the dialogue initiator receives this response, it invokes the sam itive with type Confirm (see Figure 1.3.3 (4)). The
and the Response se most cases, except that the Confirm service m vider error parameter to indicate a protocol error.
A MAP dialogue consists of several MAP services to perform a common task. The
services are either speci e:
Mobility services
l s defined in GSM MAP [2], six common MAP services are described as llows:
n types,
col to the peer entities. This service does not have any parameters and is not
e service prim
parameters of the Confirm rvices are identical in ay include an extra pro
fic or common. The specific services includ
Operation and maintenance services Call-handling services
Supplementary services
Short message service management services
The common MAP services are used to establish and clear MAP dialogue between peer MAP service users. They invoke functions supported by TCAP and report abnorma situations. A
fo
MAP_OPEN is used to establish a MAP dialogue. This service is confirmed by the service provider; That is, MAP_OPEN has the Request/Indication and Response/Confirm types.
MAP_CLOSE is used to clear a MAP dialogue. This service is not confirmed by the service provider; that is, the service primitive only has the Request/Indicatio but not the Response/Confirm types.
MAP_DELIMITER is used to explicitly request the TCAP to transfer the MAP proto data units
confirmed by the service provider.
E
ing for mobile networks is implemented in MTP-based SS7 Telecommunication System (UMTS) all-IP architecture
ied out by IP-based SS7 network.
In ely, based approach and the SCTP-based approach. Chapter 2 describes our
s in
three ck. We
also i f the SCTP-based and the MTP-based MAP approaches
Speci
For the descriptions of the MAP_U_ABORT, MAP_P_ABORT, and MAP_NOTIC services, the readers are referred to [2,3].
1.4 Motivation
Traditionally, the SS7 signal network. In Universal Mobile
[18,19,20], the SS7 signaling transport will be carr
Evolving from GSM and GPRS, the UMTS all-IP architecture integrates the IP and mobile technologies. Such integration results in lower cost of IP-based SS7 network.
this thesis, we implement and discuss two approaches for SS7 signaling transport; nam the
MTP-implementations of theses two approaches. Chapter 3 compares these two approache perspectives: message format, connection setup, and data transmission/A
llustrate the performance o
by using the Send Authentication Info procedure defined in 3GPP Technical fication 23.060 [1] as an example. Finally, Chapter 4 concludes our research.