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Connection Oriented Networks - Perros H.G

Perros H.G Connection Oriented Networks - John Wiley & Sons, 2005. - 359 p.
ISBN 0-470-02163-2
Download (direct link): connectionorientednetworks2005.pdf
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An example of how a connection over the UNI between two peer signaling protocols is terminated is shown in Figure 5.6. The signaling protocol issues an AAL-RELEASE.request to SAAL, in response of which the SSCOP sends an END frame to its peer SSCOP. The peer SAAL sends an AAL-RELEASE.indication to the peer signaling protocol, and its SSCOP returns an END ACKNOWLEDGE frame, upon receipt of which the SAAL issues a AAL-RELEASE.confirm to the signaling protocol.
An example of how a signaling protocol transfers messages to its peer protocol is shown in Figure 5.7. The signaling protocol transfers a message to SAAL in an AAL-DATA.request, which is then transferred by SSCOP in an SD frame. The SD frame is passed onto AAL 5, which encapsulates it and then breaks it up to 48 byte segments, each of which is transferred by an ATM cell. Figure 5.7 also shows the POLL/STAT frames exchanged between the two peer SSCOPs. The SD frame at the destination side is delivered to the peer signaling protocol using the AAL-DATA.indication primitive.
SAAL
SAP
SSCOP
SSCOP
SAAL
SAP
AAL-REL.
request
AAL-REL.
confirm
Figure 5.6 Termination of a connection between two peer signaling protocols.
ATM ADDRESSING
123
SAAL
SAP
SSCOP
SSCOP
SAAL
SAP
AAL-DATA.
request
AAL-DATA.
indication
Figure 5.7 Transfer of a signaling message.
5.4 THE SIGNALING CHANNEL
This is a VC connection that is used exclusively to carry the ATM traffic that results from the exchange of signaling messages between two peer signaling protocols. It is a default connection identified by VPI = 0 and VCI = 5. This signaling channel is used to control VC connections within all of the virtual paths. It is also possible to set up a signaling channel with a VCI = 0 within a virtual path connection with a VPI other than 0, say with a VPI = x .In this case, this signaling channel can only be used to control VC connections within the virtual path x.
The signaling channel VPI/VCI = 0/5 is used in conjunction with the signaling mode known as non-associated signaling. In this mode, all of the VC connections are created, controlled, and released via the signaling channel VPI/VCI = 0/5. A signaling channel within a VPI = x, where x > 0, is used in conjunction with the signaling mode known as associated signaling. In this mode, only the VC connections within the virtual path x are created, controlled, and released via the signaling channel VPI/VCI = x/5.
5.5 ATM ADDRESSING
Each ATM end device and each ATM switch has a unique ATM address. Private and public networks use different ATM addressing formats. Public ATM networks use E.164 addresses, whereas ATM private network addresses use the OSI network service access point (NSAP) format.
The E.164 addressing scheme is based on the global ISDN numbering plan (see Figure 5.8). It consists of sixteen digits, each of which are coded in binary coded decimal (BCD) using 4 bits. Thus, the total length of the E.164 address is 64 bits (or 8 bytes). The first digit indicates whether the address is a unicast or multicast. The next three digits indicate the country code, and the remaining digits are used to indicate an area or city
digits 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
U,
M
Country
code
Area, city, exchange, end-system
Figure 5.8 The E.164 addressing scheme.
124
SIGNALING IN ATM NETWORKS
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
AFI DCC High-order DSP (HO-DSP) ESI SEL
IDP---> DSP
DCC ATM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
AFI ICD High-order DSP (HO-DSP) ESI SEL
IDP---> ---* DSP
ICD ATM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
AFI E.164 HO-DSP ESI SEL
----------------- IDP------------------------------------------------- DSP ----------------------------^
\---------------- IDI------------------>
E.164 ATM
Figure 5.9 The NSAP ATM formats.
code, an exchange code, and an end device identifier. When connecting a private ATM network to a public network, only the UNIs connected directly to the public network have an E.164 address.
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