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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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Most of the UNI abstract messages are directly supported by re-using existing procedures, messages, and objects defined in RSVP-TE and GMPLS extensions of RSVP-TE. Table 9.1 gives the mapping between the OIF UNI abstract messages and the RSVP messages.
Connection establishment
To create a connection, the source UNI-C sends a Path message to its source UNI-N. The Path message includes a GENERALIZED LABEL REQUEST object which indicates that a label binding is requested for this connection. The traffic parameters of the connection are encoded in a SONET/SDH SENDER TSPEC object in the Path message and a SONET/SDH FLOWSPEC object in the corresponding Resv message. Figure 9.33 shows the message flow during a successful connection establishment. It is assumed that the source UNI-N sends a Resv message to the source UNI-C after the segment of the connection within the optical network has been established.
To request a bidirectional connection, a UNI-C must insert an UPSTREAM LABEL object in the Path message to select the upstream label(s) for the connection.
Connection deletion
A connection in RSVP can be deleted by either using a single PathTear message or an ResvTear and PathTear message combination. Upon receipt of the PathTear message, a
Table 9.1 Mapping between abstract messages and RSVP messages.
Abstract message RSVP message
Connection create request Path
Connection create response Path, PathErr
Connection create confirmation ResvConf
Connection delete request Path or Resv
Connection delete response PathErr, PathTear
Connection status enquiry implicit
Connection status response implicit
Notification PathErr, ResvErr
PROBLEMS
235
Source Source Destination Destination
UNI-C UNI-C UNI-N UNI-C
Figure 9.33 Successful connection establishment using RSVP.
node deletes the connection state and forwards the message. In optical networks, however, the deletion of a connection in a node can cause the downstream nodes to think that the connection has failed, which can then lead to network management alarms and perhaps the triggering of a restoration/protection mechanism for the connection. In view of this, a graceful connection deletion mechanism is proposed in the GMPLS extensions for RSVP-TE. Under this procedure, a Path or Resv message with the “deletion in progress” bit in the ADMIN_STATUS object set, is sent along the connection’s path to inform all nodes en route of the intended deletion.
PROBLEMS
1. Explain in your own words why traffic cannot be dropped or added to a lightpath at intermediate OXCs.
2. Consider the optical network shown in Figure 9.4. SONET/SDH framing is used on each fiber link with a transmission rate of OC-48/STM-16 (2.488 Gbps). The subrate unit is an OC-3/STM-1 (155 Mbps). Assuming that none of the OXCs are equipped with a SONET/SDH DCS, identify the set of lightpaths that will satisfy the demand, expressed in subrate units, given in the table below.
OXC 1 OXC 2 OXC 3 OXC 4 OXC 5 OXC 6
OXC 1 _ 5 8 10 12 16
OXC 2 - - 5 1 12 16
OXC 3 - - - 5 10 -
3. In the above problem, assume that OXCs 3 and 5 are equipped with a SONET/SDH DCS.
a. Identify any set of lightpaths that will satisfy the demand given in the table, which requires fewer lightpaths than the set identified in Problem 3.
b. How many wavelengths are required on each fiber to carry these lightpaths?
4. Consider the unidirectional path sharing ring (OUPSR) described in Section 9.2.2. What is the available capacity of the ring for the transmission of working traffic?
236
WAVELENGTH ROUTING OPTICAL NETWORKS
5. Identify all of the lightpaths that are SRLG-disjoint to the lightpath {2, 7, 12} in the optical network shown in Figure 9.7.
6. Explain what is a control plane and what is a data plane?
7. In GMPLS, what is the difference between a suggested label and a label set? Give an example where the label set can be used.
8. What are the differences between GMPLS and the OIF UNI?
APPENDIX: SIMULATION PROJECT: CALCULATION OF CALL BLOCKING PROBABILITIES IN A WAVELENGTH ROUTING NETWORK
The objective of this simulation project is to calculate the blocking probability of dynamically arriving call requests for the establishment of lightpaths in a network of OXCs. Each OXC might have no converters, partial conversion, or full conversion.
Project Description
You will simulate five OXCs, arranged in series and numbered from one to five. OXC i and i + 1, i = 1, 2, 3,4, are linked by a single fiber that carries W wavelengths. The value of W will be specified as input to the simulation. You will only simulate calls in one direction. That is, calls arrive at each OXC i and their destination is always an OXC j, where j > i.
Calls originating at OXC 1 can require a 1-hop, 2-hop, 3-hop or 4-hop path. A 1-hop path is a path from OXC 1 to OXC 2. That is, it originates at OXC 1, uses the link between OXC 1 and 2, and terminates at OXC 2. A 2-hop call uses the link between OXCs 1 and 2, and 2 and 3, and terminates at OXC 3. The same goes for the 3-hop and 4-hop calls. A call originating at OXC 2 can be a 1-hop, 2-hop, or 3-hop call. A 1-hop call uses the link between OXC 2 and 3 and terminates at OXC 3. A 2-hop call uses the link between OXCs 2 and 3 and OXCs 3 and 4, and terminates at OXC 4. Finally, a 3-hop call uses the links between OXCs 2 and 3, OXCs 3 and 4, and OXCs 4 and 5, and terminates at OXC 5. Similarly, for OXC 3, we can have 1-hop and 2-hop calls to OXC 4 and 5, respectively; and for OXC 4, a 1-hop call to OXC 5.
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