Survivability in the Optical Internet Using the Optical

Survivability in the Optical Internet Using the Optical Burst Switch Seunghun Oh, Younghan Kim, Myungsik Yoo, and Hyun Ha Hong ETRI Journal, Volume 24, Number 2, April 2002 Presented by - Ashish Deshmukh 03/02/05 CEG 790 1

Overview n n n Introduction to optical switching Restoration and protection in optical networks MPLS restoration Overview of OBS Restoration in OBS q Temporary LSP q Bossy LSP Simulation results 03/02/05 CEG 790 2

Optical Switching Techniques n n n Optical circuit switch (OCS) q Dedicated circuit between two end points Optical packet switch (OPS) q Routing information within the packet Optical burst switch (OBS) q Better utilization by statistically multiplexing data bursts q No need of optical random access memory q Provides a better way of improving OCS while attenuating problems with OPS 03/02/05 CEG 790 3

Survivability n Survivability important q q 03/02/05 Huge amount of data traffic carried by single fiber A fault brings multiple session errors in a higher layer So many restorations required This is heavy burden on the network CEG 790 4

Current optical internet architecture and problems n IP/ATM/SONET/WDM q Unnecessary overlapped functions n n 03/02/05 The layers are independent from each other So it is slow and not able to scale for large volume of traffic CEG 790 5

Future optical internet architecture n IP/WDM q q 03/02/05 More scalable OBS technology can better support the architecture because of it advantages over OCS and OPS CEG 790 6

Focus of this paper n n n OBS specific restoration The concept of Multi-protocol Labeled Switch (MPLS) restoration scheme is used for OBS restoration This paper demonstrate that the features of the OBS can efficiently enhance the survivability of the optical Internet by increasing the possibility of fault localization 03/02/05 CEG 790 7

Restoration n Protection Dynamic recovery Depending on location q n Local or global restoration Protection q q 03/02/05 Dedicated Shared CEG 790 8

Protection n A backup path is calculated along with the working path Network fault will be restored with this preplanned path Disadvantages q q 03/02/05 Difficult to restore multiple failures Difficult to restore node failure CEG 790 9

Dynamic Recovery n n Backup path is calculated and established after detecting network fault Advantages q q n Better network utilization Able to restore node failure, multiple network failure Disadvantage q 03/02/05 Long restoration time CEG 790 10

Restoration n Restoration in optical networks MPLS restoration Restoration in OBS 03/02/05 CEG 790 11

Restoration in optical network (WDM) n n Restoration consists of two sub-layers: Optical channel restoration q n Path restoration scheme Optical multiplex restoration q 03/02/05 Link restoration scheme CEG 790 12

Restoration in optical network continued. . n n n Dynamic optical recovery schemes Optical protection schemes Restoration schemes specific to Network Topology 03/02/05 CEG 790 13

Dynamic optical recovery scheme n n Backup path is dynamically calculated This can be done in either centralized or distributed way q 03/02/05 It is the node at the link failure that executes restoration, so it is better to calculated path dynamically in a distributed way[17]. CEG 790 14

Optical protection schemes n n Dedicated protection (1+1) Shared protection (1: N) Dedicated protection (1+1) 03/02/05 CEG 790 15

Network specific restoration schemes n n Protection in point-to-point network Ring based restoration q Self healing ring n n Unidirectional path switched ring, SPRING/2, SPRING/4 Restoration in Mesh network 03/02/05 CEG 790 16

Restoration n Restoration in optical networks MPLS restoration Restoration in OBS 03/02/05 CEG 790 17

MPLS Restorations n Fault detection q n Fault notification q n n n Fault detecting LSR notifies path switch LSR (PSL) Restoration switching q n Using a link probing mechanism between neighboring LSR PSL switches traffic from working path to backup path LSR: Label switching router PSL: Path switch LSR PML: Path Merger LSR RNT: Reverse notification tree FIS: Fault indication message 03/02/05 CEG 790 18

MPLS Restorations 03/02/05 CEG 790 19

MPLS Restorations 03/02/05 CEG 790 20

Classification of MPLS Restoration 03/02/05 CEG 790 21

Restoration n Restoration in optical networks MPLS restoration Restoration in OBS 03/02/05 CEG 790 22

Restoration based on OBS n n n Overview of OBS Network Failures and Detection Restoration procedure in the OBS q q 03/02/05 Link level restoration Path level restoration Temporary LSR Bossy LSR CEG 790 23

Overview of OBS n OBS has to network with non-OBS domains, the edge router in OBS should take care of this. 03/02/05 CEG 790 24

Concept of OBS n n n Edge routers assembles packets into a proper size data burst according to network management policy and first sends the BCP followed by data burst With JET, O/E/O is not required Another feature is delayed reservation 03/02/05 CEG 790 25

OBS control plane n n The control plane takes charge of establishing a label switch path (LSP) called as Virtual LSP To set up LSP each node collects network topology, resource usage, and updates it’s routing table Each VLSP should be mapped to a wavelength available in each node. This MPLS control plane based OBS is called ‘labeled OBS’ (LOBS) 03/02/05 CEG 790 26

Binding LSP with l 03/02/05 CEG 790 27

Network failure detection in OBS n n Since the control packet arrives early than the data burst, it is possible to detect a network failure early and respond quickly. Also it is easy to localize a network failure, which makes restoration quick 03/02/05 CEG 790 28

Types of network failures n n n Control channel failure Data channel failure Fiber failure Link failure Node failure 03/02/05 CEG 790 29

Fault detection in optical layer n n Monitoring the optical signal quality per wavelength Detecting fiber failure by applying state information per fiber by monitoring the loss of light (LOL) Open Fiber Control (OFC) 03/02/05 CEG 790 30

Fault detection in optical layer n n Link failure is detected when all the fibers in a link change to DISOCNNECT state Node failure is detected by the following 2 conditions q q 03/02/05 Every node exchanges liveliness messages with its neighbor and counts the number of messages periodically to check its normality. If the message count is zero then either it is fiber failure or node failure. CEG 790 31

The interesting part of paper n RESTORATION IN OBS 03/02/05 CEG 790 32

Classification of OBS restorations n Path level restoration q n This is done globally between OBS PSL and OBS PML Link level restoration q q 03/02/05 Results in faster restoration and better utilization If this fails then path level restoration is tried CEG 790 33

OBS restoration procedure 03/02/05 CEG 790 34

Single channel failure (Control channel) 03/02/05 CEG 790 35

Single channel failure (Data channel) Link-level unrestored traffic 03/02/05 CEG 790 36

Both Control & Data channel failure Path level restoration Path-level unrestored traffic 03/02/05 CEG 790 37

Fiber failure Link level restoration 03/02/05 CEG 790 38

Link or Node level failure n n n A larger number of VLSP are required to be restored OPSL may split the restored traffic into several backup paths, these paths should be preplanned If all the above methods fail, the backup path will be dynamically calculated based on the colleted routing information. 03/02/05 CEG 790 39

Link failure and restoration 03/02/05 CEG 790 40

Unrestored traffic n Link-level unrestored traffic q n When a channel or fiber failure occurs, some BCP may have already passed the node and the corresponding data burst will be lost Path-level unrestored traffic q 03/02/05 The data burst arriving before the path-level restoration begins will be lost. CEG 790 41

Restoration of the unrestored traffic n For best-effort service q n The node having the unrestored traffic simply discards it, reducing the complexity of the system. For traffic which require low loss rate q For link-level unrestored traffic n q For path-level unrestored traffic n 03/02/05 The node detecting failure will generate a newly updated BCP, which has new offset time, label, wavelength and failure information It uses “temporary LSP” CEG 790 42

temporary LSP n n n It is used for path-level restoration It is another backup path from the fault detecting node to the OPML for temporary purpose This path is used until the local node completes the path-level restoration after sending FIS to the OPSL The “temporary LSP” will be released after path-level unrestored traffic is restored. How is it implemented … 03/02/05 CEG 790 43

temporary LSP implementation n n Each node needs to reserve a small portion of label space, which will be used when establishing the “temporary LSP” on the fly The node maintains the shortcut path information, keeping it up-to-date. Thus, this scheme can reduce the loss rate and restoration time. Lets see a example … 03/02/05 CEG 790 44

Path-level unrestored traffic Simple path level restoration 03/02/05 CEG 790 45

temporary LSP implementation 03/02/05 CEG 790 46

Problems with temporary LSP n Low utilization and a long restoration time q n It requires the local node detecting fault to send and FIS to OPSL, then OPSL initiates restoration. So for restoring the traffic faster “bossy LSP” is suggested 03/02/05 CEG 790 47

Bossy LSP n n Conceptually, the “bossy LSP” is the same as the “temporary LSP”; however, it is different from the “temporary LSP” in that the latter releases the LSP after “path-level un-restored” traffic is restored, while the former establishes the LSP as a permanent use. It uses preemption attribute q q 03/02/05 When it reserves the label, it can preempt lower priority LSP. If all the labels are used by “bossy LSP” then simple-path level restoration is required. CEG 790 48

Unnecessary resource reservation 03/02/05 CEG 790 49

Simulation model n n n 9 OBS nodes Multiple VLSP connects the nodes 6 VLSP are configured for simulation Traffic is generated in each LSP with a continuous data burst at a constant bit rate. The network topology used is … 03/02/05 CEG 790 50

Network topology 03/02/05 CEG 790 51

Simulation result parameters n Three types of network failures are considered q n n Channel, Fiber, Link Since the restoration time for both channel and fiber failures is too fast to distinguish, we only focus on the case of the link failure. ? ? ? The path-level restoration for the link failure is done using three methods q q q 03/02/05 Simple path-level restoration “temporary LSP” “bossy LSP” CEG 790 52

Simulation results Simple path-level restoration Amount of traffic received at destination node 03/02/05 CEG 790 53

Simulation results temporary LSP restoration 03/02/05 CEG 790 54

Simulation results bossy LSP restoration 03/02/05 CEG 790 55

Comparison 03/02/05 CEG 790 56

Summary n n n We reviewed the existing protection /restoration schemes for both optical networks and IP (MPLS) networks We talked in detail a fault detection technique for all kinds of faults that might occur in the optical Internet. We discussed the pro-posed OBS restoration procedures as well as the concept of the “temporary LSP” and “bossy LSP. ” We also showed that the “temporary LSP” and “bossy LSP” can enhance the fault localization for fast restoration and dramatically reduce loss as well. The “bossy LSP” is better than the “temporary LSP” in the aspect of bandwidth utilization and service continuity. 03/02/05 CEG 790 57

Future work n There is a need for further studies in OBS restoration, specifically, it is necessary to develop an OBS-specific routing algorithm for OBS restoration which meets the following requirements q q 03/02/05 Calculation of a working path with a backup path that can accommodate the maximum number of the future connections. Traffic engineering that can resolve channel contention problems (the FDL limitation) and result in the better network utilization. CEG 790 58