Internet DRAFT - draft-he-ccamp-optimal-routing

draft-he-ccamp-optimal-routing



Network Working Group                                           Peng He 
Internet Draft                                       Gregor v. Bochmann 
Expires: March 2007                                University of Ottawa 
                                                     September 21, 2006 
                                    
 
                                      
           A Novel Framework for Inter-area MPLS Optimal Routing 
                   draft-he-ccamp-optimal-routing-00.txt 


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   This Internet-Draft will expire on March 21, 2007. 

Abstract 

   We propose a novel framework for inter-area MPLS optimal routing. The 
   key to our proposal lies in deploying an overlaid star optical 
   network in the OSPF backbone area and introducing the concept of 
   "virtual area border routers" (v-ABRs). Compared with other 
   proposals, our framework can provide globally optimized inter-area 
   routing and has very good compatibility to existing traditional 
   IP/MPLS routers.  



 
 
 
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Conventions used in this document 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in RFC-2119 [RFC2119]. 

Table of Contents 

   1. Terminology....................................................2 
   2. Introduction...................................................3 
      2.1. What's The Problem........................................3 
      2.2. Current Approaches........................................4 
   3. The Novel Framework for Inter-area MPLS Optimal Routing........5 
      3.1. The Basic Idea............................................5 
         3.1.1. Overview of Agile All-Photonic Network (AAPN)........5 
         3.1.2. Deploying AAPN in the OSPF Backbone Area.............6 
      3.2. The Routing-Info Component................................7 
      3.3. The Path Computation Component............................8 
      3.4. The Signalling Component..................................8 
         3.4.1. Path Message in the Head-End Area....................9 
         3.4.2. Path Message in the Backbone Area....................9 
         3.4.3. Path Message in the Tail-end Area...................10 
         3.4.4. Resv Message........................................10 
   4. Further Considerations........................................11 
   5. Generalization of the Proposed Routing Framework..............12 
   6. Security Considerations.......................................13 
   7. IANA Considerations...........................................13 
   8. Conclusions...................................................13 
   9. Acknowledgments...............................................13 
   10. References...................................................14 
   Author's Addresses...............................................15 
   Intellectual Property Statement..................................15 
   Disclaimer of Validity...........................................16 
   Copyright Statement..............................................16 
   Acknowledgment...................................................16 
    
    

1. Terminology 

   OSPF: Open Shortest Path First 

   CSPF: Constraint-based Shortest Path First 

   LSP:  Label Switched Path 

   LSR:  Label Switched Router 
 
 
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   LSDB: Link State Database 

   RSVP: Resource Reservation Protocol 

   AAPN: Agile All-Photonic Network 

2. Introduction 

   Currently, several carriers have multi-area networks, and many other 
   carriers that are still using a single IGP area may have to migrate 
   to a multi-area environment as their network grows and approaches the 
   single area scalability limits [RFC4105]. Hence, it would be useful 
   and meaningful to extend current MPLS TE (Traffic Engineering) 
   capabilities across IGP areas to support inter-area resources 
   optimization. That is why RFC4105 [RFC4105] was recently published to 
   define detailed requirements for inter-area MPLS traffic engineering 
   and ask for solutions.  

   In this draft, we consider the Open Shortest Path First (OSPF) 
   [RFC2328, RFC3630] IP routing protocol, which is commonly used for 
   routing within a single administrative domain and adopted by MPLS and 
   GMPLS (Generalized MPLS) (with extensions). 

2.1. What's The Problem 

   OSPF supports large networks through multiple OSPF areas: one 
   backbone area (Area0) surrounded by non-backbone areas. Area border 
   routers (ABR) are located at the border between the backbone and the 
   non-backbone areas. 

   An inter-area connection normally starts in a non-backbone area, 
   traverses a backbone area, and terminates in another non-backbone 
   area. MPLS TE mechanisms that have been deployed today by many 
   carriers are limited to a single IGP area and can not be expanded to 
   multi-areas directly. The limitation comes more from the routing and 
   path computation components than from the signalling component. This 
   is basically because the OSPF/OSPF-TE hierarchy limits topology 
   visibility of head-end LSRs (Label Switch Routers) to their area, and 
   consequently head-end LSRs can no longer run a CSPF algorithm to 
   compute the shortest constrained path to the tail-end, as CSPF 
   requires the whole topology information in order to compute an end-
   to-end shortest constrained path.  

   For an example, Figure 1 shows a common multi-area network and we 
   suppose RT1 in Area1 is the source node while RT6 in Area2 is the 
   destination. Generally speaking, a non-backbone area (e.g., Area1 in 
   Figure 1) often has multiple ABRs (existing points). One ABR might be 
 
 
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   much closer to the destination of a requested MPLS connection than 
   another. Because the head-end node does not have the entire topology, 
   it does not know which ABR is the best choice. In Figure 1, how could 
   R1 choose an optimum ABR in Area1 to the destination RT6? Through 
   local optimization, R1 may select ABR2 to be on the path, but how 
   does ABR2 know what the best path is to go to RT6? Although local 
   optimization can be done in each of the respective areas along the 
   inter-area path (RT1 to RT6), the simple summation of the three local 
   optimizations does not necessarily lead to a global optimization. 
   What many carriers want is to optimize their resources as a whole. 
   Therefore, the question of how to implement inter-area routing with 
   global optimization guarantee is a key issue in inter-area traffic 
   engineering. 

2.2. Current Approaches 

   Most current approaches for inter-area routing center on the "how-to" 
   issue, that is, how to find out an inter-area route (not optimal and 
   not dynamic) and how to build up this path through the inter-area 
   signalling process. The per-area approach uses a two-step method to 
   compute an inter-area route: find out a "loose inter-area route" 
   first through topology aggregation/abstraction, then resolve the 
   loose route into a strict path, area by area. Actually, this per area 
   approach would always lead to sub-optimal resource utilization. 
   Another segment approach divides an inter-area path into two 
   segments, one in Area1 and one in Area0 & Area2 (see Figure 1 for a 
   rough look). Optimal routing of the 1st segment is done first by the 
   head-end LSR; then based on the 1st segment, a far-end ABR (e.g., 
   ABR5) computes the 2nd segment. Obviously, this approach can not 
   achieve global route optimization either. PCE (Path Computation 
   Element)-based approaches [PCE-ARC] are the only category of 
   approaches that can provide global optimization. But this needs 
   building up an independent overlay external PCE network that covers 
   all the areas, and defining and implementing many associated new 
   protocols.  












 
 
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      <---------Area1---------><------Area0-------><-------Area2-----> 
       
                      ---    ----                ----     --- 
                     |RT2|--|ABR1|-----...------|ABR4|---|RT6| 
                    / ---    ----                ----   / --- \ 
                   /                                   /       \ 
       ---     ---           ----                ---- /         \ --- 
      |RT1|---|RT3|---------|ABR2|     ...      |ABR5|-----------|RT8| 
       ---     ---           ----                ---- \         / --- 
          \                /                           \       / 
           \ ---      --- /  ----                ----   \ --- /      
            |RT4|----|RT5|--|ABR3|-----...------|ABR6|---|RT7| 
             ---      ---    ----                ----     --- 
    
      - ABR1, ABR2, ABR3: Area0-Area1 ABRs 
      - ABR4, ABR5, ABR6: Area0-Area2 ABRs 
    
           Figure 1 : A common network with multiple OSPF areas. 

3. The Novel Framework for Inter-area MPLS Optimal Routing 

3.1. The Basic Idea 

   In this draft, we propose a novel framework that deploys an overlaid 
   star optical network in the backbone area so as to implement global 
   resource optimization in an efficient and distributed manner. The 
   star topology can help to achieve globally-optimized routing (as 
   explained later), and the overlaid star can provide high reliability. 

   AAPN (Agile All-Photonic Networks) is a representative example of 
   overlaid star optical networks. Hence we use AAPN to represent 
   overlaid star networks in the following context of this draft. 

3.1.1. Overview of Agile All-Photonic Network (AAPN)  

   As shown in Figure 2, an AAPN [AAPN-ARC] consists of a number of 
   hybrid photonic/electronic edge nodes connected together via several 
   (not less than two) load-balancing core nodes and optical fibers to 
   form an overlaid star topology. Note that there are no direct 
   physical links among these cores. By introducing concentrating 
   devices, AAPN can support up to 1024 edge nodes [AAPN-TOP]. Each core 
   node contains a stack of bufferless transparent photonic space 
   switches (one for each wavelength). A scheduler at each core node is 
   used to dynamically allocate timeslots over the various wavelengths 
   to each edge node. An edge node contains a separate buffer for the 
   traffic destined to each of the other edge nodes. Traffic aggregation 
   is performed in these buffers, where packets are collected together 
 
 
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   in fixed-size slots (sometimes called bursts) that are then 
   transmitted as single units across the AAPN via optical links. At the 
   destination edge node the slots are partitioned, with reassembly as 
   necessary, into the original packets that are sent to the outside 
   routers. The term "agility" in AAPN describes its ability to deploy 
   bandwidth on demand at fine granularity, which radically increases 
   network efficiency and brings to the user much higher performance at 
   reduced cost.  

                         ---     --- 
                        |EN3|---|RT8| 
                         ---     --- 
                         | | 
       ---               | v                  --- 
      |RT1|              | to CN2           /|RT4| 
       --- \  ---        -----        ---  /  --- 
            \|EN1|------| CN1 |------|EN4|/ 
            / --- \    /|     |\    / --- \ 
      ---  /       \  /  -----  \  /       \  ---         
     |RT2|/         \/           \/         \|RT5| 
      ---           /\           /\         / --- 
                   /  \  -----  /  \       / 
              --- /    \| CN2 |/    \ --- / 
             |EN2|------|     |------|EN5| 
       ---  / ---        -----        --- \ 
      |RT3|/   |          | to CN1         \ --- 
       ---     |          | ^               |RT6| 
              ---         | |                --- 
             |RT7|        --- 
              ---        |EN6| 
                          --- 
      - CN:  Core Node 
      - EN:  Edge Node  
      - RT:  Router 
       
   Figure 2 : Agile All-Photonic Network (AAPN) Overlaid Star Topology. 

3.1.2. Deploying AAPN in the OSPF Backbone Area 

   AAPN is more suitable to be used in multi-area network environment 
   due to its agility at the core and large capacity. The direct and 
   natural way to deploy an AAPN in the OSPF backbone area is like this: 
   the core nodes are located in the middle of Area0 and the edge nodes 
   act as ABRs at the border between Area0 and other non-backbone areas. 
   However, in this scheme, inter-area routing with global optimization 
   still can not be guaranteed. Therefore, we adopt a novel way of 
   deploying OSPF over an AAPN that interconnects several OSPF areas to 
 
 
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   provide such guarantee, as shown in Figure 3. This "overlapped" OSPF 
   architecture is fundamental for our inter-area MPLS optimal routing 
   framework. In details, our proposed framework consists of three main 
   components, namely the routing-info, path computation and signalling 
   components, as described in the following sections. 

   Note: due to the symmetric architecture of AAPN (see Fig. 2), we use 
   the "bundle" [RFC4201] concept to further reduce the overhead traffic 
   to the outside. That is, all the links from one edge node to the core 
   nodes are exported as one TE link. Similarly, the overlaid core nodes 
   in AAPN are, if necessary, exported as one core node, named as "the 
   core" (see Figure 3). 

   <--------------Area1-----------------><-----------Area2----------> 
                             <---------Area0--------> 
    
                      ---    ----                ----     --- 
                     |RT2|--|EN1 |              |EN4 |---|RT6| 
                    / ---    ---- \            / ----   / --- \ 
                   /               \  ------  /        /       \ 
     ---      --- /          ----   \| THE  |/   ---- /         \ --- 
    |RT1|----|RT3|----------|EN2 |---| CORE |---|EN5 |-----------|RT8| 
     --- \    ---          / ----   /|      |\   ---- \         / --- 
          \               /        /  ------  \        \       / 
           \ ---     --- /   ---- /            \ ----   \ --- /      
            |RT4|---|RT5|---|EN3 |              |EN6 |---|RT7| 
             ---     ---     ----                ----     --- 
                              
    <-------------sub-path1-------------><--------sub-path2----------> 
    
      Figure 3 : Our framework deploys AAPN as backbone area (Area0). 

3.2. The Routing-Info Component 

   This component is responsible for the discovery of the TE topology, 
   which can be ensured through OSPF [RFC2328] and OSPF-TE [rfc3630]. As 
   shown in Figure 3, after deploying AAPN as backbone area, we further 
   expand the OSPF non-backbone areas a little step so that there is an 
   overlap between Area0 and each expanded non-backbone area. Then the 
   AAPN edge nodes located in the overlap (see the top of Figure for the 
   overlap), together with their direct TE links to the core, and the 
   associated part of the core, belong to both the Area0 and a non-
   backbone area. In such a scenario, legacy routers in a non-backbone 
   area see related AAPN edge nodes as normal internal IP/MPLS routers, 
   see the AAPN TE links as normal internal links and see the associated 
   part of the core as the (only) ABR of their non-backbone area. In 
   other words, a legacy router sees what it can see in its area about 
 
 
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   the core as an ABR, which we call a virtual-ABR (v-ABR). For each 
   legacy router in an expanded non-backbone area, the exchange and 
   distribution of routing/TE information is just like in any other 
   standard OSPF/OSPF-TE area.  

   While within the Area0 (within the AAPN), the AAPN edge nodes that 
   belong to the same non-backbone area can be organized as a big 
   virtual router and one edge node in each virtual router is selected 
   as the head of this virtual router. Then the area-specific 
   reachability information is exchanged among these heads and 
   distributed to each edge node per area and then outside routers. 
   Therefore, it is the head edge node that actually performs the 
   functions of the virtual-ABR, that is, distributing area-specified 
   reachability information. Note that only the reachability (not TE) 
   information, which is enough for our framework, is exchanged among 
   virtual routers, and hence among non-backbone areas.  

3.3. The Path Computation Component 

   In our framework, an inter-area LSP can be considered consisting of 
   two segments as shown in the bottom Figure 3: one in the head-end 
   (expanded) area (sub-path1) and one in the tail-end (expanded) area 
   (sub-path2). The core connects these two segments/sub-LSPs to form a 
   complete inter-area LSP. 

   The most interesting thing is that local routing optimization 
   (through CSPF) with both of these two sub-LSPs can lead naturally to 
   a globally-optimized inter-area LSP. As seen in Figure 3, this is due 
   to the particular star topology of the AAPN architecture and the 
   load-sharing core nodes that can be viewed as one single virtual 
   router (v-ABR) from the outside. 

   The local routing optimization in the head-end area can be performed 
   by the source LSR, which takes the TE topology and LSP constraints as 
   input. While in the tailend area, local routing optimization is done 
   by one of the edge nodes in the area (see next section for details). 
   Obviously, dynamic inter-area routing can be implemented in our 
   proposed framework. 

3.4. The Signalling Component 

   This component is responsible for the establishment of the LSP along 
   the computed path. In Figure 3, consider the case that a source LSR 
   (RT1) in Area1 wants to set up a LSP to a destination LSR (RT8) in 
   Area2. RT1 must first compute an optimized path to the virtual-ABR of 
   Area1 (v-ABR1) through CSPF, and then signal this establishment 

 
 
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   request to the network. RSVP with TE extension (RSVP-TE) [RFC2205, 
   RFC3209] can be used as the signalling protocol. 

3.4.1. Path Message in the Head-End Area 

   As shown in Figure 4, RT1 starts the signalling process by creating a 
   RSVP Path message with two objects inserted, namely LABEL_REQUEST 
   Object (LRO) to request a label binding for the path, and 
   EXPLICIT_ROUTE object(ERO) to indicate the computed explicit path 
   (with one sub-object per hop). However, RT1 has to use the loose ERO 
   sub-objects for the hops outside Area1. In Figure 3, the ERO 
   specifies the explicit path as RT1->RT3->EN2->v-ABR1->RT8, where RT8 
   is a loose ERO sub-object. Then, RT1 sends the Path message to the 
   next hop defined in the ERO, which is RT3. 

   RT3 (a non AAPN node) receives the Path message and processes it as 
   defined by RSVP-TE: 

   1. Checks the message format to make sure everything is OK, 

   2. Performs admission control to check the required bandwidth, 

   3. Stores the "path state" from the Path message in its local Path 
      State Block (PSB) to be used by the reverse-routing function, and 

   4. If successful, deletes the 1st sub-object (itself) in the ERO and 
      forwards the Path message according to the new 1st sub-object 
      (next hop) in the ERO, in our case, EN2. 

3.4.2. Path Message in the Backbone Area 

   EN2, an AAPN edge node, receives the Path message from RT3 and checks 
   the contained ERO. If EN2 finds that the IP address of the 2nd sub-
   object in the ERO is a v-ABR and the 3rd sub-object (with the loose 
   attribute) is beyond Area1, then EN2 has the task of resolving the 
   loose sub-object into strict ones. In our case, there is one loose 
   sub-object, RT8, which represents the destination of the requested 
   LSP. Although EN2 can not find a strict path from v-ABR1 to RT8 by 
   itself, it knows who can. First, by checking the inter-area 
   reachability information and internal parameters, EN2 finds out which 
   group of edge nodes (also which associated v-ABR) locates in the same 
   non-backbone area as RT8. In Figure 4, these are EN4, EN5 and EN6 (v-
   ABR2). Second, it selects an edge node among them randomly, e.g., 
   EN4. In the third step, EN2 removes the first two sub-objects (itself 
   and v-ABR #1) from the ERO of the original received Path message, and 
   inserts v-ABR2 at the top, then forwards the modified Path message to 
   EN4. 
 
 
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   When EN4 receives the Path message and finds that the 1st sub-object 
   in the received ERO is v-ABR2, together with a loose second sub-
   object, RT8, it knows that it should find an explicit path between 
   these two sub-objects. As shown in Figure 3, EN4 is capable to do the 
   resolving work because EN4 and RT8 reside in the same expanded area, 
   Area2. EN4 finds the optimized explicit path v-ABR2->EN5->RT8. EN4 
   then replaces the ERO object in the received Path message with a new 
   ERO object that stores the resolved explicit route (EN5->RT8). 
   Finally, EN4 forwards the new modified Path message to EN5 as if it 
   were forwarded from EN2 by using EN2's data (IP address, etc.). We 
   call this process a Path message handoff. At the same time, EN5 also 
   sends an acknowledge message (containing the resolved path) to EN2 
   (Figure 5). From the above handoff process, we can see that only the 
   area-specific reachability (not TE) information needs to be exchanged 
   among areas. In our proposal, TE information is organized within each 
   area. 

3.4.3. Path Message in the Tail-end Area 

   The edge node EN5 receives the Path message and believes it is from 
   EN2. Since all the sub-objects in the received ERO are strict, EN5 
   processes this Path message in a standard way, just as RT3 did in 
   Area1, and then forwards the processed Path message to RT8. 

3.4.4. Resv Message 

   When the destination, RT8, gets the Path message, it responds to this 
   establishment request by sending a RSVP Resv message. The purpose of 
   this response is to have all routers along the path perform the Call 
   Admission Control (CAC), make the necessary bandwidth reservations 
   and distribute the label binding to the upstream router. 

   As defined in standard ESVP-TE [RFC3209], the label is distributed 
   using the Label Object in the Resv message. The labels sent upstream 
   become the output labels for the routers receiving the label object. 
   The label that a router issues upstream become the inbound label used 
   as the lookup into the hardware output tag table. The reservation-
   specific information is stored in the local reservation state block 
   (RSB) of each router. 

   When the AAPN edge node EN5 receives the Resv message from downstream 
   (RT8), it starts internal AAPN signalling to ask the core to set-up a 
   connection from EN2 to EN5 (omit v-ABR1&2). If bandwidth is available 
   for this connection, the core informs both EN2 and EN5. EN5 then 
   sends a Resv message to EN1. Note that it is an internal choice of 
   the AAPN to select a label, for instance, a timeslot number, a 
   wavelength, or a normal MPLS label. 
 
 
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   The Resv message makes its way upstream (see Figure 4), hop by hop, 
   and when it reaches the source LSR, RT1, the inter-area path is set-
   up as: RT1->RT3->EN2->v-ABR1->v-ABR2->EN5->RT8. Now, a globally 
   optimized inter-area LSP is set-up. It can be maintained and torn-
   down just as any normal intra-area LSP tunnel. 

     <-------------Area1---------------><------------Area2----------> 
                             <--------Area0--------> 
                                                ----      
                                               |EN4 | 
                                      ------  / ----       
     ---      ---            ----    | THE  |/   .    ----        --- 
    |RT1|----|RT3|----------|EN2 |---| CORE |--------|EN5 |------|RT8| 
     ---      ---            ----    |      |    .    ----        --- 
      .                       .       ------     .       .          . 
   .  .                       .                  .       .          . 
   .  .PATH======341=========>.                  .       .          . 
   t  .                       .PATH===342=======>.       .          . 
   i  .                       .<=================.=Hand=>.          . 
   m  .                       .                  .  off  .          . 
   e  .                       .                  .       .PATH=343=>. 
   .  .                       .                  .       .          . 
   .  .                       .                          .<=344=RESV. 
   v  .                       .<=========344=========RESV.          . 
      .<=========344======RESV.                          .          . 
    
   Figure 4 : Inter-area LSP Signaling Process.(34x means Section 3.4.x) 

4. Further Considerations 

   Contrary to other inter-area proposals, our proposal can provide 
   globally-optimized inter-area routing and does not require any 
   changes on existing traditional IP/MPLS routers, hardware or 
   software, to implement (good backward compatibility). Furthermore, 
   there is no node that has global TE information. Instead, the TE 
   information is distributed on a per-area basis and only area-specific 
   reachability (not TE) information is exchanged among areas. Global 
   optimization is achieved through cooperation and interaction between 
   AAPN edge nodes in different areas (Path message handoff). In 
   addition, for the 2nd half of an inter-area LSP (in the tail-end 
   area), the optimized routing computation is done by an AAPN edge node 
   randomly chosen in the tail-end area. Hence, load-sharing among these 
   edge nodes is achieved. 

   Under our proposed framework, inter-area routing can be dynamic. In 
   addition, re-optimization of an inter-area TE LSP can also be 
   implemented, either locally within an area (by the head-end LSR for 
 
 
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   the 1st half or by an edge node for the 2nd half of LSP) or globally 
   by the head-end LSR (end-to-end re-optimization). 

   Regarding inter-area QoS, there is not much work left. Current single 
   area QoS mechanisms [RFC2475, RFC 3270] can be expanded directly to 
   multiple areas and to AAPN. 

   As seen in Figure 3, our proposal keeps OSPF's hierarchical structure 
   and just expands non-backbone areas a little. Hence the scalability 
   of our proposal is as good as OSPF/OSPF-TE [RFC2328, RFC3630]. 

   Our proposed framework also supports diversely-Routing of inter-area 
   TE LSPs, as required in RFC4105 [RFC4105]. As shown in Figure 3, 
   diversely routing can be deployed in Area 1 and 2 independently and 
   optimally, and then the AAPN residing in the backbone area connects 
   them together. 

5. Generalization of the Proposed Routing Framework 

   The routing concepts discussed in this draft are based on the 
   assumption that there are a number of edge nodes (that are connected 
   with other routers - through traditional Internet technology - and 
   belonging to the same OSPF area) and these edge nodes can establish 
   optical connections between one another in an agile manner and can 
   adjust the bandwidth of each connection in an agile manner according 
   to the varying bandwidth that is required by the IP traffic. We think 
   any agile optical switching technology (burst switching, TDM (Time- 
   Division-Multiplexing), or routed wavelength (with less bandwidth 
   flexibility)) may be used. 

   Our proposal is not limited to AAPNs, it is actually applicable in a 
   much larger context. The fundamental ideas abstracted from our 
   proposal are: (1) a "load-symmetrical" network (optical mostly) as 
   backbone, (2) overlap between backbone and non-backbone areas, and 
   (3) virtual-ABR. A load-symmetrical optical network is a network that 
   can provide one or several optical connections for each edge node 
   pair (source-destination pair) and the load among the several optical 
   connections of each edge node pair is balanced. Hence the "bundle" 
   concept [5] can be used and a single core can represent the optical 
   network topology. 

   Note that "load-symmetrical" does not mean the loads among any 
   distinct edge node pairs are balanced; it only refers to the load-
   balancing within the connections of one edge node pair. Load 
   symmetrical networks do not need to have a symmetrical physical 
   network topology, although a symmetrical physical network topology 

 
 
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   (such as AAPN] and PON (Passive Optical Networks)) can be made load-
   symmetrical easily. 

6. Security Considerations 

   This document does not introduce new security issues beyond those 
   inherent in MPLS TE [RFC3209, rfc3630]. 

7. IANA Considerations 

   This informational document makes no requests for IANA action. 

8. Conclusions 

   Based on deploying a load-symmetrical network (such as an overlaid 
   star optical network (AAPN)) in multi-area networks, we propose a 
   novel framework that aims to implement optimal inter-area MPLS 
   routing. 

   Compared with other inter-area routing proposals, our proposal has 
   two distinguishing characteristics: 

   1. Our proposal can provide globally-optimized inter-area routing; 

   2. There will be no change, hardware or software, on existing 
      traditional IP/MPLS routers in the peripheral OSPF areas to 
      implement our proposal. 

   Furthermore, our proposal is not limited to AAPNs; it is actually 
   applicable to any load-symmetrical (optical) network with arbitrary 
   physical network topology. Indeed, our proposal can be considered as 
   a highly competitive candidate that has the potential to become a 
   total solution to Inter-area MPLS Traffic Engineering [RFC4105]. 

9. Acknowledgments 

   This work was supported by the Natural Sciences and Engineering 
   Research Council (NSERC) of Canada and industrial and government 
   partners, through the Agile All-Photonic Networks (AAPN) Research 
   Network. This work is part of an AAPN Partnered Research Project 
   sponsored by TELUS. The authors thank Rainer Iraschko for useful 
   discussions. 





 
 
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10. References 

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 
             Requirement Levels", BCP 14, RFC 2119, March 1997. 

   [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. 
             Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 
             Functional Specification", RFC 2205, September 1997. 

   [RFC2328] J. Moy, "OSPF Version 2", RFC 2328, April, 1998. 

   [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 
             and W. Weiss, "An Architecture for Differentiated Service", 
             RFC 2475, December 1998. 

   [RFC3209] Awduche, D., et al. "RSVP-TE: Extensions to RSVP for LSP 
             Tunnels", RFC 3209, December, 2001. 

   [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S.,Vaananen, 
             P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-
             Protocol Label Switching (MPLS) Support of Differentiated 
             Services", RFC 3270, May 2002. 

   [RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering 
             Extensions to OSPF Version 2", RFC 3630, September, 2003. 

   [RFC4105] Le Roux, et al., "Requirements for Inter-Area MPLS Traffic 
             Engineering", RFC 4105, June 2005. 

   [RFC4201] K. Kompella et al. "Link Bundling in MPLS Traffic 
             Engineering (TE)" RFC 4201, October, 2005. 

   [PCE-ARC] Farrel, A., "A Path Computation Element (PCE) Based 
             Architecture", draft-ietf-pce-architecture-04 (work in 
             progress), January 2006. 

   [AAPN-ARC]G. v. Bochmann, M.J. Coates, T. Hall, L. Mason, R. Vickers 
             and O. Yang, "The Agile All-Photonic Network: An 
             architectural outline", Proc. Queen's University, Biennial 
             Symposium on Communications, 2004, pp.217-218. 

   [AAPN-TOP]L.G. Mason, A. Vinokurov, N. Zhao and D. Plant, 
             "Topological Design and Dimensioning of Agile All Photonic 
             Networks", Computer Networks: The International Journal of 
             Computer and Telecommunications Networking, Volume 50, 
             Issue 2(February 2006), Pages: 268 - 287, 2006. 

 
 
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Author's Addresses 

   Peng He 
   School of Information Technology and Engineering (SITE) 
   University of Ottawa 
   800 King Edward Avenue 
   Ottawa, Ontario 
   K1N 6N5 Canada 
       
   Phone: 1-613-5625800 ext. 2191 
   Email: penghe@site.uottawa.ca 
    

   Gregor v. Bochmann 
   School of Information Technology and Engineering (SITE) 
   University of Ottawa 
   800 King Edward Avenue 
   Ottawa, Ontario 
   K1N 6N5 Canada 
       
   Phone: 1-613-5625800 ext. 6205 
   Email: bochmann@site.uOttawa.ca 
    

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Acknowledgment 

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