One document matched: draft-jiang-l2vpn-vpls-mac-operation-00.txt


Network Working Group                                       Y.L., Jiang 
Internet Draft                                                 Y., Yang 
                                                                 Huawei 
Intended status: Standards Track                          June 24, 2008 
Expires: December 24, 2008 
                                    
 
                                      
         Optimized MAC Address Operations in VPLS with Redundancy 
               draft-jiang-l2vpn-vpls-mac-operation-00.txt 


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   This Internet-Draft will expire on December 24, 2008. 

Copyright Notice 

   Copyright (C) The IETF Trust (2008). 

Abstract 

   The Virtual Private LAN Service (VPLS) Using Label Distribution    
   Protocol (LDP) Signaling is described in RFC 4762. That document   
   describes a mechanism called MAC Address Withdrawal to remove or    
   unlearn MAC addresses which have been dynamically learned in a VPLS   
 
 
 
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   instance. Further work in progress defines an extension to MAC 
   Address Withdrawal procedure which can greatly restrict the scope of 
   MAC flushing. This document provides two mechanisms which completely 
   remove the need for MAC address flushing in VPLS instances. The 
   mechanisms are MAC address switching and MAC address notification.    

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. Introduction...................................................2 
   2. Scenarios......................................................3 
   3. Optimized MAC Address Operations...............................5 
      3.1. MAC Address Switching.....................................6 
      3.2. MAC Address Notification..................................6 
   4. LDP Extensions.................................................6 
      4.1. PW-ID TLV.................................................6 
      4.2. MAC Address Switching Message.............................9 
      4.3. MAC Address Notification Message.........................10 
   5. Signaling MAC Address Operations..............................11 
   6. Processing Rules..............................................11 
      6.1. Receipt of MAC Address Switching Message.................11 
      6.2. Receipt of MAC Address Notification Message..............12 
   7. Applicability.................................................12 
   8. Security Considerations.......................................12 
   9. IANA Considerations...........................................14 
      9.1. New LDP Message Types....................................14 
      9.2. New LDP TLV Type.........................................14 
   10. Acknowledgments..............................................14 
   11. References...................................................15 
      11.1. Normative References....................................15 
      11.2. Informative References..................................15 
   Author's Addresses...............................................15 
   Intellectual Property Statement..................................16 
   Disclaimer of Validity...........................................16 
    
    

1. Introduction 

   A method of Virtual Private LAN Service (VPLS), also known as 
   Transparent LAN Service (TLS) is described in [RFC4762]. A VPLS is 
 
 
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   created using a collection of one or more point-to-point pseudowires 
   (PWs) [RFC4664] configured in a flat, full-mesh topology. The mesh  
   topology provides a LAN segment or broadcast domain that is fully  
   capable of learning and forwarding on Ethernet MAC addresses at the  
   PE devices.    

   A MAC Address Withdrawal mechanism is described in [RFC4762] to 
   remove or unlearn MAC addresses for faster convergence on topology 
   change [RFC4762]. But when a PE device in VPLS receives a MAC Flush 
   message it may also flush the MAC addresses which are not affected 
   by the topology change, thus leading to unnecessary flooding and MAC 
   relearning. [MAC-OPT] describes a solution to optimize the MAC flush 
   procedure so that only the MAC addresses affected by topology change 
   are flushed. This can greatly restrict the scope of MAC flushing.  

   Both of the methods provided by [RFC4762] and [MAC-OPT] must flush 
   the MAC addresses first, and then re-learn them by flooding all 
   frames with these MAC addresses as layer 2 destinations. This incurs 
   a waste of bandwidth and may even cause congestions in the MPLS core 
   network. 

   For PW switching scenarios introduced in [MAC-OPT] and [PW-RED], 
   when a working PE switches to a backup PE or a working PW switches 
   to a backup PW, its associated MAC address could be re-utilized 
   rather than flushed. 

   This document provides two mechanisms which completely remove the   
   need for MAC address flushing in VPLS instances. The mechanisms are   
   MAC address switching and MAC address notification. 

2. Scenarios 

   Figure 1 demonstrates the VPLS reference model as explained in 
   [RFC4664]. PE devices that are VPLS-capable provide a logical 
   interconnect such that Customer Edge (CE) devices belonging to a 
   specific VPLS appear to be on a single bridged Ethernet. From Figure 
   1, we see that in a VPLS, a CE device attaches, possibly through an 
   access network, to a "bridge" module of a VPLS PE. Within the VPLS 
   PE, the bridge module attaches, through an "Emulated LAN Interface", 
   to an Emulated LAN.  For each VPLS, there is an Emulated LAN 
   instance.   

   Figure 1 shows some internal structure to the Emulated LAN: it 
   consists of "VPLS Forwarder" modules connected by PWs, where the PWs 
   may travel through Packet Switched Network (PSN) tunnels over a 
   routed backbone. A "VPLS instance" consists of a set of VPLS 
   Forwarders (no more than one per PE) connected by the PWs in a full-
 
 
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   mesh configuration. Both the "bridge" and the "VPLS Forwarder" 
   should maintain forwarding tables that map MAC addresses to ACs or 
   PWs (they may be combined into a single table). The VPLS "bridge" 
   does MAC Source Address (SA) learning on frames received on ACs, 
   while the "VPLS Forwarder" does SA learning on PWs. 

                              |-----Routed Backbone---| 
                              |     (P Routers)       |PSN Tunnels, 
        Emulated LAN          |                       |Pseudowires 
   ..................................................................... 
   .                       |                       |                   . 
   . |---------------------|----|         |--------|-----------------| . 
   . | --------------------|--- |         | -------|---------------- | . 
   . |      VPLS Forwarder      |         |      VPLS Forwarder      | . 
   . | ----------|------------- |         | ----------|------------- | . 
   ..|...............................................................|.. 
     |           | Emulated LAN |         |           | Emulated LAN | 
     |           | Interface    |VPLS-PEs |           | Interface    | 
     |           |              |  <--->  |           |              | 
     | ----------|------------  |         | ----------|------------  | 
     | |       Bridge        |  |         | |       Bridge        |  | 
     | -|--------|----------|-  |         | -|--------|----------|-  | 
     |--|--------|----------|---|         |--|--------|----------|---| 
        |        |          |                |        |          | 
        |        | Access   |                |        | Access   | 
        |        | Networks |                |        | Networks | 
        |        |          |                |        |          | 
        |        |          |                |        |          | 
                CE devices                              CE devices 
    
                        Figure 1 VPLS Architecture 

   Figure 2 describes a dual-homed H-VPLS scenario for a VPLS instance 
   where the proposed mechanisms can be applied.  

   In Figure 2, the Multi-Tenant Unit switch (MTU-s) is dual-homed to 
   PE-1 and PE-2. Only the primary spoke PW is active at MTU-s, thus 
   PE-1 acting as the primary device to reach the full mesh in the VPLS 
   instance. The MAC addresses located at customer sites (behind CE1 
   and CE2) are learned at PE-1 over the primary spoke PW. PE-2, PE-3 
   and PE-4 learn those MAC addresses on their respective mesh PWs 
   terminating at PE-1 (PW5, PW1, PW3). This is all as described in    
   [RFC4762].  

   When MTU-s switches to the backup spoke PW and activates it, PE-2 
   becomes the primary device to reach the full mesh core. Traffic 
   entering the H-VPLS from CE-1 and CE-2 is diverted by MTU-s to the 
 
 
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   backup spoke PW, and then transferred across the full mesh core to 
   remote PE-3 or PE-4 by way of PW2 or PW4. For faster convergence 
   MTU-s may send a MAC flush message to PE-2 once the backup PW has 
   been made active, and PE-2 forwards the MAC flush message to PE-3 
   and PE-4. In this way, both [RFC4762] and [MAC-OPT] mechanisms will 
   flush MAC addresses associated with PW1 from PE-3, and those MAC 
   addresses associated with PW3 from PE-4. The addresses will be re-
   learned by flooding frames with these MAC addresses as their 
   destinations. Additionally, PE-2 will have to re-learn the MAC 
   addresses behind customer sites CE-3 and CE-4 which PE-1 had 
   previously learnt from PW1 and PW3 respectively.     

                                PE-1                       PE-3        
                              +--------+                +--------+     
                              |        |                |        |     
                              |   --   |           PW1  |   --   | CE-3     
                              |  /  \  |----------------|  /  \  |--->   
    CE-1               /------|  \ s/  |           PW2  |  \S /  |     
      \     primary spoke PW  |   --   |         /------|   --   |     
       \             /        +--------+        /       +--------+     
        \    (MTU-s)/              |    \      /             |         
         +--------+/               |     \    /              |         
         |        |                |      \  /               |         
         |   --   |                |       \/                |         
         |  /  \  |             PW5|   H-VPLS Full Mesh Core |         
         |  \S /  |                |      /  \               |         
         |   --   |                |     /    \              |         
        /+--------+\               |    /      \             |         
       /     backup spoke PW       |   /        \   PW3      |         
      /              \        +--------+         \------+--------+     
     CE-2             \       |        |                |        |     
                       \------|  --    |            PW4 |  --    | CE-4     
                              | /  \   |----------------| /  \   |--->   
                              | \s /   |                | \S /   |     
                              |  --    |                |  --    |     
                              +--------+                +--------+     
                                PE-2                       PE-4 
                                                                                
         Figure 2  Dual homed MTU-s in two tier hierarchy H-VPLS   

    

3. Optimized MAC Address Operations 

   Two mechanisms for optimized MAC address operation are described in 
   this document, the first is MAC address switching, which can be used 
   by a PE node where both the working PW and the backup PW terminate 
 
 
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   at the same PE; the other is MAC address notification, which can be 
   used when the working PW and the backup PW originate from two 
   different nodes (i.e. when a primary PE node switches the VPLS 
   service to a backup PE node). With these two mechanisms, flushing of 
   MAC address can be totally avoided under network scenarios such as 
   figure 2. 

3.1. MAC Address Switching 

   The basic principle of MAC Address Switching is explained with 
   reference to Figure 2. When PW1 is switched to the backup PW2 (PW 
   switching may be realized in a mechanism described in [PW-RED] or in 
   some other way), PE-1 or PE-2 sends out a ''MAC Address Switching'' 
   message to PE-3, and accordingly PE-3 changes its MAC table items 
   with PW1 as the outgoing PW, to show PW2 as the outgoing PW. In this 
   way, remote VPLS peer node PE-3 needs no MAC flushing and re-
   learning, and faster convergence is realized. The message format and 
   the procedure of processing are defined in section 4. 

3.2. MAC Address Notification 

   The basic principle of MAC Address Notification is explained with 
   reference to Figure 2. When PE-1 notifies PE-2 to transfer the VPLS 
   service, it notifies PE-2 of the MAC addresses it leant over the 
   working pseudowire PW1 and PW3. In this way PE-2 does not need to 
   re-learn them over PW2. 

   To facilitate MAC table maintenance on PE-2, the MAC Address 
   Notification messages should include the outgoing PWs to be 
   associated with the notified MAC addresses. Multiple PWs and their 
   associated MAC addresses may be carried in a single message or in 
   separate messages. 

4. LDP Extensions 

   In order to realize MAC address switch and MAC address notification 
   mechanisms, some LDP extensions are defined in this document.   

4.1. PW-ID TLV 

   The PW-ID TLV carries the unique identifier of a PW. The encoding of 
   PW-ID TLV follows standard LDP TLV encoding in [RFC5036], its 
   encoding is: 




 
 
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   0                   1                   2                   3     
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |1|0|  PW-ID  TLV (0x0406)      |            Length             |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |                         PW-ID Element                         |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+             
                                                                                
                           Figure 3  PW-ID TLV 

   U (Unknown) bit of PW-ID TLV MUST be set to 1. If the PW-ID TLV is 
   not understood then it is silently ignored.   

   F (Forward) MUST be set to 0. Since the LDP mechanism used here is 
   targeted, the TLV is not forwarded if it is not understood by the 
   receiving device.  

   The Type field MUST be set to 0x406 (subject to IANA approval). This 
   identifies the TLV type as PW-ID TLV. 

   Length field specifies the total length in octets of the Value in 
   the PW-ID TLV.  

   PW-ID Element encoding depends on the type of the PW-ID Element. A 
   PW-ID Element uniquely identifies a PW. A PW-ID Element value is 
   encoded as 1 octet field that specifies the element type, 1 octet 
   field that identifies the length in octets of the element value, and 
   a variable length field that is a type-dependent element value.   

   The PW-ID Element value encoding is:  

   PW-ID Element      Type              Length             Value  
   Type name  
   FEC-128 specific   0x01            2 octets           See below.  
   FEC-129 specific   0x02            Variable           See below.   
    
   The type of PW-ID Element depends on the type of FEC Element used to 
   provision the respective PW. [RFC4447] defines two types of FEC 
   element that may be used for provisioning PWs - PWid FEC (type 128) 
   and the Generalized ID (GID) FEC (type 129). The PWid FEC element 
   includes a fixed-length 32 bit value called the PWid. The same PWid 
   value must be configured on the local and remote PE prior to PW 
   setup.   

   The GID FEC element includes TLV fields for attachment individual 
   identifiers (AII) that, in conjunction with an attachment group 
   identifier (AGI), serve as PW endpoint identifiers. The endpoint 
 
 
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   identifier on the local PE (denoted as <AGI, source AII or SAII>) is 
   called the source attachment identifier (SAI) and the endpoint 
   identifier on the remote PE (denoted as <AGI, target AII or TAII>) 
   is called the target attachment identifier (TAI). The SAI and TAI 
   can be distinct values. This is useful for provisioning models where 
   the local PE (with a particular SAI) does not know and must somehow 
   learn (e.g. via MP-BGP auto-discovery) of remote TAI values prior to 
   launching PW setup messages towards the remote PE.   

   FEC-128 specific PW-ID Element  

     This sub-type is to be used to identify a PW endpoint only if PWid 
   FEC Element is used for signaling the PW. The encoding of this PW-ID 
   element is as follows:         

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |     0x01      |    Length     |           PW type             |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |                           PW ID                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   
                 Figure 4  FEC-128 specific PW-ID Element     

       PW type  

           The PW Type value from PWid FEC element.  

       PW ID  

           The PW ID value from the PWid FEC element.  

   FEC-129 specific PW-ID element  

       This sub-type is to be used to identify a PW only if GID FEC 
   Element is used for signaling the PW. The encoding of this PW-ID 
   element is as follows:         

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |     0x02      |    Length     |           PW type             |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |                           AGI TLV                             |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   
   |                           SAII TLV                            |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                           TAII TLV                            |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    

                 Figure 5  FEC-129 specific PW-ID Element   
 
 
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       PW type  

           The PW Type value from GID FEC element. 

       AGI TLV  

           The AGI from the corresponding GID Element  

       SAII TLV  

           The SAII associated with the PW. 

       TAII TLV  

           The TAII associated with the PW. 

4.2. MAC Address Switching Message 

   0                   1                   2                   3    
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |0|  Address Switching (0x0302) |      Message Length           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                          Message ID                           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   |                         MAC List TLV                          | 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   |                           PW-ID TLV                           | 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 

                 Figure 6  MAC Address Switching Message 


   Message Type, this field identifies the type of LDP message "Address 
   Switching" and MUST be set to 0x0302. This value needs IANA approval. 

   Message Length, Specifies the cumulative length in octets of the 
   Message ID, MAC list TLV, and PW-ID TLV. 

   Message ID, a 32-bit value used to identify this message. 

   MAC List TLV, this field is defined in section 6.2.1 of [RFC4762]. 

 
 
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   PW-ID TLV, this field is defined in section 4.1 of this document. 

4.3. MAC Address Notification Message 

   A new "MAC Address Notification" message is defined which includes a 
   MAC List TLV as defined in [RFC4762] and a PW-ID TLV as defined in 
   section 4.1 of this document. Multiple MAC List TLVs and PW-ID TLVs 
   MAY be included, and they MUST appear in pairs with the MAC List TLV 
   first. The detailed MAC Address Notification message is explained 
   here. 

   0                   1                   2                   3    
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |0|Address Notification (0x0303)|      Message Length           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                          Message ID                           | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   |                         MAC List TLV                          | 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   |                           PW-ID TLV                           | 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 

                Figure 7  MAC Address Notification Message 


   Message Type, this field identifies the type of LDP message "Address 
   Notification" and MUST be set to 0x0303. This value needs IANA 
   approval. 

   Message Length, Specifies the cumulative length in octets of the 
   Message ID, MAC list TLV, and PW-ID TLV. 

   Message ID, 32-bit value used to identify this message. 

   MAC list TLV, this field is defined in section 6.2.1 of [RFC4762]. 

   PW-ID TLV, this field is defined in section 4.1 of this document. 

   Multiple pairs of MAC List and PW-ID TLVs MAY be present. 



 
 
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5. Signaling MAC Address Operations 

   MAC address notification and MAC address switching may be signaled 
   separately, or be combined with the PW redundancy signaling defined 
   in [PW-RED], thus when the PE node notifies its PW peer node about 
   its status, it can also carry the MAC address notification and MAC 
   Address Switching messages. 

   When the working PE node (PE-1 in Figure 2) decides to switch its 
   working PW to a standby PW (and the standby PW does not traverse the 
   working PE itself), the working PE node MAY send out a MAC Address 
   Notification message to its backup PE (i.e. PE-2 in Figure 2) with 
   MAC addresses listed in a MAC List TLV and the backup PW identified 
   in the PW-ID TLV, and MAY send out a MAC Address Switching message 
   for the respective working PW for each of the other VPLS peers with 
   MAC addresses in the MAC List TLV and its corresponding backup PW 
   identified in the PW-ID TLV. 

   When the backup PE node triggers PW switching, it MAY send out a MAC 
   Address Switching message for respective backup PW for each of the 
   other VPLS peers with its corresponding working PW in the PW-ID TLV. 

   Under some circumstances, PW endpoints may trigger PW switching in a 
   distributed way, and do the MAC address switching without any 
   signaling message. As no signaling is concerned, this kind of 
   scenario is out of the scope of this document. 

    

6. Processing Rules 

6.1. Receipt of MAC Address Switching Message 

   Upon receipt of the MAC address switching message, the peer PE node 
   SHOULD:  

   - Extract the PW-ID from the message;  

   - Verify that the PW identified by PW-ID and the PW from which the 
     message is received are protecting each other, otherwise MUST 
     ignore this message and MAY log an error locally; 

   - Identify the working PW and the backup PW from these two PWs;  

   - If MAC List TLV is null (absent or empty), then for each MAC 
     addresses in the forwarding table which is associated with the 
     working PW: 
 
 
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      - associate the MAC address with backup PW in the forwarding 
        table 

   - Otherwise, for each MAC address in the MAC List TLV:  

      - associate the MAC address with the backup PW in the forwarding 
        table. 

6.2. Receipt of MAC Address Notification Message 

   When a PE node receives a MAC Address Notification Message, after 
   verification it SHOULD add the MAC addresses carried in the message 
   to its FIB and associate them with the PW identified by the PW-ID 
   TLV carried in the message. 

   Upon receipt of a MAC Address Notification message, the peer node 
   SHOULD: 

   - Extract the PW-ID from the message; 

   - Verify that it is the backup PE for the PE from which this message 
     is received, and the PW identified by PW-ID is a backup PW 
     traverse itself, otherwise MUST ignore this message; 

   - For each MAC address in the MAC List TLV in the received message: 

      - associate the MAC address with the PW identified in the PW-ID 
        TLV in the message and store them in the forwarding table.    

       

7. Applicability 

   This document defines the MAC Address Switching and MAC Address 
   Notification procedures and their application in optimized MAC 
   addresses operation in H-VPLS on topology change. These mechanisms 
   MAY also be used in the scenarios described in [PW-RED]. The use of 
   MAC Address Switching and MAC Address Notification procedures is 
   OPTIONAL. 

    

8. Security Considerations 

   This section is to be enhanced in a future revision of this document.   
   - Control plane aspects     

 
 
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         - LDP security (authentication) methods as described in 
          [RFC5036] are applicable here. Further this document 
          implements security considerations as in [RFC4447] and 
          [RFC4762].  

   - Data plane aspects  

         - This specification does not have any impact on the VPLS      
          forwarding plane. 

   Note that forged switchover messages, such as those defined in this   
   document, represent a significant risk to established PWs and the    
   traffic they carry. If an attack is successful, traffic may be    
   diverted to other destinations which may introduce a denial of 
   service risk (as the traffic may be black-holed or sent on non-
   optimum paths), and may also represent a risk to the confidentiality 
   of the data being transferred. The use of standard LDP security 
   mechanisms, as described above, will mitigate this risk. 
   Additionally, cross-check mechanisms are included in the procedures 
   described in this document to ensure that the switchover of MAC 
   address information is expected. 
      























 
 
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9. IANA Considerations 

9.1. New LDP Message Types 

 
   IANA maintains a registry of LDP code-points at "Label Distribution   
   Protocol (LDP) Name Spaces". There is a sub-registry for LDP message   
   types called "Message Type Name Space". 

   IANA is requested to allocate two new message types from the range    
   0x300-0x3ff. The following values are suggested: 

      Message Name              Type      

      Address Switching         0x0302    

      Address Notification      0x0303    

9.2. New LDP TLV Type 

 
   IANA maintains a registry of LDP code-points at "Label Distribution   
   Protocol (LDP) Name Spaces". There is a sub-registry for LDP TLV 
   type values called "Table, Length, and Value (TLV) Type Name Space". 

   IANA is requested to allocate a new value from the range 0x0000-
   0x3DFF. The following value is suggested: 

   The TLV type of PW-ID is defined as 0x406 and subject to IANA 
   approval. 

    

10. Acknowledgments 

   The authors would like to thank Adrian Farrel and Dan Li for their 
   valuable comments and suggestions. 

   This document was prepared using 2-Word-v2.0.template.dot. 








 
 
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11. References 

11.1. Normative References 

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

   [RFC4447] Martini, L., et al, "Pseudowire Setup and Maintenance 
             Using Label Distribution Protocol (LDP)", RFC 4447, April 
             2006.  

   [RFC4762] Lasserre, M. and Kompella, V., "Virtual Private LAN 
             Services using LDP", RFC 4762, January 2007.   

   [RFC5036] Andersson, L., Minei, I., et al, "LDP Specification", RFC 
             5036, October 2007.    

   [PW-RED]  Muley, P., et al, "Preferential Forwarding Status bit 
             definition", work in progress. 

   [MAC-OPT] Dutta, P., and Lasserre, M., "LDP Extensions for Optimized 
             MAC Address Withdrawal in H-VPLS", work in progress. 

11.2. Informative References 

   [RFC4664] Andersson, L., and Rosen, E., "Framework for Layer 2 
             Virtual Private Networks (L2VPNs)", RFC 4664, September 
             2006.  

      

Author's Addresses 

   Yuanlong Jiang 
   Huawei Technologies Co., Ltd. 
   Bantian industry base, Longgang district 
   Shenzhen, China 
    
   Email: yljiang@huawei.com 
    
   Yang Yang 
   Huawei Technologies Co., Ltd. 
   Bantian industry base, Longgang district 
   Shenzhen, China 
    
   Email: healthinghearts@huawei.com 
    
 
 
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