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      Network Working Group                                       G. Cristallo 
      Internet Draft                                                   Alcatel 
      Document: draft-jacquenet-qos-nlri-05.txt                   C. Jacquenet 
      Category: Experimental                                    France Telecom 
      Expires December 2003                                          June 2003 
                                                                               
       
       
         Providing Quality of Service Indication by the BGP-4 Protocol: the 
                                 QOS_NLRI attribute 
                         <draft-jacquenet-qos-nlri-05.txt> 
       
       
      Status of this Memo 
       
         This document is an Internet-Draft and is in full conformance with 
         all provisions of Section 10 of RFC 2026 [1].  
          
         Internet-Drafts are working documents of the Internet Engineering 
         Task Force (IETF), its areas, and its working groups. Note that other 
         groups may also distribute working documents as Internet-Drafts. 
         Internet-Drafts are draft documents valid for a maximum of six months 
         and may be updated, replaced, or obsoleted by other documents at any 
         time. It is inappropriate to use Internet Drafts as reference 
         material or to cite them other than as "work in progress". 
          
         The list of current Internet-Drafts can be accessed at 
         http://www.ietf.org/ietf/1id-abstracts.txt. 
          
         The list of Internet-Draft Shadow Directories can be accessed at 
         http://www.ietf.org/shadow.html. 
          
         NOTE: a PDF version of this document (which includes the figures 
         mentioned in section 8) can be accessed at http://www.mescal.org. 
          
      Abstract 
          
         This draft specifies an additional BGP4 (Border Gateway Protocol, 
         version 4) attribute, named the "QOS_NLRI" attribute, which aims at 
         propagating QoS (Quality of Service)-related information associated 
         to the NLRI (Network Layer Reachability Information) information 
         conveyed in a BGP UPDATE message. 
          
      Table of Contents 
          
         1.      Conventions Used in this Document..........................2 
         2.      Introduction...............................................2 
         3.      Changes since the Previous Version.........................3 
         4.      Basic Requirements.........................................3 
         5.      The QOS_NLRI Attribute (Type Code tbd*)....................4 
         6.      Operation..................................................7 
       
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         7.      Use of Capabilities Advertisement with BGP-4...............8 
         8.      Simulation Results.........................................9 
         8.1.    A Phased Approach..........................................9 
         8.2.    A Case Study..............................................10 
         8.3.    Additional Results........................................11 
         8.4.    Next Steps................................................12 
         9.      IANA Considerations.......................................13 
         10.     Security Considerations...................................13 
         11.     References................................................13 
         12.     Acknowledgments...........................................14 
         13.     Authors' Addresses........................................14 
         14.     Full Copyright Statement..................................14 
          
          
      1. 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 [2]. 
          
      2. Introduction 
          
         Providing end-to-end quality of service is one of the most important 
         challenges of the Internet, not only because of the massive 
         development of value-added IP service offerings, but also because of 
         the various QoS policies that are currently enforced within an 
         autonomous system, and which may well differ from one AS (Autonomous 
         System) to another. 
          
         For the last decade, value-added IP service offerings have been 
         deployed over the Internet, thus yielding a dramatic development of 
         the specification effort, as far as quality of service in IP networks 
         is concerned. Nevertheless, providing end-to-end quality of service 
         across administrative domains still remains an issue, mainly because: 
          
         - QoS policies may dramatically differ from one service provider to 
           another, 
          
         - The enforcement of a specific QoS policy may also differ from one 
           domain to another, although the definition of a set of common 
           quality of service indicators may be shared between the service 
           providers. 
          
         Activate the BGP4 protocol ([3]) for exchanging reachability 
         information between autonomous systems has been a must for many 
         years. Therefore, disseminating QoS information coupled with 
         reachability information in a given BGP UPDATE message appears to be 
         helpful in enforcing an end-to-end QoS policy. 
          
         This draft aims at specifying a new BGP4 attribute, the QOS_NLRI 
         attribute, which will convey QoS-related information associated to 

       
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         the routes described in the corresponding NLRI field of the 
         attribute. 
          
         This document is organized according to the following sections: 
          
         - Section 3 identifies the changes that have been made in the 
           document since the previous version, 
          
         - Section 4 describes the basic requirements that motivate the 
           approach,  
          
         - Section 5 describes the attribute, 
          
         - Section 6 elaborates on the mode of operation, 
          
         - Section 7 elaborates on the use of the capabilities advertisement 
           feature of the BGP4 protocol, 
          
         - Section 8 depicts the results of an ongoing simulation work, 
          
         - Finally, sections 9 and 10 introduce IANA and some security 
           considerations, respectively. 
          
      3. Changes since the Previous Version  
          
         The current version of this draft reflects the following changes: 
       
         - The format of the attribute has been modified, to include the 
           multiple path advertisement capability, as described in [4], and 
           section 5 has been updated accordingly, 
          
         - Section 6 has been introduced to better depict the mode of 
           operation that now takes into account the multiple path 
           advertisement capability, as described in [4]. From this 
           perspective, this draft can be viewed as an application of this 
           extension, 
          
         - A table of contents has been added, 
          
         - The References section has been updated, 
          
         - Correction of remaining typos. 
           
      4. Basic Requirements 
          
         The choice of using the BGP4 protocol for exchanging QoS information 
         between domains is not only motivated by the fact BGP is currently 
         the only inter-domain (routing) protocol activated in the Internet, 
         but also because the manipulation of attributes is a powerful means 
         for service providers to disseminate QoS information with the desired 
         level of precision.  
          
       
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         The approach presented in this draft has identified the following 
         requirements: 
          
         - Keep the approach scalable. The scalability of the approach can be 
           defined in many ways that include the convergence time taken by the 
           BGP peers to reach a consistent view of the network connectivity, 
           the number of route entries that will have to be maintained by a 
           BGP peer, the dynamics of the route announcement mechanism (e.g., 
           how frequently and under which conditions should an UPDATE message 
           containing QoS information be sent?), etc. 
          
         - Keep the BGP4 protocol operation unchanged. The introduction of a 
           new attribute should not affect the way the protocol operates, but 
           the information contained in this attribute may very well influence 
           the BGP route selection process. 
          
         - Allow for a smooth migration. The use of a specific BGP attribute 
           to convey QoS information should not constrain network operators to 
           migrate the whole installed base at once, but rather help them in 
           gradually deploying the QoS information processing capability. 
       
      5. The QOS_NLRI Attribute (Type Code tbd*) 
                                      
         (*): "tbd" is subject to the IANA considerations section of this 
         draft. 
          
         The QOS_NLRI attribute is an optional transitive attribute that can 
         be used for the following purposes: 
          
         1. To advertise a QoS route to a peer. A QoS route is a route that 
           meets one or a set of QoS requirement(s) to reach a given (set of) 
           destination prefixes. Such QoS requirements can be expressed in 
           terms of minimum one-way delay ([5]) to reach a destination, the 
           experienced delay variation for IP datagrams that are destined to 
           a given destination prefix ([6]), the loss rate experienced along 
           the path to reach a destination, and/or the identification of the 
           traffic that is expected to use this specific route 
           (identification means for such traffic include DSCP (DiffServ Code 
           Point, [7]) marking). These QoS requirements can be used as an 
           input for the BGP route calculation process, 
          
         2. To provide QoS-related information along with the NLRI information 
           in a single BGP UPDATE message. It is assumed that this 
           information will be related to the route (or set of routes) 
           described in the NLRI field of the attribute. 
          
         From a service provider's perspective, the choice of defining the 
         QOS_NLRI attribute as an optional transitive attribute is motivated 
         by the fact that this kind of attribute allows for gradual deployment 
         of the dissemination of QoS-related information by BGP4: not all the 
         BGP peers are supposed to be updated accordingly, while partial 
         deployment of such QoS extensions can already provide an added value, 
       
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         e.g. in the case where a service provider manages multiple domains, 
         and/or has deployed a BGP confederation ([8]). 
          
         This draft makes no specific assumption about the means to actually 
         value this attribute, since this is mostly a matter of 
         implementation, but the reader is suggested to have a look on 
         document [9], as an example of a means to feed the BGP peer with the 
         appropriate information. The QOS_NLRI attribute is encoded as 
         follows: 
          
               +---------------------------------------------------------+ 
               | QoS Information Code (1 octet)                          | 
               +---------------------------------------------------------+ 
               | QoS Information Sub-code (1 octet)                      | 
               +---------------------------------------------------------+ 
               | QoS Information Value (2 octets)                        | 
               +---------------------------------------------------------+ 
               | QoS Information Origin (1 octet)                        | 
               +---------------------------------------------------------+ 
               | Address Family Identifier (2 octets)                    | 
               +---------------------------------------------------------+ 
               | Subsequent Address Family Identifier (1 octet)          | 
               +---------------------------------------------------------+ 
               | Network Address of Next Hop (4 octets)                  | 
               +---------------------------------------------------------+ 
               | Flags (1 octet)                                         | 
               +---------------------------------------------------------+ 
               | Identifier (2 octets)                                   | 
               +---------------------------------------------------------+ 
               | Length (1 octet)                                        | 
               +---------------------------------------------------------+ 
               | Prefix (variable)                                       | 
               +---------------------------------------------------------+ 
          
         The use and meaning of the fields of the QOS_NLRI attribute are 
         defined as follows: 
          
         -  QoS Information Code: 
          
             This field carries the type of the QOS information. The following 
             types have been identified so far: 
          
         (0) Reserved 
         (1) Packet rate, i.e. the number of IP datagrams that can be 
             transmitted (or have been lost) per unit of time, this number 
             being characterized by the elaboration provided in the QoS 
             Information Sub-code (see below)  
         (2) One-way delay metric  
         (3) Inter-packet delay variation  
         (4) PHB Identifier  
          
          
       
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         -  QoS Information Sub-Code: 
          
             This field carries the sub-type of the QoS information. The 
             following sub-types have been identified so far: 
          
         (0) None (i.e. no sub-type, or sub-type unavailable, or unknown sub-
             type) 
         (1) Reserved rate 
         (2) Available rate 
         (3) Loss rate 
         (4) Minimum one-way delay 
         (5) Maximum one-way delay 
         (6) Average one-way delay 
          
         The instantiation of this sub-code field MUST be compatible with the 
         value conveyed in the QoS Information code field, as stated in the 
         following table (the rows represent the QoS Information Code possible 
         values, the columns represent the QoS Information Sub-code values 
         identified so far, while the "X" sign indicates incompatibility). 
                   
                  +---------------------------------------+ 
                  |    |  0 |  1 |  2 |  3 |  4 |  5 |  6 | 
                  +---------------------------------------+ 
                  |  0 |    |    |    |    |    |    |    | 
                  +---------------------------------------+ 
                  |  1 |    |    |    |    |  X |  X |  X | 
                  +---------------------------------------+ 
                  |  2 |    |  X |  X |  X |    |    |    | 
                  +---------------------------------------+ 
                  |  3 |    |  X |  X |  X |  X |  X |  X | 
                  +---------------------------------------+ 
                  |  4 |    |  X |  X |  X |  X |  X |  X | 
                  +---------------------------------------+ 
          
         -  QoS Information Value: 
          
             This field indicates the value of the QoS information. The 
             corresponding units obviously depend on the instantiation of the 
             QoS Information Code. Namely, if: 
          
         (a) QoS Information Code field is "0", no unit specified, 
         (b) QoS Information Code field is "1", unit is kilobits per second 
             (kbps), and the rate encoding rule is composed of a 3-bit 
             exponent (with an assumed base of 8) followed by a 13-bit 
             mantissa, as depicted in the figure below: 
                                   0      8       16 
                                   |       |       | 
                                   ----------------- 
                                   |Exp| Mantissa  | 
                                   ----------------- 
       
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             This encoding scheme advertises a numeric value that is (2^16 -1 
             - exponential encoding of the considered rate), as depicted in 
             [10]. 
         (c) QoS Information Code field is "2", unit is milliseconds, 
         (d) QoS Information Code field is "3", unit is milliseconds, 
         (e) QoS Information Code field is "4", no unit specified. 
          
         -  QoS Information Origin: 
          
             This field provides indication on the origin of the path 
             information, as defined in section 4.3.of [3].  
          
         -  Address Family Identifier (AFI): 
          
             This field carries the identity of the Network Layer protocol 
             associated with the Network Address that follows. Currently 
             defined values for this field are specified in [11] (see the 
             Address Family Numbers section of this reference document). 
          
         -  Subsequent Address Family Identifier (SAFI): 
          
             This field provides additional information about the type of the 
             prefix carried in the QOS_NLRI attribute. 
          
         -  Network Address of Next Hop: 
          
             This field contains the IPv4 Network Address of the next router 
             on the path to the destination prefix, (reasonably) assuming that 
             such routers can at least be addressed according to the IPv4 
             formalism. 
          
         -  Flags, Identifier, Length and Prefix fields: 
          
             These four fields actually compose the NLRI field of the QOS_NLRI 
             attribute, and their respective meanings are as defined in 
             section 2.2.2 of [4].   
          
      6. Operation 
          
         When advertising a QOS_NLRI attribute to an external peer, a router 
         may use one of its own interface addresses in the next hop component 
         of the attribute, given the external peer to which one or several 
         route(s) is (are) being advertised shares a common subnet with the 
         next hop address.  This is known as a "first party" next hop 
         information. 
          
         A BGP speaker can advertise to an external peer an interface of any 
         internal peer router in the next hop component, provided the external 
         peer to which the route is being advertised shares a common subnet 
         with the next hop address.  This is known as a "third party" next hop 
         information. 
       
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         A BGP speaker that sends an UPDATE message with the QOS_NLRI 
         attribute has the ability to advertise multiple QoS routes, since the 
         Identifier field of the attribute is part of the NLRI description. In 
         particular, the same prefix can be advertised more than once without 
         subsequent advertisements that would replace previous announcements. 
          
         Since the resolution of the NEXT_HOP address that is always conveyed 
         in a BGP UPDATE message is left to the responsibility of the IGP that 
         has been activated within the domain, the best path according to the 
         BGP route selection process depicted in [3] SHOULD also be 
         advertised. As long as the routers on the path towards the address 
         depicted in the NEXT_HOP attribute of the message have the additional 
         paths depicted in the QOS_NLRI attribute, the propagation of QoS 
         routes within a domain where all the routers are QOS_NLRI aware 
         should not yield inconsistent routing. 
          
         A BGP UPDATE message that carries the QOS_NLRI MUST also carry the 
         ORIGIN and the AS_PATH attributes (both in eBGP and in iBGP 
         exchanges). Moreover, in iBGP exchanges such a message MUST also 
         carry the LOCAL_PREF attribute. If such a message is received from an 
         external peer, the local system shall check whether the leftmost AS 
         in the AS_PATH attribute is equal to the autonomous system number of 
         the peer than sent the message. If that is not the case, the local 
         system shall send the NOTIFICATION message with Error Code UPDATE 
         Message Error, and the Error Sub-code set to Malformed AS_PATH. 
          
         Finally, an UPDATE message that carries no NLRI, other than the one 
         encoded in the QOS_NLRI attribute, should not carry the NEXT_HOP 
         attribute. If such a message contains the NEXT_HOP attribute, the BGP 
         speaker that receives the message should ignore this attribute. 
          
      7. Use of Capabilities Advertisement with BGP-4 
          
         A BGP speaker that uses the QOS_NLRI attribute SHOULD use the 
         Capabilities Advertisement procedures, as defined in [12], so that it 
         might be able to determine if it can use such an attribute with a 
         particular peer. 
          
         The fields in the Capabilities Optional Parameter are defined as 
         follows: 
          
         -  The Capability Code field is set to N (127 < N < 256, when 
             considering the "Private Use" range, as specified in [13]), while 
             the Capability Length field is set to "1". 
          
         -  The Capability Value field is a one-octet field, which contains 
             the Type Code of the QOS_NLRI attribute, as defined in the 
             introduction of section 5 of the present draft. 
          
         In addition, the multiple path advertisement capability MUST be 
         supported, as defined in section 2.1 of [4]. 
       
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      8. Simulation Results  
          
      8.1. A Phased Approach 
          
         The simulation work basically aims at qualifying the scalability of 
         the usage of the QOS_NLRI attribute for propagating QoS-related 
         information across domains.  
          
         This effort also focused on the impact on the stability of the BGP 
         routes, by defining a set of basic engineering rules for the 
         introduction of additional QoS information, as well as design 
         considerations for the computation and the selection of "QoS routes". 
          
         This ongoing development effort is organized into a step-by-step 
         approach, which consists in the following phases: 
          
           1. Model an IP network composed of several autonomous systems. 
              Since this simulation effort is primarily focused on the 
              qualification of the scalability related to the use of the 
              QOS_NLRI attribute for exchanging QoS-related information 
              between domains, it has been decided that the internal 
              architecture of such domains should be kept very simple, i.e. 
              without any specific IGP interaction, 
          
           2. Within this IP network, there are BGP peers that are QOS_NLRI 
              aware, i.e. they have the ability to process the information 
              conveyed in the attribute, while the other routers are not: the 
              latter do not recognize the QOS_NLRI attribute by definition, 
              and they will forward the information to other peers, by setting 
              the Partial bit in the attribute, meaning that the information 
              conveyed in the message is incomplete. This approach contributes 
              to the qualification of a progressive deployment of QOS_NLRI-
              aware BGP peers, 
          
           3. As far as QOS_NLRI aware BGP peers are concerned, they will 
              process the information contained in the QOS_NLRI attribute to 
              possibly influence the route decision process, thus yielding the 
              selection (and the announcement) of distinct routes towards a 
              same destination prefix, depending on the QoS-related 
              information conveyed in the QOS_NLRI attribute,  
          
           4. Modify the BGP route decision process: at this stage of the 
              simulation, the modified decision process relies upon the one-
              way delay information (which corresponds to the QoS Information 
              Code field of the attribute valued at "2"), and it also takes 
              into account the value of the Partial bit of the attribute. 
          
         Once the creation of these components of the IP network has been 
         completed (together with the modification of the BGP route selection 
         process), the behavior of a QOS_NLRI-capable BGP peer is as follows.  
       
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         Upon receipt of a BGP UPDATE message that contains the QOS_NLRI 
         attribute, the router will first check if the corresponding route is 
         already stored in its local RIB, according to the value of the one-
         way delay information contained in both QoS Information Code and Sub-
         code fields of the attribute.  
          
         If not, the BGP peer will install the route in its local RIB. 
         Otherwise (i.e. an equivalent route already exists in its database), 
         the BGP peer will select the best of both routes according to the 
         following criteria: 
          
         - If both routes are said to be either incomplete (Partial bit has 
            been set) or complete (Partial bit is unset), the route with the 
            lowest delay will be selected, 
          
         - Otherwise, a route with the Partial bit unset is always preferred 
            over any other route, even if this route reflects a higher transit 
            delay. 
          
         If ever both Partial bit and transit delay information are not 
         sufficient to make a decision, the standard BGP decision process 
         (according to the breaking ties mechanism depicted in [3]) is 
         performed. 
          
      8.2. A Case Study 
          
         As stated in the previous section 8.1, the current status of the 
         simulation work basically relies upon the one-way transit delay 
         information only, as well as the complete/incomplete indication of 
         the Partial bit conveyed in the QOS_NLRI attribute. 
          
         The following figures depict the actual processing of the QoS-related 
         information conveyed in the QOS_NLRI attribute, depending on whether 
         the peer is QOS_NRLI-aware or not. 
       
                                [Fig. 1: A Case Study.] 
          
         Figure 1 depicts the IP network that has been modelled, while figure 
         2 depicts the propagation of a BGP UPDATE message that contains the 
         QOS_NLRI attribute, in the case where the contents of the attribute 
         are changed, because of complete/incomplete conditions depicted by 
         the Partial bit of the QOS_NLRI attribute. 
          
             [Fig. 2: Propagation of One-way Delay Information via BGP4.] 
          
         Router S in figure 2 is a QOS_NRLI-capable speaker. It takes 20 
         milliseconds for node S to reach network 192.0.20.0: this information 
         will be conveyed in a QOS_NLRI attribute that will be sent by node S 
         in a BGP UPDATE message with the Partial bit of the QOS_NLRI 
         attribute unset.  
          
       
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         Router A is another QOS_NLRI BGP peer, and it takes 3 milliseconds 
         for A to reach router S. Node A will update the QoS-related 
         information of a QOS_NLRI attribute, indicating that, to reach 
         network 192.0.20.0, it takes 23 milliseconds. Router A will install 
         this new route in its database, and will propagate the corresponding 
         UPDATE message to its peers. 
          
         On the other hand, router B is not capable of processing the 
         information conveyed in the QOS_NLRI attribute, and it will therefore 
         set the Partial bit of the QOS_NLRI attribute in the corresponding 
         UPDATE message, leaving the one-way delay information detailed in 
         both QoS Information Code and Sub-code unchanged.  
          
         Upon receipt of the UPDATE message sent by router A, router E will 
         update the one-way delay information since it is a QOS_NRLI-capable 
         peer. Finally, router D receives the UPDATE message, and selects a 
         route  with  a  40  milliseconds  one-way  delay  to  reach  network 
         192.0.20.0, as depicted in figure 3. 
          
                    [Fig. 3: Selecting QoS Routes Across Domains.] 
          
         This simulation result shows that the selection of a delay-inferred 
         route over a BGP route may not yield an optimal decision. In the 
         above example, the 40 ms-route goes through routers D-E-A-S, while a 
         "truly optimal" BGP route would be through routers D-E-F-A-S, hence a 
         38 ms-route. This is because of a BGP4 rule that does not allow 
         router F to send an UPDATE message towards router E, because router F 
         received the UPDATE message from router A thanks to the iBGP 
         connection it has established with A.  
          
      8.3. Additional Results 
          
         The following table reflects the results obtained from a simulation 
         network composed of 9 autonomous systems and 20 BGP peers. The 
         numbers contained in the columns reflect the percentage of serviced 
         requirements, where the requirements are expressed in terms of delay. 
          
         Three parameters have been taken into account: 
          
         - The percentage of BGP peers that have the ability to process the 
           information conveyed in the QOS_NLRI attribute (denoted as "x% Q-
           BGP" in the following table), 
          
         - The transit delays "observed" (and artificially simulated) on each 
           transmission link: the higher the delays, the lower the percentage 
           of serviced QoS requirements, 
          
         - The QoS requirements themselves, expressed in terms of delay: as 
           such, the strongest requirements (i.e. the lowest delays) have less 
           chance to be satisfied. 
          
                   
       
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                  +-------------------------------------------+ 
                  | Delay | 0% Q-BGP | 50% Q-BGP | 100% Q-BGP | 
                  +-------------------------------------------+ 
                  |  3    |    11    |    8,3    |    11      | 
                  +-------------------------------------------+ 
                  |  5    |    30,5  |    30,5   |    36,1    | 
                  +-------------------------------------------+ 
                  |  6    |    40    |    47,2   |    55,5    | 
                  +-------------------------------------------+ 
                  |  7    |    47    |    59,7   |    72,2    | 
                  +-------------------------------------------+ 
                  |  8    |    62,5  |    79     |    91,6    | 
                  +-------------------------------------------+       
                  |  9    |    63    |    84,7   |    97,2    | 
                  +-------------------------------------------+       
                  |  10   |    70,8  |    90,2   |    98,6    | 
                  +-------------------------------------------+       
                  |  11   |    76,3  |    93     |    98,6    | 
                  +-------------------------------------------+ 
                  |  12   |    86,1  |    97,2   |    100     | 
                  +-------------------------------------------+ 
                  |  13   |    88,8  |    98,6   |    100     | 
                  +-------------------------------------------+ 
                  |  14   |    94,4  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  15   |    94,4  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  16   |    94,4  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  17   |    97,2  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  18   |    98,6  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  19   |    98,6  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  20   |    98,6  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  21   |    98,6  |    100    |    100     | 
                  +-------------------------------------------+ 
                  |  22   |    100   |    100    |    100     | 
                  +-------------------------------------------+ 
          
         This table clearly demonstrates the technical feasibility of the 
         approach, and how the use of the QOS_NLRI attribute can improve the 
         percentage of serviced QoS requirements. 
          
      8.4. Next Steps 
          
         The above-mentioned simulation effort is currently pursued in order 
         to better qualify the interest of using the BGP4 protocol to convey 
         QoS-related information between domains, from a scalability 

       
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         perspective, i.e. the growth of BGP traffic vs. the stability of the 
         network.  
          
         The stability of the IP network is probably one of the most important 
         aspects, since QoS-related information is subject to very dynamic 
         changes, thus yielding non-negligible risks of flapping. 
          
      9. IANA Considerations  
          
         Section 5 of this draft documents an optional transitive BGP-4 
         attribute named "QOS_NLRI" whose type value will be assigned by IANA. 
         Section 6 of this draft also documents a Capability Code whose value 
         should be assigned by IANA as well. 
                                                
      10. Security Considerations 
          
         This additional BGP-4 attribute specification does not change the 
         underlying security issues inherent in the existing BGP-4 protocol 
         specification [14]. 
               
      11. References 
                 
         [1]  Bradner, S., "The Internet Standards Process -- Revision 3", 
               BCP 9, RFC 2026, October 1996. 
         [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement 
               Levels", BCP 14, RFC 2119, March 1997. 
         [3]  Rekhter Y., Li T., "A Border Gateway Protocol 4 (BGP-4)", RFC 
               1771, March 1995. 
         [4]  Walton, D., et al., "Advertisement of Multiple Paths in BGP", 
               draft-walton-bgp-add-paths-01.txt, Work in Progress, November 
               2002. 
         [5]  Almes, G., Kalidindi, S., "A One-Way-Delay Metric for IPPM", 
               RFC 2679, September 1999. 
         [6]  Demichelis, C., Chimento, P., "IP Packet Delay Variation Metric 
               for IP Performance Metrics (IPPM)", RFC 3393, November 2002. 
         [7]  Nichols, K., Blake, S., Baker, F., Black, D., "Definition of 
               the Differentiated Services Field (DS Field) in the IPv4 and 
               IPv6 Headers", RFC 2474, December 1998. 
         [8]  Traina, P., McPherson, D., Scudder, J., " Autonomous System 
               Confederations for BGP", RFC 3065, February 2001. 
         [9]  Jacquenet, C., "A COPS client-type for IP traffic engineering", 
               draft-jacquenet-ip-te-cops-04.txt, Work in Progress, January 
               2003. 
         [10] Apostolopoulos, G. et al, "QoS Routing Mechanisms and OSPF 
               Extensions", RFC 2676, August 1999. 
         [11] Reynolds, J., Postel, J., "ASSIGNED NUMBERS", RFC 1700, October 
               1994. 
         [12] Chandra, R., Scudder, J., "Capabilities Advertisement with BGP-
               4", RFC 3392, November 2002. 
       


       
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         [13] Narten, T., Alvestrand, H., "Guidelines for Writing an IANA 
               Considerations Section in RFCs", RFC 2434, October 1998. 
         [14] Heffernan, A., "Protection of BGP sessions via the TCP MD5 
               Signature Option", RFC 2385, August 1998. 
          
      12. Acknowledgments 
                               
         Part of this work is funded by the European Commission, within the 
         context of the MESCAL (Management of End-to-End Quality of Service 
         Across the Internet At Large, http://www.mescal.org) project, which 
         is itself part of the IST (Information Society Technologies) research 
         program. 
          
         The author would also like to thank all the partners of the MESCAL 
         project for the fruitful discussions that have been conducted within 
         the context of the traffic engineering specification effort of the 
         project, as well as O. Bonaventure and B. Carpenter for their 
         valuable input. 
          
      13. Authors' Addresses 
          
         Geoffrey Cristallo 
         Alcatel 
         Francis Wellesplein, 1 
         2018 Antwerp 
         Belgium 
         Phone: +32 (0)3 240 7890 
         E-Mail: geoffrey.cristallo@alcatel.be 
          
         Christian Jacquenet 
         France Telecom  
         3, avenue Fran‡ois Ch‚teau 
         CS 36901 
         35069 Rennes Cedex 
         France 
         Phone: +33 2 99 87 63 31 
         Email: christian.jacquenet@francetelecom.com 
          
      14. Full Copyright Statement 
       
         Copyright(C) The Internet Society (2003). All Rights Reserved. 
          
         This document and translations of it may be copied and furnished to 
         others, and derivative works that comment on or otherwise explain it 
         or assist its implementation may be prepared, copied, published and 
         distributed, in whole or in part, without restriction of any kind, 
         provided that the above copyright notice and this paragraph are 
         included on all such copies and derivative works. However, this 
         document itself may not be modified in any way, such as by removing 
         the copyright notice or references to the Internet Society or other 
         Internet organizations, except as needed for the purpose of 
       
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         developing Internet standards in which case the procedures for 
         copyrights defined in the Internet Standards process must be 
         followed, or as required to translate it into languages other than 
         English.  
          
         The limited permissions granted above are perpetual and will not be 
         revoked by the Internet Society or its successors or assigns.  
          
         This document and the information contained herein is provided on an 
         "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 
         TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 
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         MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 
          
          



































       
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