MPLS协议及其QoS仿真
摘要
Internet在近些年中以惊人的速度增长，网络的应用范围也越来越广，人们已不满足目前IP网络所提供的E-Mail、上网等服务，还希望能够得到诸如宽带、多媒体、QoS等多种业务，这对Internet服务提供商(ISP)提出了新的挑战。九十年代，ATM曾经是被普遍看好的能够提供多种业务的交换技术，但是由于实际的网络中人们越来越普遍的采用IP技术，纯ATM网络已经不可能，现有ATM的使用一般也都支持IP业务。因此人们就希望IP也能提供ATM一样多种类型的服务。MPLS (Multiprotocol Label Switch，多协议标签交换)就是在这种背景下产生的一种技术，而且越来越被运营商看好，成为在IP网络运营商提供增值业务的手段。MPLS是“多协议标记交换”(Multiprotocol Label Switching)的缩写。它是一种根据“带路由信息”的标记进行分组交换的新型网络通信技术，结合了交换技术和路由技术的诸多特点。MPLS将ATM中的流量工程引入了分组交换网中，而且它并不被限定在某一种二层协议上，能够运行在多种传输媒介上(ATM，帧中继，以太网)，具有很强的适应性。
我们知道，现在的网络是一个尽力而为的服务模型，在这种网络服务模型中，网络为所有用户提供尽力而为的服务和带宽，而不是按照预约的速度和服务级别提供服务。当网络拥塞发生时，它也不能根据不同的服务级别提供有区别的对待和QoS保证。鉴于此，许多支持QoS的协议机制被提出，如基于单个(或一类)流量的直接QoS机制——集成服务(InteServ)和区分服务(DiffServ)，以及从宏观上实现整个网络的QoS优化的流量工程(TE)。集成服务是基于控制信令的，需要保持控制状态，实现相对复杂。而区分服务则为网络提供了一个提供有“区别”服务的服务模型，在网络入口处对分组进行标记、整形，域内核心节点只需根据PHB提供不同级别的服务，不用保存各通信流的状态信息，这样大大提高了网络的可扩展性。而流量工程实际上是一种间接的QoS实现技术，它致力于对整个网络资源的最优利用，从而改善网络的性能。
实践表明，DiffServ是一种可扩展性很强的组网方法，而MPLS可以快速进行分组交换并能很好的支持流量工程。如果将两种技术有机的结合起来，从而为整个网络提供QoS保证，对骨干网络提供商来说将是一个非常具有吸引力的组网策略。事实上，从技术层面上来说，多协议标签交换MPLS可以很好地支持包括流量工程和直接QoS在内的QoS机制，DiffServ自然也不例外，这无疑增强
MpLs协议及其QoS仿真
了我们将这两种技术结合在一起的信心。遗憾的是，目前用于网络协议模拟的主
要平台之一的ns中，虽然对MPLS有所支持，但由于版本较早(当时MPLS还
未最终标准化)，未按协议标准实现，更没有实现对Diffsery的支持(根据Diffsery
的需要对LDP进行了扩展是后来提出的)。在ns中实现基于标准MPLS协议的
仿真实现功能和对区分服务提供直接的支持，正是我们所主要关注的。
本文中，我们对MPLs的基本协议，体系结构以及它的QoS机制做了回顾。
然后，设计并实现了一个基于NS的MPLS模拟环境，它支持基本的MPLS功能
(如LDP，标记交换，LSP的建立等)。接着，我们在基本MPLS协议的基础上，
实现了基于Di邢ery的QoS保证。为了验证我们实验的正确性，文章的最后，
我们做了两个实验，一个是对基本MPLS信令的验证，一个是对Di邢ery的验证。
The Internet is growing at an amazing speed in recent years,it ISPs are challenged with rapidly improved network and new multi services. (Email,web surf,broad band , multimedia ,QoS etc) In 90's, ATM proved super excellent solution for performance and raffle engineering to ISP.And many carriers found it is very economical to implement Internet multi-service in ATM network.But ip-based network is becoming more prevalent each year, pure ATM based network is impossible in reality.In fact , today 's ATM network is used to carry IP based traffic.So people wish to combine IP traffic and ATM function in one network technology. MPLS progressed in the background. MPLS stands for "Multiprotocol Label Switching",it integrates the label-swapping paradigm with network-layer routingjt brings the TE(traffic engineering) of ATM to packet-based network and also it can run over nearly any transport medium (ATM, FR, Ethernet...) instead of being tired to a specific layer-2 encapsulation.
As we know,the current default Internet assumes the "best-effort" service model .In this model the network allocates bandwidth among all of users at best it can and attempts to serve all of them without making any explicit commitement as to rate or any other service When congestion occurs.it can't provide QoS guarantee for different service classes. So many QoS mechanism was brought forward ,such as one traffic (or one class) based QoS technology-InteServ DiffServ ,and macrocosmic QoS guarantee -TE. RSVP is based on control signal which need save state information , it is more difficult than DiffServ. In Differentiated Service , it define a model for implementing scalable differentiation of QoS in the Internet .Packets are classified and marked,policed and shaped at edge of the network in order to receive a particular per-hop forwarding behaviour on nodes along their path.Per-flow state does not need to be maintained in the interior network nodes,thus leading to increased scalability.TE is the process of controlling how traffic flows through one's network so as to optimize resource utilization and network performance,in point of fact TE is a indirect QoS mechanism.
Differentiated Servic(DiffServ) is scalable for deployment in today's Internet ,
and Multiprotocol Lable Switching(MPLS) provides fast packet switching and the opportunity for traffic engineering.Thus,the combination of DiffServ and MPLS presents a very attractive strategy to backbone network providers.In fact ,MPLS is good at implementing QoS,such Diffserv,RSP and TE. This strengthen our confidence in its success.But, to our disappointment,it hasn't been implemented in ns,which is one of the most prevalent network simulator.To implement standard mpls fuction and diffserv in mpls are our major attention.
In this paper,we will review the features , main components of MPLS and its QoS mechanism (such as InterServ,DiffServ,TE).And then we will describe the design and the implementation of MPLS Network Simulator,which supports the establishment of LSP as well as any other basic MPLS functions such as LDP and Label switching and various approaches which can be used to support differentiated services in MPLS environment and implement DiffServ+MPLS in ns.
To verify the accuracy and efficiency of our implementation,two examples are simulated and evaluated.One is a simulation for basic MPLS functions .The other is a simulation for traffics with different QoS each other in MPLS network.
我们知道，现在的网络是一个尽力而为的服务模型，在这种网络服务模型中，网络为所有用户提供尽力而为的服务和带宽，而不是按照预约的速度和服务级别提供服务。当网络拥塞发生时，它也不能根据不同的服务级别提供有区别的对待和QoS保证。鉴于此，许多支持QoS的协议机制被提出，如基于单个(或一类)流量的直接QoS机制——集成服务(InteServ)和区分服务(DiffServ)，以及从宏观上实现整个网络的QoS优化的流量工程(TE)。集成服务是基于控制信令的，需要保持控制状态，实现相对复杂。而区分服务则为网络提供了一个提供有“区别”服务的服务模型，在网络入口处对分组进行标记、整形，域内核心节点只需根据PHB提供不同级别的服务，不用保存各通信流的状态信息，这样大大提高了网络的可扩展性。而流量工程实际上是一种间接的QoS实现技术，它致力于对整个网络资源的最优利用，从而改善网络的性能。
实践表明，DiffServ是一种可扩展性很强的组网方法，而MPLS可以快速进行分组交换并能很好的支持流量工程。如果将两种技术有机的结合起来，从而为整个网络提供QoS保证，对骨干网络提供商来说将是一个非常具有吸引力的组网策略。事实上，从技术层面上来说，多协议标签交换MPLS可以很好地支持包括流量工程和直接QoS在内的QoS机制，DiffServ自然也不例外，这无疑增强
MpLs协议及其QoS仿真
了我们将这两种技术结合在一起的信心。遗憾的是，目前用于网络协议模拟的主
要平台之一的ns中，虽然对MPLS有所支持，但由于版本较早(当时MPLS还
未最终标准化)，未按协议标准实现，更没有实现对Diffsery的支持(根据Diffsery
的需要对LDP进行了扩展是后来提出的)。在ns中实现基于标准MPLS协议的
仿真实现功能和对区分服务提供直接的支持，正是我们所主要关注的。
本文中，我们对MPLs的基本协议，体系结构以及它的QoS机制做了回顾。
然后，设计并实现了一个基于NS的MPLS模拟环境，它支持基本的MPLS功能
(如LDP，标记交换，LSP的建立等)。接着，我们在基本MPLS协议的基础上，
实现了基于Di邢ery的QoS保证。为了验证我们实验的正确性，文章的最后，
我们做了两个实验，一个是对基本MPLS信令的验证，一个是对Di邢ery的验证。
The Internet is growing at an amazing speed in recent years,it ISPs are challenged with rapidly improved network and new multi services. (Email,web surf,broad band , multimedia ,QoS etc) In 90's, ATM proved super excellent solution for performance and raffle engineering to ISP.And many carriers found it is very economical to implement Internet multi-service in ATM network.But ip-based network is becoming more prevalent each year, pure ATM based network is impossible in reality.In fact , today 's ATM network is used to carry IP based traffic.So people wish to combine IP traffic and ATM function in one network technology. MPLS progressed in the background. MPLS stands for "Multiprotocol Label Switching",it integrates the label-swapping paradigm with network-layer routingjt brings the TE(traffic engineering) of ATM to packet-based network and also it can run over nearly any transport medium (ATM, FR, Ethernet...) instead of being tired to a specific layer-2 encapsulation.
As we know,the current default Internet assumes the "best-effort" service model .In this model the network allocates bandwidth among all of users at best it can and attempts to serve all of them without making any explicit commitement as to rate or any other service When congestion occurs.it can't provide QoS guarantee for different service classes. So many QoS mechanism was brought forward ,such as one traffic (or one class) based QoS technology-InteServ DiffServ ,and macrocosmic QoS guarantee -TE. RSVP is based on control signal which need save state information , it is more difficult than DiffServ. In Differentiated Service , it define a model for implementing scalable differentiation of QoS in the Internet .Packets are classified and marked,policed and shaped at edge of the network in order to receive a particular per-hop forwarding behaviour on nodes along their path.Per-flow state does not need to be maintained in the interior network nodes,thus leading to increased scalability.TE is the process of controlling how traffic flows through one's network so as to optimize resource utilization and network performance,in point of fact TE is a indirect QoS mechanism.
Differentiated Servic(DiffServ) is scalable for deployment in today's Internet ,
and Multiprotocol Lable Switching(MPLS) provides fast packet switching and the opportunity for traffic engineering.Thus,the combination of DiffServ and MPLS presents a very attractive strategy to backbone network providers.In fact ,MPLS is good at implementing QoS,such Diffserv,RSP and TE. This strengthen our confidence in its success.But, to our disappointment,it hasn't been implemented in ns,which is one of the most prevalent network simulator.To implement standard mpls fuction and diffserv in mpls are our major attention.
In this paper,we will review the features , main components of MPLS and its QoS mechanism (such as InterServ,DiffServ,TE).And then we will describe the design and the implementation of MPLS Network Simulator,which supports the establishment of LSP as well as any other basic MPLS functions such as LDP and Label switching and various approaches which can be used to support differentiated services in MPLS environment and implement DiffServ+MPLS in ns.
To verify the accuracy and efficiency of our implementation,two examples are simulated and evaluated.One is a simulation for basic MPLS functions .The other is a simulation for traffics with different QoS each other in MPLS network.
引文
Rekhter K, Swallow G, Farinacci D, Katz D. Tag Switching Architecture Overview, Proceeding of The IEEE,Vol85,No 12, Dec 1997: 1973-1983
Paul Boustead, Scott Barnett, Joe Chicharo, Gary Anido," Label Switching and IP Version 6",1998 IEEE
Y. Rekhter, B. Davie, E. Rosen, G. Swallow, Cisco Systems, Inc., " Cisco Systems' Tag Switching
Architecture Overview", RFC 2105,February 1997
E. Rosen,A. Viswanathan and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001
.Ash, Y. Lee, P. Ashwood-Smith, B. Jamoussi, D. Fedyk," LSP Modification Using CR-LDP", RFC 3214, January 2002
Stardust.com,Inc ,"White Paper-The Need for QoS",July 1999
Stardust.com,Inc,"White Paper-Introduction to QoS Policies",July 6,1999
K. Nichols, V. Jacobson, L. Zhang,"A Two-bit Differentiated Services Architecture for the Internet",RFC 2638,July 1999
.Heinanen, R. Guerin, "A Single Rate Three Color Marker", RFC 2697, September 1999
V. Jacobson, K. Nichols, K. Poduri,"An Expedited Forwarding PHB", RFC 2598, June 1999
Azeem Feroz, Shivkumar Kalyanaraman,Amit Rao, "A TCP-Friendly Traffic Marker for IP Differentiated Services"
K. Nichols , S. Blake, F. Baker, D. Black, "Definition of the Differentiated Service Field(DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998
David D. Clark, Wenjia Fang, "Explicit Allocation of Best-Effort Packet Delivery Service", IEEE/ACM TRANSACTIONS ON NETWORKING, August 1998
E. Rosen, Y. Rekhter, "BGP/MPLS VPNS",RFC 2547, March 1999
Chuck Semeria, Juniper Networks, "RFC 2547bis: BGP/MPLS VPN Fundamentals", 2001
Hiroyuk Saito, Yasuhiro Miyao, an Makiko Yoshida, "Traffic Engineering using Multipls Multipoint-to-Point LSPs",IEEE Infocom, 2000
Xipeng Xiao, Alan Hannan, Brook Bailey, and Lionel M.Ni, "Traffic Engineering with MPLS in the internet"
Aolghasem Asgari,Steven Van den Berghe, Christian Jacquenet,etc,"A Monitoring and Measurement Architecture for Traffic Engineered IP Networks"
Deering. "Host Extensions for IP Multicasting," RFC-1112, August 1, 1989
Christian Hutiema著，陶文星译，“因特网路由技术，清华大学出版社，1998．4
D. Ooms. Sales, W. Livens, A. Acharya, F. Griffoul. F. Ansari, "Framework for IP Multicast in MPLS", IETF Draft, April 2002
Arup Aeharya, Frederic Griffoul, Furquan Ansari,"IP Multicast Support in MPLS"
Ali Boudani, Jean-Marie Bonnin, "An Effective Solution for Multicast Scalability",IETF Draft, June 2002
Baijian Yang, Prasant Mohapatra,"EDGE ROUTER MULTICASTING WITH MPLS TRAFFIC ENGINNEERING"
Miercom, "Cisco MPLS based VPNS: Equivalent to the security of Frame Relay and ATM", March 30, 2001
Floyd, S. and V. Jacobason,"Random Early Detection Gateways for Congestion Avoidance.", 1993.
Clark, D. and W. Fang,"Explicit Allocation of Best Effort Packet Deliver Service.
Paul Boustead, Scott Barnett, Joe Chicharo, Gary Anido," Label Switching and IP Version 6",1998 IEEE
Y. Rekhter, B. Davie, E. Rosen, G. Swallow, Cisco Systems, Inc., " Cisco Systems' Tag Switching
Architecture Overview", RFC 2105,February 1997
E. Rosen,A. Viswanathan and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001
.Ash, Y. Lee, P. Ashwood-Smith, B. Jamoussi, D. Fedyk," LSP Modification Using CR-LDP", RFC 3214, January 2002
Stardust.com,Inc ,"White Paper-The Need for QoS",July 1999
Stardust.com,Inc,"White Paper-Introduction to QoS Policies",July 6,1999
K. Nichols, V. Jacobson, L. Zhang,"A Two-bit Differentiated Services Architecture for the Internet",RFC 2638,July 1999
.Heinanen, R. Guerin, "A Single Rate Three Color Marker", RFC 2697, September 1999
V. Jacobson, K. Nichols, K. Poduri,"An Expedited Forwarding PHB", RFC 2598, June 1999
Azeem Feroz, Shivkumar Kalyanaraman,Amit Rao, "A TCP-Friendly Traffic Marker for IP Differentiated Services"
K. Nichols , S. Blake, F. Baker, D. Black, "Definition of the Differentiated Service Field(DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998
David D. Clark, Wenjia Fang, "Explicit Allocation of Best-Effort Packet Delivery Service", IEEE/ACM TRANSACTIONS ON NETWORKING, August 1998
E. Rosen, Y. Rekhter, "BGP/MPLS VPNS",RFC 2547, March 1999
Chuck Semeria, Juniper Networks, "RFC 2547bis: BGP/MPLS VPN Fundamentals", 2001
Hiroyuk Saito, Yasuhiro Miyao, an Makiko Yoshida, "Traffic Engineering using Multipls Multipoint-to-Point LSPs",IEEE Infocom, 2000
Xipeng Xiao, Alan Hannan, Brook Bailey, and Lionel M.Ni, "Traffic Engineering with MPLS in the internet"
Aolghasem Asgari,Steven Van den Berghe, Christian Jacquenet,etc,"A Monitoring and Measurement Architecture for Traffic Engineered IP Networks"
Deering. "Host Extensions for IP Multicasting," RFC-1112, August 1, 1989
Christian Hutiema著，陶文星译，“因特网路由技术，清华大学出版社，1998．4
D. Ooms. Sales, W. Livens, A. Acharya, F. Griffoul. F. Ansari, "Framework for IP Multicast in MPLS", IETF Draft, April 2002
Arup Aeharya, Frederic Griffoul, Furquan Ansari,"IP Multicast Support in MPLS"
Ali Boudani, Jean-Marie Bonnin, "An Effective Solution for Multicast Scalability",IETF Draft, June 2002
Baijian Yang, Prasant Mohapatra,"EDGE ROUTER MULTICASTING WITH MPLS TRAFFIC ENGINNEERING"
Miercom, "Cisco MPLS based VPNS: Equivalent to the security of Frame Relay and ATM", March 30, 2001
Floyd, S. and V. Jacobason,"Random Early Detection Gateways for Congestion Avoidance.", 1993.
Clark, D. and W. Fang,"Explicit Allocation of Best Effort Packet Deliver Service.