Advanced MPLS Design and Implementation

An in-depth guide to understanding advanced MPLS implementation, including packet-based VPNs, ATM-based VPNs, traffic engineering, and quality of service Who Should Read This Book Scope and Definition Command Conventions Illustration Iconography A New Forwarding Paradigm What Is MPLS Summary WAN Technologies and MPLS Inside the Cloud Layer 3 Routing Label Switching Integration of IP and ATM Challenges Faced by Service Providers Summary MPLS Architecture MPLS Operation MPLS Node Architecture...

Assured Forwarding AF PHB

The DSCP marking of AF packets specifies an AF class and drop preference for IP packets. Packets with different drop preferences within the same AF class are dropped based on the their relative drop precedence values within the AF class. RFC 2587 recommends 12 AF PHBs representing four AF classes with three drop-preference levels in each. The Assured Forwarding PHB defines a method by which BAs can be given different forwarding assurances. The AFxy PHB defines four classes AF1y, AF2y, AF3y, and...

ATM Layers

The ATM layers explain data flow to and from upper-layer protocols such as TCP IP. These layers are as follows Physical layer Analogous to the physical layer of the OSI reference model, the ATM physical layer manages the medium-dependent transmission. The physical layer is responsible for sending and receiving bits on the transmission medium, such as SONET, and for sending and receiving cells to and from the ATM layer. ATM operates on various media from clear-channel T1 (1.544 Mbps) upward. ATM...

ATM Quality of Service QoS

Traffic management is the key feature of ATM that distinguishes it from current networking protocols and makes it suitable for deployment in high-speed networks and for providing performance guarantees in an integrated environment. ATM supports QoS guarantees composed of traffic contract, traffic shaping, and traffic policing. A traffic contract specifies an envelope that describes the intended data flow. This envelope specifies values for peak bandwidth, average sustained bandwidth, and burst...

Benefits of MPLS

Label-based switching methods allow routers and MPLS-enabled ATM switches to make forwarding decisions based on the contents of a simple label, rather than by performing a complex route lookup based on destination IP address. This technique brings many benefits to IP-based networks VPNs Using MPLS, service providers can create Layer 3 VPNs across their backbone network for multiple customers, using a common infrastructure, without the need for encryption or end-user applications. Traffic...

Book Advanced MPLS Design and Implementation Section Virtual Private Networks

To address the unique needs and requirements of varied enterprise customers, service providers should consider using both MPLS and IPSec in their VPN deployment mix. Each of these technologies has its relative strengths and complements the other in an end-to-end secure VPN environment extending over the service provider's secure infrastructure as well as circuits over the public Internet. The decision matrix in Table 4-1 provides a comparison of the various VPN technologies and recommendations...

Case Study of a Packet Based MPLS over Atm Vpn

Consider the service provider shown in Figure 6-19. It has points of presence (PoPs) in Chicago, Seattle, San Diego, Miami, and Washington. The service provider can offer Layer 3 IP VPN services across its MPLS backbone. The service provider offers MPLS VPN services to three customers A, B, and C. Backbone ATM switches have replaced the core P routers. The customers are each operating a single VPN. Figure 6-19. Case Study Packet-Based MPLS over ATM VPN Configuration T72 lfl. HO fli 172 17. l 0...

Case Study of an Mpls Vpn Design and Implementation

Consider a service provider with points of presence in Chicago, Seattle, San Diego, Miami, and Washington. The service provider offers layered IP VPN services across its MPLS backbone. The service provider offers MPLS VPN services to three customers A, B, and C. The detailed architecture is shown in Figure 5-3. The customers are operating a single VPN each. Figure 5-3. Case Study Service Provider Network Figure 5-3. Case Study Service Provider Network The service provider has provisioned the...

CE1 Configuration

A partial configuration for the customer edge router CE1 is as follows Figure 5-17. Internet Connectivity Using EBGP Multihop Sessions Figure 5-17. Internet Connectivity Using EBGP Multihop Sessions interface loopbackO ip address 10.2.2.1 255.255.255.0 interface ethernet0 0 ip address 150.100.2.1 255.255.255.0 interface serial0 0 ip address 20.2.2.1 255.255.255.0 router bgp 2 neighbor 64.2.2.2 remote-as 25431 neighbor 64.2.2.2 ebgp-multihop 255 neighbor 64.2.2.2 update-source loopbackO neighbor...

Introduction to MPLS

This chapter covers the following topics A New Forwarding Paradigm This section discusses conventional technologies versus Multiprotocol Label Switching (MPLS) techniques that are being implemented in carrier and service provider networks. MPLS is the technology that is driving future IP networks, including the Internet. MPLS gives the Internet a new forwarding paradigm that affects its traffic engineering and the implementation of VPNs. What Is MPLS This section discusses MPLS as an improved...

Advanced MPLS Architectures

This chapter covers the following topics Optical Networking This section discusses the requirement for fiber-optic network infrastructures in which switches and routers have integrated optical interfaces and are directly connected by fiber or optical network elements, such as Dense Wavelength Division Multiplexers (DWDMs). Conventional fiber-optic systems and DWDM technology are also discussed. Optical Transport Network Elements Technical details of Optical Transport Network (OTN) elements such...

ATMBased Mpls Vpns

This chapter covers the following topics Introduction to ATM-Based MPLS VPNs Service providers and carriers that currently provide ATM and Frame Relay services can utilize their existing ATM infrastructure to provide managed VPN services using MPLS. IP transport over ATM networks requires a complex hierarchy of translation protocols to map IP addresses and routing into ATM addressing and routing. MPLS eliminates complexity by mapping IP addressing and routing information directly into ATM...

Circuit Switching and TDM

Time-division multiplexing combines data streams by assigning each stream a different time slot in a set. TDM repeatedly transmits a fixed sequence of time slots over a single transmission channel. Within T-carrier systems, such as T1 E1 and T3 E3, TDM combines pulse code modulated (PCM) streams created for each conversation or data stream. TDM circuits such as T1 E1 or T3 E3 lines can be used for voice as well as data. PCM is used to encode analog signals into digital format. Voice calls need...

Class Selector PHB

Many current implementations of IP QoS use IP precedence due to its simplicity and ease of implementation. In order to preserve backward compatibility with the IP precedence scheme, DSCP values of the form xxx000 are defined (where x equals 0 or 1). Such codepoints are called class-selector codepoints. The default codepoint 000000 is a class-selector codepoint. The PHB associated with a class-selector codepoint is a class-selector PHB. These PHBs retain almost the same forwarding behavior as...

Configuration for AS1 EBGP1

The following is the configuration used for Exterior Border Gateway Protocol router 1 (EBGP1). EBGP1 is configured with the redistribute connected subnets command and interfaces with AS2. interface LoopbackO ip address 10.0.0.4 255.255.255.255 interface Ethernet0 0 description EBGP1 to P1 ip address 10.2.1.2 255.255.255.0 tag-switching ip interface Serial0 0 description EBGP1 to EBGP2 ip address 12.0.0.1 255.255.255.252 router ospf 1 log-adjacency-changes redistribute connected subnets network...

Configure a Rate Limit on an Input Interface to Set MPLS Packets

Configure a rate limit on the input interface that will throttle back the preclassified IP packets Step 1. Designate the input interface Router(config) interface interface-name Step 2. Specify the action to take on packets during label imposition Router(config-int) rate-limit input access-group rate-limit acl-index bps burst-normal burst-max conform-action set-mpls-exp-transmit exp exceed-action set-mpls-exp-transmit exp Step 3. Exit interface configuration mode Here is an example. The...

Configure the Service Policy to Attach to an Interface

The service-policy interface configuration command is used to attach the service policy to an interface and to specify the direction in which the policy should be applied. The service-policy command syntax is as follows service-policy input output policy-map-name no service-policy input output policy-map-name Step 1. Designate the input interface Router(config) interface interface-name Step 2. Attach the specified policy map to the input interface Router(config-int) service-policy input...

Connection Oriented VPNs

Connection-oriented VPNs can be built on Layer 2 or Layer 3 infrastructures. VPNs built using connection-oriented, point-to-point overlays such as Frame Relay and ATM virtual connections are examples of Layer 2 connection-oriented VPN networks. VPNs built using a full or partial mesh of tunnels utilizing IPSec (with encryption for privacy) or Generic Routing Encapsulation (GRE) are examples of Layer 3 connection-oriented VPN networks. Access VPNs are circuit-switched, connection-oriented VPNs...

Conventional IP VPNs

Many carriers provide a managed IP services offering that basically lets customers hook up their CPE IP routers to a service provider's private IP backbone. Most IP service providers run an IP network over a Layer 2 infrastructure such as an ATM or Frame Relay network. An example of a conventional IP VPN is shown in Figure 4-9. Figure 4-9. Conventional IP Router-Based VPN Network Figure 4-9. Conventional IP Router-Based VPN Network The service provider typically configures multiple routing...

Conventional Layer 3 Routing Versus MPLS

As Layer 3 packets are forwarded from one router to the next, each router makes an independent forwarding decision for that packet. Each router analyzes the destination Layer 3 address in the packet's header and runs a network layer routing algorithm. Each router independently chooses a next hop for the packet based on its analysis of the packet's header and the results of running the routing algorithm. Forwarding decisions are the result of two functions Classification of Layer 3 packets into...

Data Link Connection Identifier DLCI

A data-link connection identifier (DLCI) identifies the Frame Relay PVC. Frames are routed through one or more virtual circuits identified by DLCIs. Each DLCI has a permanently configured switching path to a certain destination. Thus, by having a system with several DLCIs configured, you can communicate simultaneously with several different sites. The User-Network Interface (UNI) provides the demarcation between the FRAD and the Frame Relay network. The combination of the UNI and the DLCI...

Deployment Options

IP-based service providers who own and manage their own router, fiber, and OTN infrastructure are more inclined to go with a peer model implementation of MP S. Providers who offer multiple services over their OTN will probably choose an overlay solution. As noted earlier, providers have the flexibility to use any combination. For example, a provider could configure a domain of IP routers and OXCs all running an MPLS- or MPA,S-based control plane to support ISP services. Some OXCs might also...

Differentiated Services Architecture

The DiffServ (DS) region is composed of one or more DS domains. Each DS domain in turn is configured using the DSCP and the different PHBs. The entire IP path that a packet travels must be DiffServ-enabled. A DS domain itself is made up of DS ingress nodes, DS internal nodes in the core, and DS egress nodes. A DS ingress or egress node might be a DS boundary node, connecting two DS domains. Typically, the DS boundary node performs traffic conditioning. As shown in Figure 8-7, a traffic...

Distribution of Constraint Based Routing Information

The distribution of constraint-based information must be performed in order to find appropriate paths through the network. LSP traffic-engineered tunnels must be routed with an understanding of the traffic load they need to carry. The constraint information must be distributed across the MPLS network in a consistent way. The flooding mechanism used by link-state routing protocols such as OSPF and IS-IS can help create an integrated constraint and forwarding database. Distance vector (DV)...

DS Framing

Two kinds of framing techniques are used for DS-level transmissions The frame formats are shown in Figure 2-3 and Figure 2-4. D4 typically uses alternate mark inversion (AMI) encoding, and ESF uses binary 8-zero substitution (B8ZS) encoding. Figure 2-3. D4 Super Frame (SF) Format Figure 2-3. D4 Super Frame (SF) Format Figure 2-4. Extended Super Frame (ESF) Format As shown in Figure 2-3, the SF (D4) frame has 12 frames and uses the least-significant bit (LSB) in frames 6 and 12 for signaling (A,...

Expedited Forwarding EF PHB

The DSCP marking of EF results in expedited forwarding with minimal delay and low loss. These packets are prioritized for delivery over others. The EF PHB in the DiffServ model provides for low packet loss, low latency, low jitter, and guaranteed bandwidth service. Applications such as VoIP, video, and online ecommerce require such guarantees. EF can be implemented using priority queuing, along with rate limiting on the class. Although EF PHB when implemented in a DiffServ network provides a...

Figure 43 Logical Frame Relay VPN Architecture

Figure 4-4 shows the physical Frame Relay network. Customers A and B both connect to various Frame Relay points of presence (POPs) using TDM local loops. The Frame Relay protocol is run between the local CPE FRAD (router) and the Frame Relay switch. The Frame Relay interworking function converts Frame Relay frames into ATM cells for transport across the ATM backbone. Figure 4-4. Physical Frame Relay VPN Architecture Figure 4-4. Physical Frame Relay VPN Architecture For more details on Frame...

Figure 45 Logical Atm Vpn Architecture

Figure 4-6 shows the physical ATM network. Customers A and B both connect to various ATM points of presence (POPs) using clear-channel TDM local loops or SONET SDH. The ATM routers at the CPE use ATM virtual circuits as a Layer 2 transport mechanism to carry IP or any other Layer 3 protocol. Figure 4-6. Physical ATM VPN Architecture

Figure 48 Virtual Private Dialup Network VPDN

The remote users initiate a dial-up connection to the Network Access Server (NAS) using PPP. The NAS authenticates the call and forwards the call via L2F or L2TP to the customer's home gateway. The home gateway accepts the call forwarded by the NAS, performs additional authentication, authorization, and terminates the user PPP session. The AAA (Authentication, Authorization and Accounting) function can also be performed by an AAA server such as a TACACS+ server. All PPP session parameters are...

Figure 510 Route Reflector Design

When considered as a whole, the route reflector and its clients are called a cluster. Other IBGP peers of the route reflector that are not clients are called nonclients. An AS can have more than one route reflector. When an AS has more than one route reflector, each route reflector treats other route reflectors as normal IBGP speakers. There can be more than one route reflector in a cluster, and there can be more than one cluster in an AS. The BGP configuration for the PE routers in Figure 5-10...

Figure 612 Connection Setup with Endpoints on the Same VSI Slave

However, a command for connection setup would require the local slave in turn to communicate with a remote slave in order to set up both endpoints of the connection. This is demonstrated in Figure 6-13. Figure 6-13. Connection Setup with Endpoints on Different VSI Slaves Figure 6-13. Connection Setup with Endpoints on Different VSI Slaves Figure 6-12 shows a simplified example of a connection setup with endpoints on the same VSI slave, and Figure 6-13 shows a connection setup with endpoints on...

Figure 65 Ordered Mode Downstreamon Demand Label Allocation

The following are the steps that occur in Figure 6-5 1. LSR1 sends a label binding request toward LSR2 in order to bind prefix 172.16.0.0 16 to a specific VCI. 2. LSR2 allocates VCI 20 and creates an entry in its LFIB with VCI 20 as the incoming label. 3. LSR2 sends a bind request toward LSR3. 4. LSR3 issues VCI 25 as a label. 5. LSR3 sends a reply to LSR2 with the binding between prefix 172.16.0.0 16 and the VCI 25 label. 6. LSR2 sets the outgoing label to VCI 25. This information is now used...

Figure 810 Mpls Llsp

PHE inlcrivtl Iron t bcl viiluf AF droppreieneru inSerned Irorn anp-bris PHE inlcrivtl Iron t bcl viiluf AF droppreieneru inSerned Irorn anp-bris Ruft loomed irom lat rtvalLie in tfw VCI fkHd AF drop preference stored Hwn ATM Clp bit. Ruft loomed irom lat rtvalLie in tfw VCI fkHd AF drop preference stored Hwn ATM Clp bit. In the case of DiffServ AF, packets sharing a common PHB can be aggregated into a FEC, which can be assigned to an LSP. This is known as a PHB scheduling class. The drop...

Figure 92 ATMBased Mpls Vpn

Traffic at the service provider's PoP-2 from customers B and C can be aggregated using an MGX 8220 AXIS shelf and can be backhauled over ATM PVCs to the nearest ATM Edge LSR. In this case, the closest Edge LSR is PE3. ATM MPLS networks with router-based Edge LSRs may also use separate access devices such as the MGX 8220 if access is required through a device that does not support MPLS services. This might be required if access is required to both IP services and ATM PVC services through a...

Figure 94 Migration Phase

Edge LSR Edge LSR Edge LSR Figure 9-4 shows a starting position with routers connected by PVPs through an ATM cloud. This has most of the disadvantages of traditional IP-over-ATM networks, including scalability and bandwidth efficiency issues. However, it can support MPLS VPN services. Edge LSR Edge LSR Edge LSR Figure 9-4 shows a starting position with routers connected by PVPs through an ATM cloud. This has most of the disadvantages of traditional IP-over-ATM networks, including scalability...

Fine Tuning the Evolving Network

Fine-tuning and engineering the network design is an ongoing process. As soon as an MPLS network is deployed, continuing design activities are required to verify the assumptions used in the initial design. The network must also be fine-tuned as new customers and PoPs are added. The ongoing process involves the following steps Perform regular traffic measurements and analysis. Measure actual PoP and link traffic, and compare these measurements against the predicted traffic and link capacities....

Guaranteed Bandwidth LSPs

RSVP extensions can be used to distribute labels as part of the resource reservation process and establish an LSP with reserved resources. Such an LSP is known as a guaranteed bandwidth LSP. As shown in Figure 8-4, if a reservation were established along a path from LSR1 to LSR3, LSR1 would consult its link-state database and select a path to LSR3 before sending a PATH message to node LSR3. This path would need to meet the bandwidth requirement constraint across all the links to support the...

Independent Control LSP Establishment

In the independent control method of LSP establishment, each LSR partitions its destination prefixes into FECs. Labels are assigned to each FEC, and the label bindings are advertised to the LSRs' neighbors. The LSRs create an LFIB using mappings between the FECs and their next hops. The LSR typically runs a unicast routing protocol such as OSPF or IS-IS and uses information provided by the unicast routing protocol to create the FEC-to-next-hop mapping. As shown in Figure 3-3, the LFIB stores...

Introduction

Ever since its inception and the introduction of commercial traffic in 1992, the Internet has grown rapidly from a research network to a worldwide commercial data network. The Internet has become a convenient and cost-effective medium for user collaboration, learning, electronic commerce, and entertainment. A common consensus is that the Internet will metamorphose into a medium for the convergence of voice, video, and data communications. The Internet has seen growth in terms of bandwidth,...

IP Precedence

The IntServ RSVP per-flow approach to QoS described in the preceding section is clearly not scalable and leads to complexity of implementation. IP precedence defined by the IETF has simplified the approach to IP QoS by adopting an aggregate model for flows by classifying various flows into aggregated classes and providing the appropriate QoS for the classified flows. Packets are classified at the edge of the network into one of eight different classes. This is accomplished by setting three...

Liberal Label Retention Mode LDP

If an LSR supports liberal label retention mode, it maintains the bindings between a label and a FEC that are received from LSRs and that are not its next hop for that FEC. An LSR may receive a label binding for a particular FEC from a peer LSR even though the LSR peer is not the next hop for that FEC. It then has the choice of whether to keep track of such bindings or discard them. If the LSR keeps track of such bindings, it may immediately begin using the binding again if the peer LSR...

Loop Detection

This method of loop control allows an LSP to form a loop, but it can detect and disconnect the loop in a short period of time. LDP and Cisco's TDP are examples of protocols that support loop detection. Loop detection makes use of the techniques used in loop survival methods such as TTL decrement and per-VC buffer space allocation on ATM switches as a loop-control mechanism. In addition to loop survival techniques, a technique known as the hop count approach is used for loop control in Cisco's...

LVC Exhaustion

The proper design of an ATM MPLS network takes into account the number of LVCs, destination prefixes, classes of service, Edge and core LSRs, merged LVCs, and links into the switch. However, these design limits have large tolerances, and in some cases they might be exceeded especially if VC merge is not being used. It is difficult to calculate exactly how many LVCs will be required. This depends on the exact shape and state of the network and the exact paths chosen by IP routing. If this can be...

Metric Manipulation Versus MPLS Traffic Engineering

IP networks exhibit poor efficiency, because the only mechanism for redirecting traffic is to change the link metrics presented to a link-state IGP such as OSPF. However, changing a link's metric can potentially change the path of all packets traversing the link. Also, these methods do not provide dynamic redundancy and do not consider the characteristics of offered traffic and network capacity constraints when making routing decisions. In an MPLS traffic-engineered network, any Label-Switched...

Modular QoS CLI

The Modular QoS command-line interface (MQC) is a provisioning mechanism in IOS software that allows for separation of packet classification configured using class maps, from policies configured using policy maps applied on the defined classes, and from the application of those policies on interfaces and subinterfaces configured using service policies. As shown in Figure 8-8, the MQC forms the basis for provisioning DiffServ, and all the QoS mechanisms are part of the class maps...

MPLS and Tag Switching Terminology

Cisco has taken the initiative to be fully standards-compliant with respect to MPLS and has migrated many Tag Switching procedures and formats to MPLS standards. IOS supports mpls commands as well as tag-switching commands. Table 6-1 compares MPLS terminology with that used in Tag Switching. Table 6-1. Tag Switching and MPLS Terminology Table 6-1. Tag Switching and MPLS Terminology MPLS (Multiprotocol Label Switching) TFIB (Tag Forwarding Information Base) LFIB (Label Forwarding Information...

MPLS and the Internet Architecture

Ever since the deployment of ARPANET, the forerunner of the present-day Internet, the architecture of the Internet has been constantly changing. It has evolved in response to advances in technology, growth, and offerings of new services. The most recent change to the Internet architecture is the addition of MPLS. It must be noted that the forwarding mechanism of the Internet, which is based on destination-based routing, has not changed since the days of ARPANET. The major changes have been the...

MPLS Label

A label is a 32-bit fixed-length identifier that is used to identify a FEC, usually of local significance. The label, which is attached to a particular packet, represents the FEC to which that packet is assigned. In the case of ATM, the label is placed in either the VCI or VPI field of the ATM header. However, if the frame is a Frame Relay frame, the label occupies the DLCI field of the Frame Relay header. Layer 2 technologies such as Ethernet, Token Ring, FDDI, and point-to-point links cannot...

MPLS QoS Implementation

Consider a case in which a customer sends IP traffic from one CE site to another. The IP precedence field (the first 3 bits of the DSCP field in the header of an IP packet) specifies the CoS. Based on the IP precedence marking, the packet is given the desired treatment, such as the latency or the percent of bandwidth allowed. The IP precedence bits are copied into the MPLS Exp field at the edge of the network. However, the service provider might want to set an MPLS packet's QoS to a different...

MPLS Redundancy Using HSRP

HSRP provides network redundancy in a way that ensures that user traffic immediately and transparently recovers from first-hop failures in network edge devices and access circuits. By sharing an IP address and a MAC (Layer 2) address, two or more routers can act as a single virtual router to the hosts on a LAN. The members of the router group continually exchange status messages by detecting when a router goes down. This HSRP group consists of an active router and a standby router to replace...

Mpls Vpn QoS Hose Model

In the hose model, the service provider supplies a customer with certain guarantees for the traffic that a particular CE router would send to and receive from other CE routers in the same VPN. It is easy for a customer to implement the hose model for MPLS QoS within the VPN, because the customer does not have to perform a detailed traffic analysis or capacity planning and specify the traffic distribution between various CE routers. The two parameters used in the hose model are the Ingress...

Mpls Vpn Support of QoS

A VPN is defined as a closed user group sharing a public network infrastructure with a set of administrative policies that control both connectivity and QoS among sites. The various MPLS QoS CoSs should be available on a per-VPN basis. Applications should receive various CoSs within the VPN. For example, real-time applications such as VoIP could receive a preferential CoS versus a file transfer. Two models are used to describe QoS in the VPN context the pipe model and the hose model. In the...

Optical Networking

The power of the Internet and the World Wide Web resides in its content. Retrieval of high-quality content from application servers such as Web servers and e-commerce sites in the shortest possible time has driven the need for speed for individual and corporate end users alike. Users are demanding affordable high-speed access services such as xDSL and cable modem access while the enterprise market pushes toward high-speed managed IP VPN services with Internet access. In an effort to retain...

Overview of VPNs

Service providers have been offering VPN (Virtual Private Network) services to enterprise customers since the inception of TDM-based networks and X.25 packet-switched data networks. More recently, Frame Relay and ATM-based networks with multiple classes of service have largely replaced X.25 and dedicated leasedline circuits. Service providers charge either a fixed or usage-based rate for VPN services. The term VPN has been in use with carriers and service providers to identify closed user group...

P3 Configuration

Config-int) service-policy input class_PHB_policy config-int) service-policy input class_PHB_policy config-int) service-policy input class_PHB_policy config-int) service-policy input class_PHB_policy Copyright 2002 O'Reilly & Associates, Inc. All rights reserved. 1005 Gravenstein Highway North Sebastopol, CA 95472 Integrated Services (IntServ) provides for an end-to-end QoS solution by way of end-to-end signaling, state maintenance (for each RSVP flow and reservation), and admission control...

Packet Based MPLS over ATM

The operation of MPLS over ATM Private Virtual Circuits (PVCs) results in an overlay model. MPLS is configured on ATM routers, which perform Provider (P) and Provider Edge (PE) router functionality. This model does not realize the full advantages of the underlying ATM QoS. However, for service providers that are running core ATM networks with non-MPLS ATM switches, MPLS can still be deployed to create VPNs or leverage the advantages of traffic engineering. Service providers can run MPLS in an...

Packet Based Mpls Vpns

Figure 9-1 shows a packet-based MPLS VPN network deployed using a router-based backbone. The links between the core P routers, PE to core P routers, and PE to CE routers can be any mix of conventional Layer 2 technologies. The MPLS header is carried as a shim header in the case of a legacy Layer 2 header or in the VPI VCI field in the case of ATM. The MPLS backbone need not be fully meshed. However, the IGP (OSPF or IS-IS) should have full connectivity, and there should be a full MP-IBGP mesh...

PE2 Configuration

A partial configuration for the provider edge router PE2 is as follows interface serial ip address 2 .2.2.2 255.255.255 . router bgp 254B1 no synchronization no bgp default ipv4-activate neighbor 64.2.2.2 remote-as 254B1 neighbor 64.2.2.2 update-source loopback neighbor 64.2.2.2 activate address-family vpnv4 unicast neighbor 64.2.2.2 activate neighbor 64.2.2.2 send-community extended exit-address-family address-family ipv4 unicast vrf VPNl redistribute static redistribute connected neighbor 1...

Per Hop Behavior PHB

As shown in Figure 8-6, network elements or hops along the path examine the value of the DSCP field and determine the QoS required by the packet. This is known as aper-hop behavior (PHB). Each network element has a table that maps the DSCP found in a packet to the PHB that determines how the packet is treated. The DSCP is a number or value carried in the packet, and PHBs are well-specified behaviors that apply to packets. A collection of packets that have the same DSCP value in them, and...

PHB Enforcement

PHB is enforced on core routers depending on the DSCP value marked on the packet. EF is implemented using Low Latency Queuing (LLQ), and AF can be implemented using a combination of CBWFQ (Class-Based Weighted Fair Queuing) and WRED or CAR. LLQ offers strict priority queuing for delay-sensitive traffic such as VoIP along the data path. LLQ must be implemented at each hop. This priority queue is policed in order to ensure that excess delay-sensitive traffic does not interfere with traffic of...

Providing a Backbone Network to a Customer Carrier Mpls Vpn Service Provider

When a backbone carrier and the customer carrier both provide BGP MPLS VPN services, the method of transporting data is different from when a customer carrier provides only ISP services. This is illustrated in Figure 5-14. Figure 5-14. Backbone Carrier Supporting a Customer Carrier Offering MPLS VPN Services Figure 5-14. Backbone Carrier Supporting a Customer Carrier Offering MPLS VPN Services When a customer carrier provides BGP MPLS VPN services, its external routes are VPN-IPv4 routes....

Quality of Service

The Internet is changing every aspect of our day-to-day lives including the way we work, study, and entertain ourselves. A major factor in the success of the Internet is its universal accessibility, ease of use, and the practical convenience of Web-related technologies. Consider a user who has subscribed to low-cost long distance with a carrier providing voice over IP (VoIP) phone service. The person placing the VoIP call would expect that call to emulate a traditional long-distance call....

R1 Configuration ISIS

The configuration of R1 is as follows interface Loopback0 ip address 10.10.10.1 255.255.255.255 ip router isis interface Tunnel0 ip unnumbered Loopback0 tunnel destination 10.10.10.8 tunnel mode mpls traffic-eng tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng priority 1 1 tunnel mpls traffic-eng bandwidth 120000 tunnel mpls traffic-eng path-option 10 explicit name r1r8_oc12path tunnel mpls traffic-eng path-option 20 explicit name r1r8_oc3path tunnel mpls traffic-eng...

Service Policy Configuration

A service policy is configured using the policy-map command to specify a service policy name. The traffic class is associated with the service policy with the class command. The QoS policies for the service policy are defined in policy map submode. The QoS policies that can be applied in the service policy in policy map submode are detailed in this section. The policy-map syntax is as follows policy-map policy-name no policy-map policy-name The class command syntax is as follows class...

Step 1 Create Traffic Classes

Create QoS traffic classes on ingress PE LSRs for the MPLS VPN. PE1 Configuration Figure 8-15 shows an MPLS VPN defined using an ATM LSR backbone. Customers A, B, C, and D have been provided MPLS QoS for various classes of traffic. The QoS traffic classes are configured on ingress PE LSRs. On PE1, notice that Customer A uses S0 0 0 as its ingress interface into the MPLS backbone, whereas Customer B uses S0 0 1 as its ingress interface. This helps the service provider differentiate between...

Synchronous Optical Network SONET

The SONET hierarchy is the optical extension to the TDM hierarchy and uses the optical carrier (OC) levels. SONET is an American National Standards Institute (ANSI) standard for North America, and Synchronous Digital Hierarchy (SDH) is the standard for the rest of the world. The basic signal is known as Synchronous Transport Signal level 1 (STS-1), which operates at 51.84 Mbps. The SONET signal levels are shown in Table 2-2. SONET systems can aggregate the T-carrier TDM systems using SONET add...

Table 21a DSLevel Hierarchy

An example of a circuit-switched network from a customer's perspective is shown in Figure 2-1. This topology is also referred to as a point-to-point line or nailed circuit. Typically, such lines are leased from a local exchange carrier (LEC) or interexchange carrier (IXC) and are also referred to as leased or private lines. One leased line is required for each of the remote sites to connect to the headquarters at the central site. Figure 2-1. Leased Lines from a Customer Perspective Figure 2-1....

The Need for Traffic Engineering on the Internet

A widespread consensus is that the Internet will transform into a multiservice medium leading to the convergence of voice, video, and data communications. Internet traffic is rising in a geometric progression, with compounded traffic growth. Although the Internet's long-term market performance is difficult to predict, one constant remains phenomenal growth. Large Internet service providers have responded to the challenge of Internet growth by implementing three complementary initiatives...

Trace Route Enhancements

Expired TTL packets do not return to a source if there is a break in the Interior Gateway Protocol (IGP) path. Currently, MPLS forwards the expired TTL packets by re-imposing the original label stack and forwarding the packet to the end of a Label-Switch Path (LSP). For provider edge routers forwarding traffic over a virtual private network (VPN), this is the only way to get the packet back to the source. If there is a break in the IGP path to the end of the LSP, the packet never reaches its...

Traffic Class Configuration

The class-map command is used to create a traffic class. In order to create a traffic class containing match criteria, the class-map command is used to specify the traffic class name, and a match command is used in class map configuration mode. class-map match-any match-all class-name no class-map match-any match-all class-name The class-map match-all command is used when all of the match criteria in the traffic class must be met in order for a packet to match the specified traffic class. The...

Traffic Engineering Capabilities

MPLS provides traffic engineering capabilities needed for the efficient use of network resources. Traffic engineering allows you to shift the traffic load from overutilized portions to underutilized portions of the network according to traffic destination, traffic type, traffic load, time of day, and so on. Copyright 2002 O'Reilly & Associates, Inc. All rights reserved. 1005 Gravenstein Highway North Sebastopol, CA 95472 Challenges Faced by Service Providers Deregulation of the...

UCP Management and Control Architecture

The Unified Control Plane (UCP) architecture provides a comprehensive and open management and control architecture. Optical network elements (NEs) within an optical network contain operating systems that are responsible for providing the network control functions, data transmission functions, and NE management functions for those elements. For the purposes of discussion, these functions can be divided into three categories Control plane Includes functions related to networking control...

UCP Overlay Model

In the overlay model, the basic premise is that there are two very distinct control planes, as shown in Figure 10-8. The routers at the edge of the network have the primary intelligence and communicate with the optical transport network via a signaling interface. The routing, topology distribution, and signaling protocols for the router and optical network are different. IP routers and OTN OXC equipment are contained in two separate administrative domains. IP routers are attached to the nearest...

VC Merge

VC merge, illustrated in Figure 6-7, allows ATM LSRs to transmit cells coming from different VCIs over the same outgoing VCI toward the same destination. This helps reduce the number of Label Virtual Circuits (LVCs) required in the MPLS network. In other words, it allows multipoint-to-point connections to be implemented by queuing complete AAL5 frames in input buffers until the end of frame is received. The cells from the same AAL5 frame are all transmitted before cells from any other frame are...

Verify the Modular QoS CLI Configuration

Verify the Modular QoS CLI configuration using the following steps Step 1. Display all traffic class information Router show class-map Step 2. Display the traffic class information for the user-specified traffic class Step 3. Display all configured service policies Step 4. Display the user-specified service policy Router show policy-map policy-map-name Step 5. Display configuration and statistics for all input and output policies that are attached to an interface Step 6. Display the...

Warning and Disclaimer

This book is designed to provide information about MPLS. Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information is provided on an as is basis. The author, Cisco Press, and Cisco Systems, Inc. shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the discs or programs that may accompany...

Washington DC[PE5[PE5

The core routers P1, P2, and P3 are fully meshed in this example. However, it is not necessary to have them fully meshed. Layer 3 Interior Gateway Routing Protocol (IGRP) running across the backbone normally provides any-to-any connectivity for IBGP peers to communicate with each other, even though the IBGP peers (PE routers) are not directly connected to each other. The IP addressing scheme used in this case study is explained in Table 5-3. Table 5-3. Case Study VPN IP Address Architecture...

Washington PE Configuration

The following is the Washington PE configuration interface atm1 0 0.1 point-to-point description atm pvc to Miami ip 10.10.45.2 255.255.255.252 pvc 5 9 encapsulation aal5snap tag-switching ip interface atm1 0 1.1 point-to-point description atm pvc to Chicago ip 10.10.15.2 255.255.255.252 pvc 6 5 encapsulation aal5snap tag-switching ip Copyright 2002 O'Reilly & Associates, Inc. All rights reserved. 1005 Gravenstein Highway North Sebastopol, CA 95472

Figure 33 Label Forwarding Information Base LFIB

Outgoing label Outgoing interface Next hop address Outgoing label Outgoing interface Next hop address Outgoing label Outgoing interface Next hop address Outgoing label Outgoing interface Next hop address Outgoing label Outgoing interface Next hop address Outgoing label Outgoing Interface Next hop address Label forwarding information base (LFIB) structure Each subentry consists of an outgoing label, outgoing interface, and next-hop address. Subentries within an individual entry may have the same...

WAN Technologies and MPLS

This chapter covers the following topics Inside the Cloud This section describes circuit, packet, and cell switching technologies. A fundamental understanding of existing WAN switching technologies will enhance your understanding of MPLS technology as applied to wide-area technology. Layer 3 Routing This section describes the forwarding and control components of the routing function and Forwarding Equivalence Classes (FECs). Label Switching An introduction to label switching and MPLS is...

Forwarding Equivalency Class

Forwarding Equivalency Class (FEC) is a set of Layer 3 packets that are forwarded in the same manner over the same path with the same forwarding treatment. While assigning a packet to an FEC, the router might look at the IP header and also some other information, such as the interface on which this packet arrived. FECs might provide a coarse or fine forwarding granularity based on the amount of information considered for setting the equivalence. A set of unicast packets whose Layer 3...

Advantages of MPLS Traffic Engineering

MPLS traffic engineering features allow an MPLS backbone to replicate and expand upon the traffic engineering capabilities of Layer 2 ATM and Frame Relay networks. Traffic engineering is essential for service provider and Internet service provider backbones. Both backbones must support a high use of transmission capacity, and the networks must be very resilient so that they can withstand link or node failures. The following are the advantages of MPLS traffic engineering With MPLS, traffic...

HSRP Support Between Two VRF Interfaces

Figure 5-18 illustrates HSRP support between the two VRF interfaces belonging to PE1 and PE2. The CE uses the virtual IP address of 10.10.10.10 as the next-hop address for its default static route. The real IP addresses of 10.10.10.1 and 10.10.10.2 are configured on PE1 and PE2. PE1 can be prioritized to remain active, and PE2 is in standby mode. The serial interfaces to the P router are tracked. This ensures that the links that experience a greater number of flaps will be automatically...

Committed Information Rate CIR

Another parameter, called the Committed Information Rate (CIR), defines an agreement between the carrier and the customer regarding the delivery of data on a particular VC. CIR is measured in bits per second. It measures the average amount of data over a specific period of time, such as 1 second, that the network will attempt to deliver with a normal priority. In the event of congestion, data bursts that exceed the CIR are marked as Discard Eligible (DE) and are delivered at lower priority or...

Optical Cross Connect

The Optical Cross-Connect (OXC) is a DWDM system component that provides cross-connect switching functionality between n input ports and n output ports, each handling a bundle of multiplexed single-wavelength signals. The OXC permits bandwidth management and supports network reconfiguration. The OXC lets service providers transport and manage wavelengths efficiently at the optical layer. An OXC contains a bit-rate and format-independent optical switch that helps it cross-connect over multiple...

Local Management Interface LMI Status Polling

The operational support protocol for the UNI is called the Local Management Interface (LMI). The LMI standards in use are ANSI T1.617 Annex D, Q.933 Annex A, and the Cisco LMI. The LMI defines a polling protocol between the FRAD and the Frame Relay switch. The FRAD periodically issues a STATUS ENQUIRY message, and the Frame Relay switch should respond with a STATUS message. The polling period is a negotiable parameter, with a default of 10 seconds. The LMI verifies link integrity, status of...

Dense Wavelength Division Multiplexing

Conventional fiber-optic systems use a single wavelength or color injected by an optical transmitter that is a light-emitting diode (LED) in the case of multimode fiber (MMF) or a laser diode in the case of single-mode fiber (SMF). Laser diodes or LEDs perform an electrical-to-optical (EO) conversion of the electrical signal. The light is injected at a precise angle into the core of the fiber-optic cable using a lens, which has a higher refractive index than the cladding. Light pulses are...

Appendix B Mpls Equipment Design Specifications

The selection of edge and core LSR equipment depends on the design and capacity planning of the service provider core network. The tables in this appendix provide equipment specifications that help the MPLS network designer select equipment based on the service type, access, and redundancy options incorporated in the design. Table B-1. MPLS ATM-Edge Equipment Specifications Relatively small numbers of async, modem, serial Frame Relay, 10-Mbps Ethernet, ISDN BRI and PRI, HSSI, E1 T1 serial, Fast...

Figure 814 Example of Mpls Vpn QoS Hose Model

The service provider also supplies VPN1 with certain guarantees of up to 45 Mbps for traffic sent by site 2 and site 3 to site 1 (site 1 ECR 45 Mbps). This traffic could be directed to site 1 from site 2 or site 3 or distributed in an arbitrary way between site 2 and site 3 and sent to site 1. In VPN2, the service provider supplies certain guarantees of up to 20 Mbps for traffic sent by site 1 to site 2 (site 1 ICR 20 Mbps). Site 1 also has an ECR of 20 Mbps, which means that site 2 can send...

Optimized Rerouting

Fast rerouting can result in suboptimal traffic-engineered paths. The key is to dynamically respond to failure as well as to new or restored paths. Thus, when a failure is detected, it is necessary to also notify the headend of the LSP tunnel. The headend can then compute a more optimal path. Traffic can then be diverted to the new LSP tunnel. This can be done without further disruption. Often missing from Layer 2 networks is a feature called bridge-and-roll or make-before-break. This is the...

MPLS Backbone Link Sizing

The following steps detail the procedures involved with MPLS backbone link sizing Step 2. Estimate traffic from each point of presence. Step 3. Estimate the unidirectional traffic matrix. Step 4. Estimate the bidirectional traffic matrix. Step 5. Design the backbone trunk topology. Step 6. Calculate estimated link bandwidths. The first step in MPLS network design is to select the size, type, and layout of the PoPs according to the considerations described in the previous section. The edge PoPs...

Appendix A Mpls Command Reference

This MPLS command reference provides tables that document the commonly used MPLS commands. Cisco's prestandard equivalent tag-switching commands are provided, along with their MPLS counterparts. Sample usage of many of these commands can be found in the case studies and examples throughout this book. For sample usage of the remaining commands listed here, refer to the IOS Command Reference and Configuration Guide. These documents are available on Cisco's documentation CD-ROM and on Cisco...

Layer 3 Routing Design

MPLS uses link-state routing protocols such as OSPF and IS-IS to determine the routes for IP traffic and LVCs. LSRs run IP routing protocols in the same way that regular IP routers do. Designing IP routing in an MPLS network is almost exactly the same process as designing IP routing for an ordinary IP network. The network can be depicted in a logical topology, and a routing topology can be ascertained. By looking at the routing topology, you can divide the network into areas, design route...

Integration of IP and ATM

The early proponents and developers of ATM envisioned it to be a ubiquitous technology, spanning the desktop, LAN, and WAN. Today, few people still cling to that vision. Instead, IP has proliferated with the explosion of the Internet. The concept of IP over anything has taken precedence over the focus on forcing ATM to behave like a legacy LAN protocol. ATM on the LAN, driven by LANE (LAN Emulation), classical IP over ATM, and MPOA (multiprotocol over ATM), has seen limited growth and has been...

New Forwarding Paradigm

From a technology perspective, the Internet has impacted our lives more than anything in the last century. Today, we see wireless handheld devices, Internet appliances, Voice over IP (VoIP) phones, webcast video, PCs, hosts, and even mainframe traffic over the Internet. The sheer growth due to the emergence of the World Wide Web has propelled IP to the forefront of data communications. Carriers and service providers are in a constant state of backbone capacity expansion. More recently, with the...

PoP Design

Frigidaire Stove Wiring Diagram

Point of presence (PoP) design constraints include the choice of access line type and equipment for the network. The location of PoPs is largely determined by user traffic and the location of population centers. Proper capacity planning must be performed prior to PoP design. The capacity-planning phase should make proper estimates and approximations for future traffic growth based on the existing customer base and anticipated customer growth and corresponding traffic growth. Oversubscription...

Multiprotocol Lambda Switching

Multiprotocol Lambda Switching (MP .S) is the optical analogy of MPLS. The MPLS control plane performs all crucial control functions for MPLS data networks. MPLS RSVP-TE extensions or CR-LSDP extensions can be applied to optical networks to unify the control plane for optical network elements. MP .S approaches the design of control planes for OXC switches and other integrated multifunctional optical switches that leverage existing control-plane techniques developed for MPLS traffic engineering....