how to read data from barcode scanner in c# Figure 4-6 Nested LSP providing VPN connectivity in C#.NET

Recognize PDF-417 2d barcode in C#.NET Figure 4-6 Nested LSP providing VPN connectivity

Separating QoS Classes Multiplexing VPNs within a single tunnel helps to reduce the signaling load and forwarding table size in the core LSRs as the number and size of the VPNs increase However, once the data for multiple streams has been clustered together in a single LSP, it is hard to provide distinct management of the different flows The encoding of an MPLS label enables 3 bits to encode the differentiated services code point (DSCP) Thus, a total of eight CoSs can be set for packets within any one LSP These bits can define queuing rules and drop priorities for packets carried on the LSP In the case of an ATM-based network, there is just 1 bit available to encode the DSCP, and this is usually used simply to indicate the drop preference If a customer or service provider needs to be able to differentiate more than eight DSCPs across the core, multiple outer LSP tunnels must be set up Each outer tunnel carries a different CoS range and can be routed separately across the core The interaction between setting up multiple outer tunnels across the core to carry more CoSs and the need to minimize the number of such tunnels using VPN multiplexing on a single tunnel are examined in more detail in the section VPN Multiplexing and Class of Service The IETF Internet Draft draft-ietf-mpls-diff-ext defines methods of signaling LSPs for CoS usage and ways of determining the interpretation of the DSCP bits TE Across the Backbone MPLS TE can be used to distribute the load within a network and guarantee bandwidth and QoS by controlling the routing of the outer VPN LSP tunnels across the service provider backbone network This is essentially the same problem as TE for non-VPN traffic and is outside the scope of this book For details of the MPLS TE protocols, refer to the white paper MPLS Traffic Engineering: A Choice of Signaling Protocols from Data Connection, Ltd1

Network Management The management of a VPN falls into two categories:

Defining the logical topology of the VPN Mapping the VPN onto the service provider s physical network, including routing the VPN data across the core network

The second of these functions is always the preserve of the service provider The first feature may, however, be managed by the service provider or the customer on a self-serve basis Applicability of MPLS to VPN Types MPLS LSP tunnels can be used to provide all or part of an implementation of any of the four types of VPN The suitability of an MPLS solution to each VPN type is described in the

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MPLS for VLL Conceptually, this is the easiest application of MPLS to VPNs Each point-to-point VLL is provisioned as an LSP tunnel between the appropriate customer sites The customer is explicitly looking for the equivalent of leased lines, so it is very important that the service provider meets any bandwidth guarantees in the SLA This means that the LSP tunnels used in a VLL solution may have to be dedicated to that specific customer rather than multiplexing the VLL traffic with other VPNs It is also possible to subdivide the resources of an outer tunnel to provide the QoS for inner LSPs The point-to-point connectivity of a VLL means that each VLL is most easily provisioned at the edge LSRs by manual configuration rather than an automatic scheme for detecting the VLL peers MPLS for VPLS The most immediately obvious means of implementing a VPLS is to map the LAN segment to a unique IP multicast address perhaps using IP encapsulation of the VPN IP traffic Such a solution could use existing IP multicast technologies rather than MPLS Indeed, such approaches are offered by many ISPs today However, technologies such as Multicasting Extensions to OSPF (MOSPF) and (nonlabels) RSVP do not provide the full TE capabilities of MPLS, so the service provider has less control over how the VPLS traffic is routed across the backbone network Very large service providers with many VPLS customers may also eventually find that there are too few administratively scoped IPv4 multicast addresses to represent each of the VPN LAN segments that they need to support, forcing them either to move to IPv6 or multiplex several VPLSs on one multicast address There are 224 administratively scoped IP multicast addresses (239/8), but a service provider may want to reserve only a portion of this address space for VPN services Current MPLS label distribution protocols are specified for unicast destination IP addresses only This means that an MPLS-based implementation of a VPLS must be, for now, based on one of the following network topologies:

A full mesh of LSP tunnels connecting the customer sites, with each service provider edge LSR responsible for the fan-out to all peers Point-to-point or multipoint-to-point LSP tunnel connections to a hub LSR that handles fan-out to all sites using point-to-point LSP tunnels

In both cases, but especially for the mesh of LSP tunnels, the MPLSbased topology may use more network bandwidth in total than the IPmulticast-based solution This is because multiple copies of each packet may be sent across any given link, each copy carried within one of several