SDH
		ATM
		Frame Relay
		MPLS
		MetroEthernet (EOF)
		LRE

PeterStar data services ensure quality and reliable communication at a rather flexible pricing system providing for reductions depending on the total capacity of subscriber terminals purchased.

MPLS Technology

MMPLS means Multiprotocol Label Switching.

MPLS technology consists in simplifying the process of data packets routing when being transited via the provider’s backbone network. Nothing changes for a customer and the structure of the customer’s networks; however due to MPLS technology extra positive properties are added to the customer’s virtual private network (VPN) (see Section “PeterStar Virtual Private IP Networks”).

Compared favorably with other methods of VPN constructing, for instance VPN based on ATM/FR or IPSec, MPLS VPN represents high scalability, possibilities of automatic reconfiguration and natural integration with other IP services, which are at present compulsorily rendered by every successful provider: Internet access, Web and mail services, hosting. Using MPLS makes it possible to create customers’ isolated networks not dependent on each other. ÌÐLS ensures the network isolation by means of applying tunnels to transmit customer traffic over the provider’s external network.

This is achieved by route declarations from the customer network skipping over the provider’s internal network by means of the protocol BGP; thereafter, having been specially configured (using an enhanced version of MultiProtocol BGP, MP BGP) they get to the networks of the same customer. As a result, routers of different customers have no route information about each other, that’s why they are not able to exchange information, i.e. the required isolation is achieved.

To combine the customer’s geographically scattered networks into a single VPN a tunnel is used between edge routers of the provider internal network. Advantages of such MPLS VPN tunnels is that they are installed automatically, plus those benefits obtained at the expense of applying MPLS technology as such: - speeded up advance over the provider network, as well as controlling Classes of Service (CoS) for the tunnels with traffic engineering.

The MPLS VPN network is divided into two areas: customer IP networks and the provider’s internal (backbone) MPLS network to combine the customer networks.

In the backbone MPLS network of the provider IP packets are advanced based on local labels rather than IP addresses.

The MPLS network consists of Label Switch Routers (LSR) directing traffic over preliminarily formed paths with label switching (Label Switching Path, LSP) in accordance with these labels’ values. The LSR device is a peculiar hybrid of an IP router and a switch; in this case the IP router capability applies of identifying network topology using routing protocols and selecting efficient traffic paths, and the switch capability applies of advancing packets using labels and local switching tables. The LSR devices are often called for short just routers; there is a certain reason for that – in case MPLS support is disconnected, they are able to advance packets based on an IP address as well.

Among the LSR devices on the provider network edge routers can be marked out (Provider Edge Router, PE), to which customers’ sites are connected via customer edge (CE) routers, and internal routers of the provider backbone network (Provider Router, P). A physical channel on which a channel-level protocol such as PPP, FR, ATM or Ethernet is run usually interconnects directly the CE and PE routers. CE and PE communicate on the basis of standard TCP/ IP stack protocols; MPLS support is required only for internal PE interfaces (and all P interfaces).

On the provider backbone network only edge PE routers are to be configured for supporting virtual private networks, therefore only they are aware of the existing VPN’s. If the network is considered from the VPN side, the provider (P) routers do not directly interact with the customer edge (CE) routers; they are just located along the tunnel between the input and output PE routers. The PE routers serve as terminal points of LSP paths between the customer sites, and the PE routers exactly attach a label to an IP packet for its transiting via the internal network of P routers.

Let’s imagine that via a PE router an invisible boundary passes splitting it into the zone of customer sites and the zone of the provider’s network core. On one side there are interfaces via which the PE router interact with the P routers; on the other – interfaces the customer sites are connected to. From one side declarations of backbone network routes come to the PE routers, from another side – declarations of routes in customer networks.

For each new customer site the PE router creates a separate routing table. An advantage for the customer is that addressing of the nodes of each separate site is carried out independently, for a variety of nodes of one site under no circumstances will get routing information from another variety of nodes of another site.

Restricting the area of routing information circulation to the limits of separate VPN’s isolates address spaces of each VPN, allowing applying within its limits both public Internet addresses and private addresses registered according to RFC 1819.

To all addresses of the address space of one VPN a prefix is added called Route Distinguisher (RD), which identifies this VPN as a unique one. As a result all addresses on the PE router, relating to different VPN will necessarily differ from each other even in case they include a coinciding part - the IPv4 address.

Routing information exchange among the sites of each separate VPN is controlled by the protocol MP-BGP (Multiprotocol BGP).

MPLS-Based Virtual Private IP Networks (IP-VPN)

- Any data can be transmitted, since the content remains unchanged along the entire path, except for replacing labels. Hence users are able to transmit SNA, SPX/IPX, IP packets with illegal addresses (RFC 1918 addresses), frames, ATM cells etc.

- As opposed to a virtual channel, the MPLS fixed path is provided as IP interface part, therefore a buyer needs to do nothing in order to use it. An MPLS-based VPN sold to an end user will contain a parameter describing the way to distinguish traffic of this VPN. For example, an IP packets stream, when arriving at the ISP’s IP interface, will be analyzed by the MPLS edge device. Those packets meeting the VPN criterion will be directed over the MPLS path for further processing.

- ÌPLS VPN can be created to support critically important applications on a round-the-clock basis. In this case an ISP determines the fixed path during the validity of the user contract.

- If we represent the IP-based service interface as a big circle, than a VPN created by means of MPLS will add a small logical tunnel toward this common interface (a small circle inside the big one). Such a tunnel is capable of transporting IP traffic using a private internal address. The second tunnel is capable of moving NetWare SPX/IPX traffic, the third – voice within packets. It should be noted that in this case a user is not limited to voice over IP only, for MPLS doesn’t depend on the protocol. Each of the VPN tunnels is capable of providing a unique quality of service.

- At the corporate level, temporary VPN’s should facilitate the organization of direct connections between the ISP’s fixed MPLS paths and a corporate network. In this case we can expect appearance of switching products for third-level local networks, in particular devices for high-class backbones supported by MPLS. One of MPLS functions consists in what Cisco calls virtual channels integration, i.e. when several MPLS tunnels are integrated to create a single tunnel. Such a structure resembles a river tributary system and extends the MPLS-based VPN on the operator network to the interoffice network and directly up to the server or customer. In case of such VPN extension the operator might have control responsibility for ensuring a continuous through control over ÑoS.