Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2000-07-12
2004-09-14
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S395100
Reexamination Certificate
active
06791985
ABSTRACT:
FIELD OF INVENTION
The invention relates to transport of data in ATM format between ATM networks over a multi-protocol communications network using multi-protocol label switching.
BACKGROUND OF INVENTION
There are a large number of communications networks of different kinds, each being designed specifically for different purposes. These networks converge form a large network. User traffic of one type must traverse many diverse networks, each operating by different paradigms and requiring different protocol stacks, before it reaches the destination. MPLS (Multiprotocol Label Switching) is being developed to solve some of the problems which involve the existence of different protocols along the traffic path.
For example, as a packet of a connectionless network layer protocol, such as Internet protocol, travels from one router to the next, each router makes an independent forwarding decision for that packet. Each router analyzes the packet's header, and each router 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.
Packet headers contain considerably more information than is needed simply to choose the next hop. Choosing the next hop can therefore be thought of as the composition of two functions. The first function partitions the entire set of possible packets into a set of “Forwarding Equivalence Classes (FECs)”. The second maps each FEC to a next hop. Insofar as the forwarding decision is concerned, different packets which get mapped into the same FEC are indistinguishable. All packets which belong to a particular FEC and which travel from a particular node will follow the same path (or if certain kinds of multi-path routing are in use, they will all follow one of a set of paths associated with the FEC).
In conventional IP forwarding, a particular router will typically consider two packets to be in the same FEC if there is some address prefix X in that router's routing tables such that X is the “longest match” for each packet's destination address. As the packet traverses the network, each hop in turn reexamines the packet and assigns it to a FEC.
MPLS is being developed as a technique which attempts to use the network resources, such as bandwidth, more efficiently, while preserving services, e.g., QoS. It can carry any network layer protocol.
IETF-MPLS-ARC-06 “Multiprotocol Label Switching Architecture” by Rosen et al, August 1999 describes in detail the architecture of MPLS.
In MPLS, the assignment of a particular packet to a particular FEC is done just once, as the packet enters the network. The FEC to which the packet is assigned is encoded as a short fixed length value known as a “label”. When a packet is forwarded to its next hop, the label is sent along with it; that is, the packets are “labeled” before they are forwarded.
At subsequent hops, there is no further analysis of the packet's network layer header. Rather, the label is used as an index into a table which specifies the next hop, and a new label. The old label is replaced with the new label, and the packet is forwarded to its next hop.
In the MPLS forwarding paradigm, once a packet is assigned to a FEC, no further header analysis is done by subsequent routers; all forwarding is driven by the labels. MPLS uses a label to encapsulate the native traffic and forms a labeled packet. Each MPLS node switches labeled packets to a next MPLS node using labels. An MPLS packet traverses different kinds of networks one after another before it reaches the destination MPLS node which converts the packet back to its native form. It should also be noted that MPLS labels are in a fixed length which may be 0 bytes long in some environment. For example, MPLS packets can be transported through a time-slotted link e.g., TDM (time division multiplex) link. In such a case, MPLS packets are mapped at a specified timeslot on the link. Once such a link is established for MPLS traffic, MPLS packets no longer need to carry MPLS labels.
It should be emphasized that effort has been made to differentiate “encapsulating a payload into an MPLS labeled packet”, “placing a payload into an MPLS labeled packet”, “packetizing into an MPLS packet” and other similar expressions. It may however be possible that “encapsulating a payload into an MPLS labeled packet” at some location could mean “encapsulating a payload into an MPLS labeled packet with a 0-byte label”, i.e., “placing a payload into an MPLS labeled packet”.
Customer payload comes in a variety of formats and an MPLS node must analyze it so that it can insert the payload into MPLS labeled packets with MPLS packet label having sufficient information for forwarding them properly to the next MPLS node. The MPLS packets, therefore, can be transported over different media e.g., ATM, Frame Relay, TDM, DWDM (Dense Wavelength Division Multiplex), LAN (Ethernet etc.), etc. MPLS therefore forms one MPLS domain, encompassing a variety of different kinds of networks. This has a number of advantages over conventional network layer forwarding.
As shown in
FIG. 1
, MPLS therefore enables to form one multiservice MPLS domain which encompasses a number of diverse networks, such as IP, ATM, Frame Relay, TDM, DWDM, LAN etc. Unlike other network, e.g., ATM, LAN, etc., the MPLS domain is easily scaled-up in terms of the number of connections, bandwidth administration, failure (error) management etc. In
FIG. 1
, an MPLS domain
10
can be made up of aggregation of different networks
12
. Nodes
14
and
16
at the edge of the MPLS domain contains MPLS capabilities and function as MPLS nodes handling a variety of traffic to and from external networks which include TDM, LAN, IP, Frame Relay, IP, ATM etc. In the Figure nodes
14
are communicating with one another in ATM traffic.
In one form, transport of the MPLS packet between two MPLS capable nodes is performed by such a link layer protocol as PPP (point-to-point protocol). Other link layer protocols can be envisaged for this purpose with appropriate modifications. The PPP (Point-to-Point Protocol) is well known in the field of data communication. Briefly stated, however, the PPP is designed for simple links which transport packets between two peers. These links provide full-duplex simultaneous bidirectional operation, and are assumed to deliver packets in order. The PPP consists of a way of encapsulating multi-protocol datagrams, a Link Control Protocol (LCP) for establishing, configuring, and testing the data-link connection and a family of Network Control Protocol (NCPs) for establishing and configuring different network-layer protocols. This protocol is capable of transporting MPLS packets between two MPLS capable nodes.
In order to transport ATM cells from one ATM network to another over an MPLS domain, MPLS packets must be generated at the ingress of the MPLS domain and must be converted back to ATM cell at the egress of the MPLS domain. However, if the entire ATM cell is to be encapsulated in a MPLS labeled packet, there would be a large number of bytes wasted. There exists no suitable method or system which is capable of placing ATM cells into MPLS labeled packets.
SUMMARY OF INVENTION
The present invention addresses problems of placing ATM cells into MPLS labeled packets so that ATM cells are properly transported over networks and can be regenerated at the destination MPLS node, without loss of ATM services. By this invention, therefore, ATM cells can be formed into a self-describing MPLS packet which carry necessary information concerning transmitting it over an MPLS domain to a proper destination MPLS node.
In accordance with one aspect, the invention is directed to a method of transporting ATM cells between two nodes over a multiprotocol label switching domain, hereinafter called an MPLS domain. The method comprises steps of reading an ATM header to obtain attributes of an ATM cell received at a first node, the attributes of the ATM cell including a type of ATM payload. The method f
Ashwood-Smith Peter J.
St-Denis Bernard F.
Cangialosi Salvatore
Nortel Networks Limited
LandOfFree
ATM transport over multi-protocol label switching does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with ATM transport over multi-protocol label switching, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and ATM transport over multi-protocol label switching will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3260171