CROSS-REFERENCE TO RELATED APPLICATIONS
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The present application is a continuation of U.S. patent application Ser. No. 12/984,344, filed Jan. 4, 2011 by Linda Dunbar, and entitled “Ingress Node Controlled Path Impairment Protocol,” which claims priority to U.S. Provisional Patent Application No. 61/292,587, filed Jan. 6, 2010 by Linda Dunbar, and entitled “Ingress Node Controlled Path Impairment Protocol,” all of which are incorporated herein by reference as if reproduced in their entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
REFERENCE TO A MICROFICHE APPENDIX
Modern communications and data networks are comprised of nodes that transport data through the network. The nodes may include routers, switches, bridges, or combinations thereof that transport the individual data packets or frames through the network. Some networks may offer data services that forward data frames from one node to another node across the network without using pre-configured routes on the intermediate nodes. Other networks may forward the data frames from one node to another node across the network along pre-configured or pre-established paths. In some networks, the nodes may create Ethernet-Local Area Network (E-LAN) services, where traffic that corresponds to different services may be transported along different sub-networks, e.g. by different subsets of nodes. For example, the E-LAN services may comprise Institute of Electrical and Electronics Engineers (IEEE) 802.1aq network services or Virtual Private LAN Services (VPLS).
For some premium data services, source nodes (e.g., edge nodes such as a Customer Edge node, a Service Provider Ingress node, a multiprotocol label switching (MPLS) label switched path (LSP) source node, or a provider backbone bridging (PBB)-traffic engineering (TE) traffic engineered service instance (TESI) source node) may have multiple paths, which may be purchased from different service providers, to their corresponding destination nodes. For such premium services, the optimal path from each service provider is desired to achieve the best delivery of their traffic. However, condition changes (e.g., due to congestion on transit nodes, microwave transport bandwidth being impaired due to weather, or downstream hop port changes) along the pre-established path (e.g., an LSP, a PBB-TE path, or other transport path) may necessitate changes over time.
Various techniques exist to signal path impairment; however, the known techniques are either inefficient or otherwise impractical. For example, resource reservation protocol (RSVP)-TE enables individual links to advertise its available bandwidth to all the nodes in the routing domain, but RSVP-TE is not possible if the path between the source node and the destination node traverse multiple routing domains. As another example, Internet Protocol (IP) Explicit Congestion Notification (ECN) (Internet Engineering Task Force (IETF) Request for Comments (RFC) 3168) and Transmission Control Protocol (TCP) ECN (RFC 5562) describe randomly marking on data frames in transit when congestion occurs in the middle of the network. However, some transit nodes do not detect IP frames and some egress nodes (e.g., MPLS LSPs) do not terminate all of the IP frames. Also, MPLS ECN (RFC 5129) specifies a mechanism for transit nodes to mark experimental (EXP) bits when congestion happens. However, many deployed MPLS networks already use EXP bits to mark priority, and thus the ECN (RFC 5129) mechanism cannot be implemented in those networks.
One issue with ECN (e.g., IP ECN, TCP ECN, and MPLS ECN) is that the congestion marking does not occur until congestion happens. Accordingly, when a transit link bandwidth is reduced (e.g., when a microwave transport link's bandwidth is reduced due to weather), the queue on the transit node can quickly build up. Even if the ECN (IP/TCP/MPLS ECN) scheme is used, by the time the egress node recognizes the congestion and notifies the source node, the queue on the transit node may already overflow resulting in lost packets. IEEE 802.1au specifies a sophisticated mechanism and algorithm to enable an intermediate node to indicate the congestion level to the source node. However, the quantized feedback algorithm is complicated and the source node may not need the quantity and type of information provided.
Another issue with ECN and IEEE 802.1au is that the source node may not even be able to do anything with the congestion notification. For example, the source node may only have one link out to the destination or may not have sufficient capability to switch traffic. In these circumstances, the source nodes do not need to know the congestion condition in the middle of the network. Therefore, the marking operations performed by intermediate nodes upon congestion or impairment are wasted.
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In one embodiment, the disclosure includes an apparatus comprising a node configured to transmit operation, administration, and maintenance (OAM) connectivity frames, wherein the node adds an impairment notification indication to some, but not all of OAM connectivity frames transmitted by the node, wherein the impairment notification indication indicates the node's desire to receive notification of an impairment condition along the path.
In another embodiment, the disclosure includes a network component comprising a receiver unit configured to receive MPLS-Ping frames, a circuit logic configured to add a downstream link impairment indication to responses to the MPLS-Ping frames, wherein the downstream link impairment indication comprises a type and a severity level for a path impairment condition, and a transmitter unit configured to transmit the responses to the transmitted MPLS-Ping frames.
In a third embodiment, the disclosure includes a method comprising using a reserved bit of DS flags in an Echo Request for the source node to indicate if it desires to receive the impairment condition of the downstream link on a transit label switched router, wherein a C bit allows a source label switched router (LSR) to indicate if it desires to have the link impairment condition reported by transit LSR in the Echo Reply.
These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
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For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.
FIG. 1 is a schematic diagram of an embodiment of a service based network.
FIG. 2 is a schematic diagram of a communication system that utilizes path impairment notification indications.
FIG. 3 is a schematic diagram of another communication system that utilizes path impairment notification indications.
FIG. 4 is a schematic diagram of an embodiment of a path impairment notification control field.
FIG. 5 is a schematic diagram of an embodiment of downstream path condition impairment sub-type-length-value (TLV).
FIG. 6 is a schematic diagram of an embodiment of downstream path condition sub-TLV.
FIG. 7 is a schematic diagram of an embodiment of an echo request.
FIG. 8 is a flowchart of an embodiment of a path impairment notification method.
FIG. 9 is a schematic diagram of an embodiment of a transmitter/receiver unit.
FIG. 10 is a schematic diagram of an embodiment of a general-purpose computer system.
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It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any quantity of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.
Disclosed herein are network embodiments that provide a path impairment notification only to the source nodes that are interested in getting the information such that source nodes that do not care about the path impairment along the path do not receive the path impairment notifications. As such, the intermediate nodes only mark on the paths associated with source nodes that are interested in knowing the impairment condition. The disclosed path impairment notification scheme may be implemented, for example, with connection oriented networks (e.g., MPLS LSP or PBB TE TESI), where paths are established ahead of time. If conditions along a pre-established path change over time (e.g., due to microwave transport bandwidth being changed due to poor weather or due to link failure), certain source nodes may desire to be notified of such condition changes. For example, at least some source nodes that are notified of path condition changes are able to perform operations such as switching traffic to alternative paths or adjusting admission control. The implementation of the path impairment notification scheme is optional for source nodes in a connection oriented network. In at least some embodiments, a source node may initiate use of the path impairment notification scheme by adding a path impairment notification indication to transmitted management packets such as OAM connectivity frames or MPLS-Ping TLV frames. Similarly, a source node may avoid use of the path impairment notification scheme by not adding the path impairment notification indication to management packets. In this manner, the overhead of implementing the path impairment notification scheme is appropriately limited to providing path impairment information to the source nodes that want to receive this type of information.
One environment for utilizing the path impairment notification scheme disclosed herein is in Mobile Backhaul networks, where microwave transport is widely deployed. Most microwave transport nodes adjust their bandwidth based on the weather. Even though RSVP-TE allows individual links to advertise their available bandwidth in the routing domain, end-to-end bandwidth change may not be possible in some Mobile Backhaul environments because there may be multiple routing domains from the base stations to the main switching office (MSO). If source nodes (e.g., long term evolution's (LTE's) evolved base transceiver station (eNodeB) or MSO's radio network controller (RNC)) are aware of the bandwidth change, they can perform operations such as adjusting services, requesting other base stations to accept new calls, or triggering a new performance monitoring scheme to track the condition more closely.
Another environment for utilizing the path impairment notification scheme disclosed herein is in MPLS ECN networks, where source label switched routers (LSRs) may want to be aware of the congestion along an LSP path so that proper actions can be taken. MPLS ECN (RFC 5129) specifies a mechanism for transit nodes to mark EXP bits when congestion happens. However, many deployed MPLS networks already use EXP bits to mark packet priorities, making MPLS ECN (RFC 5129) mechanism unusable for the purpose of LSP change indication.
Another environment for utilizing the path impairment notification scheme disclosed herein is to enable source LSRs to be aware of significant performance degradation on the downstream links along the LSP path. The performance degradation can be due to increased latency and/or increased delay variation. Those performance degradations may be induced by the physical layer protection scheme (e.g., link switching from active side of the ring to protect side of the ring), or it may be induced by transmission media degradation.
Another environment for utilizing the path impairment notification scheme disclosed herein is to enable source LSRs to be aware of transport media changes on the downstream links along the LSP path. For example, the link can be a fiber protected by microwave, and the source router may be carrying an application that cannot use microwave due to security concerns.
FIG. 1 illustrates one embodiment of a service based network 100. The service based network 100 may comprise a plurality of nodes 110, which may comprise switches, routers, bridges, or combinations thereof. The nodes 110 may each comprise a plurality of logical and/or physical ports and may be coupled to each other via the ports and a plurality of network links (indicated by the dashed lines). The service based network 100 may be any network that establishes services between the nodes 110. The establishment and utilization of such services may result in different nodes 110 operating at different times as source nodes, intermediate nodes, and destination nodes in the service based network 100.
For example, a service may be established between a subset of the nodes 110 (indicated by the bold solid lines). With the service established, at least one of the nodes 110 may operate as a source node that initializes use of the disclosed path impairment notification scheme by adding a path impairment notification indication to a management packet (e.g., an OAM connectivity frame or a MPLS-Ping TLV frame). In at least some embodiments, the path impairment notification indication comprises a TLV sub-field with a multi-bit impairment value, which may indicate the source node's desire to receive information regarding the impairment type and/or severity level. The path impairment notification indication also may comprise an address for the source node to facilitate sending path impairment notification responses back to the source node. Alternatively, the request can be a standalone notification request.
Any intermediate nodes that encounter path impairments (e.g., a congested port, a reduced bandwidth, or an altered port) are able to provide impairment notifications back to the source node using the path impairment notification indication provided with the management packet. The impairment notifications may include the impairment type and/or severity level, and may be set by a network operator. Alternatively, the response can be a standalone notification request. Upon receipt of any responses, the source node is able to decode impairment type information and perform operations such as: obtaining additional information regarding an impaired path indicated by the response, changing communication paths being used to avoid an impaired path indicated by the response, and reducing (but not necessarily eliminating) a data load for an impaired path indicated by the response.
FIG. 2 is a schematic diagram of a communication system 200 that utilizes path impairment notification indications. The various nodes of communication system 200 may correspond to nodes 110 of the service based network 100 or nodes of another network. As shown in FIG. 2, the communication system 200 comprises a source node 210 that communicates with a destination node 230 via one or more intermediate nodes 220A-220N. The source node 210 comprises OAM connectivity frame logic 212 configured to periodically transmit OAM connectivity frames toward the destination node 230. The source node 210 also comprises path impairment notification indication request logic 214 configured to selectively add a path impairment notification indication to OAM connectivity frames transmitted by the source node 210. The path impairment notification indication request logic 214 also enables the source node 210 to decode path impairment responses based on the path impairment notification indication and to perform appropriate operations including, but not limited to, obtaining additional information regarding an impaired path indicated by the response, changing a communication path being used to avoid an impaired path indicated by the response and/or reducing a data load for an impaired path indicated by the response.
The path impairment responses are generated by any of the intermediate nodes 220A-220N, which receive an OAM connectivity frame having the path impairment notification indication. The intermediate nodes 220A-220N respectively comprise OAM connectivity frame logic 222A-222N and path impairment notification indication reply logic 224A-224N to enable the intermediate nodes 220A-220N to reply to OAM connectivity frames having the path impairment notification indication. In some embodiments, the destination node 230 also comprises OAM connectivity frame logic 232 and path impairment notification indication reply logic 234 that enables the destination node 230 to reply to OAM connectivity frames having the path impairment notification indication. In order to generate the reply, the path impairment notification indication reply logic of FIG. 2 (logic 224A-224N and 234) also detects path impairments or receives path impairment information from a suitable detector.
As an example of the operations of FIG. 2, when periodic OAM connectivity frames (e.g., bidirectional forwarding detection (BFD) for MPLS or continuity check message (CCM) for Ethernet) is enabled between a pair of nodes (e.g., a source LSR/provider edge (PE) and a destination/LSR/PE), the frequency is on a fixed interval (usually in the magnitude of milliseconds). Since the connectivity frames (CCM and MPLS BFD) are intended to traverse along a pre-established path (MPLS LSP or PBB-TE), a transit (intermediate) node has the information on the port to the path's downstream node and is aware of the downstream link status, including impairment status, such as bandwidth being reduced, a port being altered, or a port being congested. Therefore, periodic OAM connectivity frames (MPLS BFD, Ethernet CCM) are a suitable choice for implementing a path impairment notification scheme as disclosed herein.
The path impairment notification indication described herein corresponds to a path impairment notification control field, which can be added by the source node 210 to the OAM connectivity frame. In at least some embodiments, the path impairment notification control field serves the following purposes: 1) for the source node to indicate that it desires path impairment information; and 2) to indicate the source node address for the transit node to forward path impairment notification. In such embodiments, the path impairment notification control field has the format shown in FIG. 4.
If a source node of a path cannot do anything when the path is impaired, then the source node does not have to include this optional path impairment notification control field in the OAM connectivity frame (BFD or CCM). When the path impairment notification control field is not present in the OAM connectivity frame (BFD or CCM), the transit LSR does not need to mark the path condition change indication.
If the source node can re-route the traffic to an alternative path when the normal path is impaired or altered, the source node should include the optional path impairment notification control field in the BFD/CCM connectivity frame. If this path impairment notification control field is included, the transit node can do the following when downstream link impairment (e.g., congestion or bandwidth reduction) is experienced: 1) mark on the path impairment notification control field to specify the condition of the downstream link; and/or 2) send a path condition impairment notification (a reply) back to the source LSR.
The ImpairmentValue sub-field of the path impairment notification control field can take one of the values shown in Table 1:
Port towards downstream LSR is congested
Bandwidth of the link towards downstream LSR is reduced
Port towards downstream LSR has been altered
The optional Routable IP (or Ethernet) address in the path impairment notification control field is to enable the transit node to send a path condition impairment notification back to the source node. Since BFD/CCM control frames between a pair of nodes are exchanged very frequently, it may not be necessary for the transit node to send the path condition impairment notification every time a BFD/CCM control frame is received. In order to minimize the amount of work performed by the transit node, the source node controls whether it needs path impairment notifications from a transit node when the transit node experiences downstream link impairment. When the Routable IP (Ethernet) address is included in the path impairment notification control field portion of a BFD/CCM control frame, the transit node will send back a path condition impairment notification to the source node when impairment is encountered. Upon receiving the path condition impairment notification, the source LSR can do various actions including, but not limited to, triggering more sophisticated protocols to the transit node to find out more detailed information (e.g., Quantized Feedback defined by IEEE 802.1au), re-adjusting load balance among the multiple paths from the source LSR to the destination LSR, activating a protection path to take over the traffic, or reducing admission rate (in the case of LTE eNodeB).
When a transit node receives a BFD/CCM frame and its downstream link is impaired or altered, the transit node may do the following: 1) if the BFD/CCM does not include the path impairment notification control field, simply forward the BFD/CCM to the next hop; or 2) if the BFD/CCM does include the path impairment notification control field, then set the ImpairmentValue field (if needed) and forward the BFD/CCM to the next hop. If Routable IP/Ethernet address is included in the path impairment notification control field, the transit node may construct a path condition impairment notification message and send it to the source node.