WO2015028563A1

WO2015028563A1 - Quality of service mapping in networks

Info

Publication number: WO2015028563A1
Application number: PCT/EP2014/068290
Authority: WO
Inventors: Manuel Julian Lopez Morillo; Jose Angel Perez De La Rosa; Luis Angel MUNOZ MARIN; Jean-Francois Bouquier
Original assignee: Vodafone Ip Licensing Limited; Vodafone Espana S.A.U.
Priority date: 2013-08-29
Filing date: 2014-08-28
Publication date: 2015-03-05
Also published as: ES2530542B1; ES2530542A1; WO2015028563A9

Abstract

A system and method of facilitating data transmission from a first data network using a first data-carrying mechanism to a second data network using a second data- carrying mechanism, including: mapping a data packet from the first data network to the second data network by allocating first and second labels to the data packet; mapping a first portion of quality of service information relating to the first network data packet to a field in the first label; and mapping a second portion of the quality of service information for the first network data packet to a field in the second label. Preferably the first data-carrying mechanism is IP and the second data carrying mechanism is MPLS or Ethernet. The quality of service information from the first data network in both the first and second labels is usable for applying a corresponding quality of service by network elements of the second data network. Advantageously, where the first portion of quality of service information is 3 bits long, and the second portion of quality of service information is 3 bits long, this enables up to 64 quality of service classes to be applied in the second network.

Description

QUALITY OF SERVICE MAPPI NG IN NETWORKS

Field of the Invention

The present invention relates to the transmission of data across networks of different types. In particular, the present invention relates to the transmission of data across networks of different types, in a manner that retains quality of service parameters. Even more particularly, the present invention relates to the transmission of data from an Internet Protocol (IP) network to a network with a different data-carrying mechanism, such as Ethernet or Multiprotocol Label Switching, MPLS, in a manner which retains all or at least the majority of traffic classes used by the Internet Protocol.

Background

Transport network quality of service requirements are important for many products and services utilising communication networks, particularly products and services in the fields of M2M, Automotive, mHealth, Cloud Computing and Network Virtualisation.

The Internet Protocol (I P) is an extensively deployed protocol for transmitting data across networks. It is a routing protocol that encapsulates data packets with source and destination addresses in order to route the packets across the network.

Quality of Service is typically provided in the Internet Protocol via the Differentiated Service (DiffServ) mechanism. DiffServ classifies data traffic, by placing each data packet into a limited number of traffic classes. Each router in the network is configured to differentiate traffic based on the designated class of each packet, rather than differentiating network traffic based on the requirements of an individual flow. Each traffic class can be managed differently, ensuring preferential treatment for higher-priority traffic.

DiffServ uses a 6-bit field (DS field) in the header of an I P encapsulated packet for quality of service classification purposes. This 6 bit field enables up to 64 different classes to be supported. In this regard, the DiffServ CodePoint (DSCP) is an 8 bit field, where three bits are the Class Selector (CS) code points, another 3 bits are the Drop Precedence (DP) and two bits designated as either Currently Unused (CU) or, for I Pv4 and IPv6, as an Explicit Congestion Notification (ECN).

Applications and usage of the 64 different traffic categories of the Internet Protocol are defined in the standards RFC 2597, RFC 2598 and RFC 2474.

The Internet Protocol has been used by extensively by telecommunications network providers in their terrestrial networks for the transmission of data, however there is presently a move away from the Internet Protocol to Multiprotocol Label Switching (MPLS). As the Internet Protocol will continue to be used in many concurrent networks, there is a need to be able to effectively transfer data between I P networks and MPLS networks.

In MPLS, a four byte label is attached to data packets, where an unstructured label value field of 20 bits is provided, as well as 3 bits for Experimental use (EXP), one bit to designate a stack bottom (S) and 8 bits for a Time to Live (TTL) field. An illustration of this label is provided in Figure 1 .

Presently, the 3 bit EXP field is used as a Class of Service field in the MPLS label. Where IP packets are mapped to such an MPLS label, it is only possible for a portion of the DSCP to be mapped, typically the CS code point field. Therefore, whilst the Internet Protocol supports up to 64 different classes of service (i.e. the 6 bit DSCP field enables 2⁶= 64 different classes), MPLS only supports 8 (i.e. the three bit field only enables 2³=8 classes). Therefore, MPLS is essentially only able to directly map the Class Selector code points, but not the Drop Precedent code points. Therefore service differentiation capability is lost when mapping packets from IP to MPLS as the 64 different classes of service must be reduced to only 8.

A corresponding problem exists in relation to effectively transferring data between I P networks and Ethernet networks. The Ethernet standard, as defined in IEEE 802.1 p, is similarly only able to support up to 8 different class of service, owing to there only being a 3-bit field for QoS. There is therefore a need to improve the Quality of Service when mapping between data-carrying mechanisms, and particularly when mapping from IP to a data carrying mechanism that provides for fewer service classes. Most specifically, this need applies to mappings for I P/MPLS networks and the I P/Ethernet networks.

Summary of the Invention

According to a first aspect, the present invention provides a method for facilitating routing of a data packet using a network element located in a second data network, where the received data packet has been transmitted across a first data network which uses a first data-carrying mechanism to the second data network which uses a second data-carrying mechanism, and the received packet has been adapted for use by the second data network, such that the method includes the network element: reading a first field of a first label associated with the data packet; and where the first field indicates that the data packet is being transmitted according to a given service quality arrangement, reading a second field of a second label; and utilising the data from the first and second fields in combination in order to provide an enhanced service quality for the data packet.

Preferably the given service quality arrangement is Assured Forwarding and the method further includes recognising the first field as defining an Assured Forwarding class by virtue of a value of the first field, such that the recognition serves as a trigger to read the second field of the second label. Advantageously, the present invention enables an increased number of QoS fields to be associated with a data packet in order to provide an enhanced quality of service for that packet. Minimal changes need to be made to network nodes/elements in order to support this aspect of the invention: network nodes need only be programmed so as to recognise an entry or value in the first field of the first data packet as defining an Assured Forwarding class. In another aspect the present invention provides a method of facilitating data transmission from a first data network using a first data-carrying mechanism to a second data network using a second data-carrying mechanism, including: mapping a data packet from the first data network to the second data network by allocating first and second labels to the data packet; mapping a first portion of quality of service information relating to the first network data packet to a field in the first label; and mapping a second portion of the quality of service information for the first network data packet to a field in the second label. Ideally the quality of service information from the first data network in both the first and second labels is combined, and accordingly used for applying a corresponding quality of service by network elements of the second data network.

Advantageously, where the first portion of quality of service information is 3 bits long, and the second portion of quality of service information is 3 bits long, this enables up to 64 quality of service classes to be applied in the second network.

Preferably the first data carrying mechanism is IP. The second data carrying mechanism is one that is configured to accommodate fewer classes of service than the first data carrying mechanism. Where the first data carrying mechanism is I P, the second data carrying mechanism may be MPLS or Ethernet.

These aspects of the invention advantageously utilise the ability of MPLS and Ethernet to allocate multiple headers/labels to packets being transmitted. For instance, for Ethernet, this ability is defined in IEEE 802.1 ad (sometimes referred to as Q-in-Q), and in MPLS the label stacking concept is defined in RFC3032 (i.e. it defines the use of the S bit value (see Figure 1 ) to know if a given MPLS label is the last label or not). Where two or more labels, are utilised, one is typically defined as an outer/service label and the other an inner/customer label. In this configuration, and where I P is the first data-carrying mechanism, a 3-bit component of the 6-bit DSCP segment is copied to an appropriate 3-bit segment of the inner label (e.g. the first three bits) and a different 3-bit component of the DSCP segment is copied to an appropriate 3-bit segment of the outer label (e.g. the last three bits). The core network is then able to extract all 6 bits and determine which of the 64 possible service classes applies to the packet (i.e. 2⁶ = 64). This aspect of the invention therefore advantageously provides a straight way to map the Internet Protocol Quality of Service (QoS) parameters, based on Differentiated Services, which are capable of supporting up to 64 different traffic categories, onto an IP/MPLS network.

It enables the level of network quality tiers to be enriched, and also increases the granularity of the Quality of Service mapping. It is a feature that has particular application for transport network modernization for evolution towards all-I P. Other aspects of the invention are set out in the attached claims.

Brief Description of the Drawings

A detailed description of the embodiments of the invention will now be described with reference to the Figures, where:

Figure 1 illustrates an example of an MPLS label;

Figure 2 illustrates a first embodiment of the invention, relating to mapping data from an IP network to an MPLS network;

Figure 3 illustrates an example of a VLAN Ethernet label ; and

Figure 4 illustrates a second embodiment of the invention, relating to mapping data from an IP network to an Ethernet network.

Detailed Description

Multiprotocol Label Switching (MPLS) is a mechanism used in such high- performance telecommunications networks which directs and carries data from one network node to the next. It can encapsulate packets of various network protocols. MPLS is a highly scalable, protocol agnostic, data-carrying mechanism.

In an MPLS network, data packets are assigned labels (see Figure 1 ). Packet- forwarding decisions are made solely on the contents of this label, without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. Accordingly, MPLS essentially creates "virtual links" between distant nodes.

MPLS is an important advance for telecommunications companies, as it enables voice, data and multimedia traffic to be converged onto a single, secure network. Communications on an MPLS network can be prioritised so that activities such as sending an email can be given lower priority than business-critical or delay-sensitive applications such as IP voice. As indicated above, however, a transitional problem exists in relation to sending a data packet from a network supported by IP, to a network supported by MPLS, since MPLS does not support QoS classes to the same degree as IP.

According to a first embodiment of the invention, however, MPLS is adapted in order to enable the 64 service classes to be retained upon a packet transitioning from a network supported by IP to a network supported by MPLS. This embodiment of the invention will be described in relation to Figure 2.

In this regard, Figure 2 shows schematically some of the network elements utilised in a network supported by MPLS. An I P packet being routed towards its destination, being that of an Enhanced Packet Core (EPC) server, would be received by an I P network element, in this case being LTE Node B, and forwarded towards the EPC server. The route to this EPC server passes at least partially through a network supporting MPLS. In Figure 2, this entry to the MPLS network is the Ingress Provider Edge (PE) router, and the LTE Node B accordingly passes the IP packet to the Ingress PE router.

The network element responsible for adapting the packet to accommodate MPLS, in this instance, is the Ingress PE Router. The Ingress PE Router performs this modification, and then forwards the adapted packet across the MPLS network, via one or more Provider Routers (P). In this instance, the exit point from the MPLS network for the destination point is the Egress PE router. To adapt the packet, the Ingress PE router creates two MPLS labels for the data packet, being an MPLS Service Label and an MPLS Trunk label. The three DSCP DP bits from the IP data packet are copied to the EXP field of one of the labels, typically the MPLS Service label. The three DSCP CS bits are copied to the EXP field of the other label, typically the MPLS Trunk label.

These two labels are then able to be used by each router through the MPLS network. For instance, the following is an example of an algorithm that may be used by routers throughout the MPLS network in order to accommodate the 64 different service classes now designated in the MPLS packets:

I F Trunk MPLS EXP 3-bits" FIXES AFxy Pattern THEN

LOOK UP "Service MPLS Label EXP 3-bits"

DETERMINE Drop Precedence

ELSE

Do Nothing

END

The AFxy pattern relates to the Assured Forwarding (AF) per hop behaviour as defined in RCF2597 and later updated by RFC3260. Assured Forwarding allows the operator to provide assurance of delivery as long as the traffic does not exceed a predefined rate. Traffic that exceeds the predefined rate faces a higher probability of being dropped if congestion occurs. Assured Forwarding defines four separate AF classes with Class 4 having the highest priority. It also defines 3 drop precedence values, so within each class, packets are given a high, medium or low drop precedence. Therefore the combination of classes and drop precedence yields twelve separate DSCP encodings from AF1 1 through AF43 as per TABLE 1 :

Class 1 Class 4

Class 2 Class 3

(lowest) (highest)

Low Drop AF1 1 AF21 AF31 AF41 Medium Drop AF12 AF22 AF32 AF42

High Drop AF13 AF23 AF33 AF43

TABLE 1

Therefore, from this table it can be seen that the Assured Forwarding concept can be defined as AFxy where x(1 ..4) defines the class and y(1 .3) defines the drop precedence.

To implement Assured Forwarding, each node extracts and uses the AF data for giving different forwarding assurances, when needed. The AF data can be used to decide what class of service (e.g. AF1 , AF2, etc.) will be penalized or dropped in case of link bandwidth congestion or when traffic exceeds the assigned buffer space and link bandwidth agreed (i.e. as per the Service Level Agreement). It also applies within each AFx class (e.g. AF13 packets will get dropped before packets in AF12 and before packets in AF1 1 ).

The present invention implemented in MPLS maps the class encodings onto the Trunk MPLS EXP 3 bits, that it is the X(1 ..4). The algorithm of the present invention recognises these bits in the MPLS label as relating to Assured Forwarding by virtue of having a value of 1 to 4. This can be achieved by reference to a comparison table having the recognised Assured Forwarding values. Where a comparison shows the MPLS label value to be an AF class, this recognition serves as the criteria to trigger the look up process (i.e. I F "Trunk MPLS EXP 3-bits" FIXES AFxy Pattern, THEN LOOK UP "Service MPLS Label EXP 3-bits ", DETERMINE Drop Precedence). That is, the network element/router will then refer to the EXP field of the Service MPLS label and use the value therefrom in order to implement drop precedence, if needed. Therefore, overall, where a router recognises the value in the Trunk EXP as defining an AF class, the packet will be allocated to an appropriate queue (i.e. preferably a queue is reserved for each AF class). By virtue of the router determining the Trunk EXP value to be an AF class, the router will know it can access the Service EXP field to obtain a Drop Precedence value. The router can extract this value for its use until a packet is dispensed with (i.e. either forwarded or dropped). The drop precedence value is typically temporarily stored relative to the AF service class, so that the two fields are combined or at least utilised in combination. Alternatively the router may access the Service EXP field when needed (e.g. upon a given queue becoming congested, in order to make a determination of which packet or packets to drop in order to relieve queue congestion).

The routers on the MPLS network are accordingly able to utilise both EXP fields by using this algorithm, and accordingly base a quality of service decision on both fields (i.e. according to a possible 64 different classes of service). A small adaptation to the intermediate routers may be required in order to enable them to implement this algorithm.

It is to be appreciated that this solution is backwards compatible with the current I P/MPLS QoS implementation, where only the Trunk MPLS label is analysed.

Advantageously this embodiment of the invention enables 64 different classes of service to be provided whilst only using a single trunk across the MPLS network from the Ingress PE router to the Egress PE router. In other words, only one trunk need be used for transporting different services with different experimental bit values.

A second embodiment of the invention will now be described in relation to Figure 4, where, an Ethernet network is adapted in order to enable the 64 service classes to be retained upon a packet transitioning from a network supported by IP to a network supported by Ethernet.

In this regard, Figure 4 shows schematically some of the network elements utilised in an Ethernet network. An I P packet being routed towards its destination, being that of a Services Server, would be received by an IP network element, in this case being a Service Client, and forwarded towards the Services Server. The route to this Services Server passes at least partially through a network supported by Ethernet. Ethernet is a networking standard for Local Area Networks (LANs), and one of the most commonly used implementations is in relation to Virtual LANs. I EEE 802.1 Q is the networking standard that supports Virtual LANs (VLANs) on an Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames, so that a single trunk may be used to transport data for various VLANs. The VLAN Ethernet tag used is illustrated in Figure 3. The tag has a 1 6 bit field, being the Tag Protocol Identity (TPID), as well as a 16 bit field with Tag Control Information (TCI). The TCI typically consists of 1 2 bits as a VLAN Identifier (VI D), 1 bit as a Drop Eligibility Indicator (DEI) and 3 bits as a Priority Code Point (PCP) field. The 3 bit field PCP field is used for Quality of Service: IEEE 802.1 p.

In Figure 4, the entry to the Ethernet network is the Ingress Edge Switch, and the Service Client accordingly passes the IP packet to the Ingress Edge Switch. The Ingress Edge Switch is a computer networking device located at the entry point of the IP network to connect the end-user to the Ethernet network.

The Ingress Edge Switch is responsible for adapting the I P packet to accommodate Ethernet. The Ingress Edge Switch performs this modification, and then forwards the adapted packet across the Ethernet network, via one or more intermediate Core Switches. The Core Switches are computer networking devices located inside the Ethernet network. In this instance, the exit point from the Ethernet network for the destination point is the Egress Edge Switch. To adapt the packet, this embodiment takes advantage of I EEE 802.1 ad (Q-inQ) enabling multiple headers to be stacked on a data packet. More specifically, the Ingress Edge Switch creates two Ethernet labels/headers for the data packet, in accordance with IEEE 802.1 ad, being a Customer VLAN header and a Service VLAN header. The three DSCP DP bits from the IP data packet are copied to 3 bits in one of the headers, typically the Customer VLAN header (i.e. 3 p-bits of the inner header/tag). The three DSCP CS bits are copied to 3 bits in the other header, typically the Service VLAN header (i.e. 3 p-bits of the outer header/tag). The 3 p-bits in each header are typically corresponding fields. These two headers are then able to be used by the one or more intermediate Core Switches in routing the packet towards its destination. For instance, the following is an example of an algorithm that may be used by the Core Switches in order to accommodate the 64 different service classes now designated in the Ethernet packets: I F "Service VLAN 3 p-bits" FIXES AFxy Pattern THEN

LOOK UP "Customer VLAN 3 p-bits"

DETERMINE Drop Precedence

ELSE

Do Nothing

END

Accordingly this algorithm enables the Core Switches of the Ethernet network to be able to access 6 bits for the QoS assessment, and accordingly base a quality of service decision on both fields in the Customer and Service headers (i.e. according to a possible 64 different classes of service). For instance, where an Ethernet switch is a blocking switch, it typically has a minimum of 8 queues, and employs a queuing algorithm, such as Weighted Random Early Discard, to manage those queues. The additional service quality information provided in the headers can be used to implement drop priority functionality in at least 4 of these queues (i.e. in the event of queue congestion, in order to determine what packet(s) are discarded first).

It is to be appreciated that we have mentioned at least 4 queues above, as the number of queues required will be at least four when implementing Assured Forwarding, since each Assured Forwarding class x(1 ..4) is ideally allocated a different QoS queue to have all of the Assured Forwarding functionality available. The drop precedence classes y(1 ..3) are then applied within each queue when a queue is congested.

A small adaptation to the Core Switches may be required in order to enable it to implement this algorithm.

A further improvement could be made to this embodiment of the invention by making use of the outer bits to route through a "privileged" network.

It is to be appreciated that in both these embodiments, were the logical criteria of the DSCP to be changed in any way, these embodiments of the invention would be able to accommodate those changes simply by changing a mapping table associated with the MPLS EXP bits/Ethernet CoS bits, so that the new DSCP definitions would be reflected in the mapping table for the MPLS EXP bits/Ethernet CoS bits.

The embodiments of the invention have been described with particular reference to I P networks being mapped to an MPLS or Ethernet network. The inventive concept may equally apply to other data network migrations where the eventual data network configuration has fewer service classes than the original data network configuration.

Further, the inventive concept has been described in relation to accommodating 64 different service classes, using two different MPLS/Ethernet labels. If however more than 6 bits were needed in the future, to accommodate further data and/or service classes, additional MPLS/Ethernet labels could be used in a corresponding manner.

Also, the inventive concept has principally been described in relation to its use in relation to Assured Forwarding. Whilst this is a preferred embodiment, the invention could also be applied to other 6-bit QoS implementations. For example, if in the future a new QoS logic was defined based on 6 bits, the inventive concept could also be adapted to apply to the new logic, so as to provide QoS values of 6 bits in MPLS and Ethernet. As a specific example, if in the future it was decided to put drop precedence 1 , 2 and 3 in BE (Best Effort) Class of Service, the drop precedence of BE (e.g. BE1 , BE2, BE3) could be adapted in a similar way to the preferred embodiment for AF classes of service.

Additionally, the invention has principally been described in relation to traversing from an I P network to one typically supporting fewer service classes, such as MPLS/Ethernet networks, however the solution is backward compatible.

The embodiments of the invention also apply to newly developed network configurations, as well as upgrades made to existing network configurations.

The embodiments of the invention have particular application to data sent at least partially across a mobile network, particularly mobile networks implementing Long Term Evolution, LTE. In this regard, network quality is of particular importance when developing mobile networks, both in terms of speed and coverage reliability.

Claims

1 . A method for facilitating routing of a data packet using a network element located in a second data network, where the received data packet has been transmitted across a first data network which uses a first data-carrying mechanism to the second data network which uses a second data-carrying mechanism, and the received packet has been adapted for use by the second data network, such that the method includes the network element:

reading a first field of a first label associated with the data packet;

and where the first field indicates that the data packet is being transmitted according to a given service quality arrangement, reading a second field of a second label ; and

utilising the data from the first and second fields in combination in order to provide an enhanced service quality for the data packet.

2. The method of claim 1 wherein the given service quality arrangement is Assured Forwarding and the method further includes recognising the first field as defining an Assured Forwarding class by virtue of a value of the first field, such that the recognition serves as a trigger to read the second field of the second label.

3. A method of facilitating data transmission from a first data network using a first data-carrying mechanism to a second data network using a second data- carrying mechanism, including :

mapping a data packet from the first data network to the second data network by allocating first and second labels to the data packet;

mapping a first portion of quality of service information relating to the first network data packet to a field in the first label; and

mapping a second portion of the quality of service information for the first network data packet to a field in the second label.

4. The method of any one preceding claim further including applying a service quality to the packet transmitted across the second network using the quality of service information located in both the first label and the second label.

5. The method of any one preceding claim 1 wherein the quality of service information from the first data network in both the first and second labels is usable for applying a corresponding quality of service by network elements of the second data network.

6. The method of any one preceding claim where the first portion of quality of service information is 3 bits long, and the second portion of quality of service information is 3 bits long, and the method includes utilising the first and second portions of quality of service information from the first and second labels in combination in order to apply up to 64 quality of service classes for the transmission of data packets across the second network.

7. The method of any one preceding claim further including incorporating an indicator in the first label in order to indicate that quality of service information is also included in the second label.

8. The method of any one preceding claim where the first and second labels have the same format, and the field in the second label is an equivalent field to the field of the first label.

9. The method of any one preceding claim where the first portion of quality of service information is mapped from a first portion of a quality of service field of the first network data packet and the second portion of quality of service information is mapped from a second portion of the quality of service field.

10. The method of any one preceding claim where the first data-carrying mechanism is Internet Protocol, I P.

1 1 . The method of any one preceding claim where the second data-carrying mechanism is Multiprotocol Label Switching, MPLS.

12. The method of any one of claims 1 to 1 0 wherein the second data-carrying mechanism is Ethernet.

13. A network element configured to perform the method according to any one of claims 1 to 12.

14. A network element located in a second data network, and adapted to facilitate routing of a received data packet, where the received data packet has been transmitted across a first data network which uses a first data-carrying mechanism to the second data network which uses a second data-carrying mechanism, and the received packet has been adapted for use by the second data network, the network element being configured to:

read a first field of a first label associated with the data packet;

15. A communication system including at least first and second network elements located in a second data network, which are adapted to facilitate routing of a received data packet, where the received data packet has been transmitted across a first data network which uses a first data-carrying mechanism to the second data network which uses a second data-carrying mechanism, such that:

the first network element is configured to adapt the received data packet for use on the second data network by:

mapping the received data packet from the first data network to the second data network by allocating first and second labels to the data packet; mapping a first portion of quality of service information relating to the first network data packet to a first field in the first label;

mapping a second portion of the quality of service information for the first network data packet to a second field in the second label; and

forward the adapted packet towards the second data network element; the second network element is configured to: read the first field of the first label associated with the adapted data packet;

where the first field indicates that the data packet is being transmitted according to a given service quality arrangement, read the second field of the second label ; and

utilise the data from the first and second fields in combination in order to provide an enhanced service quality for the data packet.

16. The communication system of claim 15 wherein the second data network utilises an MPLS data-carrying mechanism or an Ethernet data-carrying mechanism, and the data packet has been transmitted from another network utilising an Internet Protocol data-carrying mechanism, and adapted for use by the first data network, such that the first and second quality of service fields correspond to quality of service fields from the Internet Protocol.