Patent Publication Number: US-7710974-B2

Title: Method and apparatus for dynamically allocating traffic in a physical layer device

Description:
BACKGROUND 
     1. Field of the Disclosure 
     The disclosure relates generally to data traffic flow in physical layer devices. 
     2. The Prior Art 
     As the capacity in computer networks have increased, providing access to such capacity to the desktop remains a challenge for designers. As the last link to a user&#39;s computer is typically a copper link such as a cable, this link is often the limiting interface in a network. 
     One disadvantage of newer devices compliant with faster-rate standards such as 10 Gigabit Ethernet (10 GE) is that devices typically do not provide for auto-negotiation between devices to establish links at rates lower than 10 Gbps. In other words, newer generation 10 Gbps equipment may not be able to establish links with legacy devices at lower link rates (such as 2.5 Gbps), especially over extended copper lines that typically feed desktop units. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         FIG. 1  is a conceptual block diagram of a 10 Gigabit Ethernet device configured in accordance with the teachings of this disclosure. 
         FIGS. 2A-2B  are flow diagrams of methods for dynamically allocating bandwidth in a physical layer device according to the teachings of this disclosure. 
         FIG. 3  is a further flow diagram of a method for dynamically allocating bandwidth in a physical layer device according to the teachings of this disclosure. 
         FIG. 4  is a conceptual diagram of a system dynamically allocating bandwidth in accordance with the teachings of this disclosure. 
         FIGS. 5A and 5B  are diagrams of a system configured to dynamically allocate bandwidth based upon system conditions. 
     
    
    
     DETAILED DESCRIPTION 
     Persons of ordinary skill in the art will realize that the following description is illustrative only and not in any way limiting. Other modifications and improvements will readily suggest themselves to such skilled persons having the benefit of this disclosure. In the following description, like reference numerals refer to like elements throughout. 
     This disclosure may relate to data communications. Various disclosed aspects may be embodied in various computer and machine readable data structures. Furthermore, it is contemplated that data structures embodying the teachings of the disclosure may be transmitted across computer and machine readable media, and through communications systems by use of standard protocols such as those used to enable the Internet and other computer networking standards. 
     The disclosure may relate to machine readable media on which are stored various aspects of the disclosure. It is contemplated that any media suitable for retrieving instructions is within the scope of the present disclosure. By way of example, such media may take the form of magnetic, optical, or semiconductor media, and may be configured to be accessible by a machine as is known in the art. 
     Various aspects of the disclosure may be described through the use of flowcharts. Often, a single instance of an aspect of the present disclosure may be shown. As is appreciated by those of ordinary skill in the art, however, the protocols, processes, and procedures described herein may be repeated continuously or as often as necessary to satisfy the needs described herein. 
     Accordingly, the representation of various aspects of the present disclosure through the use of flowcharts should not be used to limit the scope of the present disclosure. 
       FIG. 1  is a diagram of a 10 Gigabit (GB)-compliant device  100  configured in accordance with the teachings if this disclosure. In preferred embodiments, devices of this disclosure may be compliant with a standard such as the IEEE 802.3ae standard, and may be referred to as a 10 GE system. 
     Generally, the device  100  may be configured to provide optional interface capabilities between the MAC and the PHY, such as a XAUI interface between the MAC  113  and the PHY  130 . Such additional structure has been omitted for clarity, and is readily available to those of ordinary skill in the art. 
     More specifically, the device of  FIG. 1  includes an ASIC  110 , typically configured to provide a switching fabric, that is coupled to a Media Access Controller (MAC)  113 . As will be appreciated by those of ordinary skill in the art, the various elements of  FIG. 1  may also be incorporated into a single device or ASIC. The device  100  may also include a host processor  111  and associated memory  112  for operating the device in accordance with the teachings of this disclosure. 
     As is known in the art, a 10 GE system provides for four links, or lanes, designated collectively as lanes 120. In a 10 GE system, each of the lanes is operated so to transport a maximum of 2.5 Gbps, or one-fourth of the maximum bandwidth, between the MAC  113  and a PHY  130 . 
     The PHY  130  may include logic  131  configured to provide a Media Independent Interface (MII)  114  enabling the ASIC  110  to control the configuration and operation of the PHY  130 . The PHY  130  may send and receive traffic through one or more ports  132  over a medium  140  such as copper or optical fiber to one or more client devices  150 . 
     As will now be appreciated, a challenge exists in connecting a set of client devices to the PHY so as not to exceed the 2.5 Gbps bandwidth capacity on any particular lane. Embodiments for dynamically coupling client devices to the host device will now be disclosed. 
       FIG. 2A  is a flow diagram of a method for dynamically allocating bandwidth in a physical layer device according to the teachings of this disclosure. 
     The process of  FIG. 2A  begins in act  205 , where client device desiring to connect to a host device are ranked according to a predetermined criteria for determining the order in which the devices should be connected. It is contemplated that a wide variety of criterion may be applied, such as bandwidth requirement, Quality of Service (QoS), a predetermined priority list based on type of device, environmental factors such as time of day, or other parameters. The devices are then connected in act  215  in the order negotiated according to the connection criteria. 
       FIG. 2B  shows one example of a connection process using bandwidth requirement as a connection criteria. 
     The process of  FIG. 2B  begins in act  200  where the bandwidth requirements for client devices are determined. The client devices are then ranked in act  210  in descending order based on bandwidth requirement. The client devices are then connected to host device in descending order in act  220 . 
       FIG. 3  is a flow diagram of a further method for dynamically allocating bandwidth in a physical layer device in accordance with the teachings of this disclosure.  FIG. 3  shows a more detailed process using device bandwidth requirement as a connection criterion, though other criteria may also be utilized. 
     The process of  FIG. 3  begins in act  300 , where a subset of client devices desiring to connect to a host device are allocated to a particular data lane. In act  310 , the client devices are ranked in descending order of bandwidth requirement. Having determined the bandwidth requirement for the client devices, the highest requirement client device is then connected to the host device in act  320 . 
     The process then moves to query  330 , where it is determined whether the bandwidth limit has been exceeded for the particular data lane. If there is still available bandwidth, the next highest requirement client device is connected to the host through the data lane in act  340 . If it is determined that there are still client devices left in the subset to connect to the host device in query  350 , the process loops to query  330  until either all of the client devices are connected or available bandwidth is allocated. 
     If the bandwidth of the data lane is exceeded with client devices remaining to be connected, then any remaining ports allocated on the host device for the client device subset may be disabled in act  360 . 
     Although  FIG. 3  discusses assignment of traffic based on a lane, this could be performed in other methods, such as timeslotting traffic over all four lanes at once. The advantage here is that physical layer devices may not be able to communicate over a single lane at once. Thus, such a mechanism would allow for better compatibility with current 10 GE Physical Layer Devices and MACs. 
     Alternatively, a lane may be defined at the beginning of a connection to represent either a single path for traffic, or the portion of total bandwidth associated with a single path of traffic. For example 1 lane of traffic has 2.5 G of bandwidth or _ the bandwidth of a 10 GE interface. Likewise  4  lanes of traffic would evenly divide the bandwidth of a 10 GE interface. Though this example relates to 10 GE interfaces, the teachings of this disclosure may apply to other protocols or capacities as well. 
       FIG. 4  is a conceptual diagram of a system  400  dynamically allocating bandwidth in accordance with the teachings of this disclosure.  FIG. 4  shows a PHY  430  coupled to a MAC  410  through a XAUI compliant 10 GE interface  420 . Though the PHY is shown coupled to a MAC on the host device, it is to be understood that PHYs of this disclosure may be coupled to any desired part of the host device, such as an ASIC or switch. 
       FIG. 4  also includes ports  440  for coupling client devices (not shown) to the PHY  430 .  FIG. 4  shows an embodiment where 10 ports are provided, other configurations are possible. As will be appreciated by those of ordinary skill in the art, the 10 Gigabit capacity of the interface  420  is distributed by allocating 2.5 G/bit streams of traffic across each of the four lanes 1-4 of interface  420 . In a preferred embodiment, a subset of ports  440  is allocated to a particular lane of interface  420 . Hence, traffic through ports  1 - 5  is shown being allocated to lanes 1 and 2 of interface  420 , and traffic through ports  6 - 10  being allocated to lanes 3 and 4 of interface  420 . 
     Furthermore, particular ports may be allocated to a specific data lane. For example, ports  1  and  2  may be assigned to pass traffic through lane 1, ports  3  and  4  may be assigned to pass traffic through lane 2, and so on. In the example of  FIG. 4 , as five ports cannot be evenly divided between two data lanes, the system  400  may be configured to share traffic through port 5 between lanes 1 and 2 using techniques known in the art, such as buffering in the PHY. The traffic flowing through ports  6 - 10  may be allocated through lanes 3 and 4 in a likewise manner. 
     Examples of lane negotiation will now be provided. 
     In a first example, an ASIC is assumed to have a XAUI interface and it is desired to connect to a 5 G/bit PHY and two 2.5 G/bit PHYs. In accordance with the teachings of this disclosure, lane 1 would negotiate to 5 Gig, then lane 3 to 2.5 Gig followed by lane 4 to 2.5 Gig. Lane 2 would not need to negotiate a speed, since it was done by lane 1 due to the necessity of splitting the 5 G/bit traffic between the first two lanes. As will now be appreciated, the system of this disclosure is preferably configured to utilize negotiation information from one lane to influence traffic/MAC/PHY/negotiation setup across the other lanes of traffic, as illustrated in the previous example. In other words, how the link as a whole is brought up depends on PHY configuration and negotiations on one lane determining the configuration and negotiation of other lanes. Thus, in the previous example, if the 10 GE lane 1 is negotiated to 5 G/bit, then lane 2 (the adjacent lane) must not negotiate. 
     In a further example, it is assumed a 10 G XAUI interface is present between an ASIC and a 10 G XAUI PHY. On the link side of the PHY interface are ten—10/100/1000/2500 interfaces. It is desired to connect two—2.5 G/bit devices, and five 1 G devices. 
     As disclosed above, the highest bandwidth devices will be connected first. Additionally, it is assumed that a subset of port pairs will be allocated to each lane, with one or more ports sharing bandwidth from multiple lanes. 
     Accordingly, the first port links the first 2.5 G device with lane 1, forcing the 2nd port to be disabled or alternatively using spare XAUI bandwidth across the XAUI&#39;s first lane. Such a configuration may require buffering in the PHY. 
     The third port may negotiate to the second 2.5 G device using bandwidth from the second lane. Assuming ports  1 - 5  are allocated to lanes 1 and 2, this would force the 4th and 5th ports to be disabled or slow. 
     The balance of the 1 G devices may negotiate with ports  6 - 10 , where ports  6  and  7  use bandwidth from lane 3, and ports  9  and  10  use bandwidth from lane 4. In this example, port  8  may obtain bandwidth 50% from lane 3 and 50% from lane 4. 
     Thus, in this example, the PHY will configure as: 
     Port  1 : 2.5 G 
     Port  2 : Disabled/spare bandwidth 10 Mbps 
     Port  3 : 2.5 G 
     Port  4 : Disabled/spare bandwidth 10 Mbps 
     Port  5 : Disabled/spare bandwidth 10 Mbps 
     Port  6 : 1000M 
     Port  7 : 1000M 
     Port  8 : 1000M 
     Port  9 : 1000M 
     Port  10 : 1000M 
     This lane/port negotiation preferably occurs at the link layer, with the results used on other lanes/ports configurations. It is contemplated that the lane/port negotiation may be accomplished in a variety of manners. For example, the MAC may configured based on the PHY negotiating a connection, with the configuration communicated through interfaces known in the art, such as a MII. Likewise, the MAC may control the connection process by polling connections desired by client devices. It is contemplated that the host device, such as a switch, may configure connections utilizing the host device&#39;s microprocessor and associated components. Alternatively, the negotiation disclosed herein of this disclosure may be performed by the PHY, wherein the logic or processor present on the PHY may be programmed to perform the negotiation. 
     It is contemplated that multiple ports may be connected to a single lane if bandwidth permits. For example, two 1 G ports may be routed into a single 2.5 G lane. In this case, the traffic may be multiplexed. 
     It is contemplated that sharing data across lanes will allow better traffic throughput on a port. For example, five 1 G ports may communicate across two 10 GE Lanes (2.5 gigabit each), requiring that some traffic from at least one port must be occur on both lanes. It is contemplated that a round robin scheme may be employed where traffic from each port takes space on all lanes. 
     As will now be appreciated, a single PHY footprint can handle multiple interfaces. For example, a single device may be provided as a 10/100/1000, 10/100/1000/2500, or 10/100/1000/2500/5000 system, using the auto-negotiation techniques disclosed herein. 
       FIGS. 5A and 5B  are diagrams of a system  500  configured to dynamically allocate bandwidth based upon system conditions.  FIGS. 5A-B  show a plurality of client devices coupled to a switch  520  through links  510 . The switch  520  is coupled to a network  540  such as an Intranet or the Internet through an Ethernet link  530 . 
     In the example of  FIG. 5A , an example of a typical enterprise network during the workday is shown, with the link speed for each respective device being shown adjacent to each link. The, less-resource intensive devices such as IP Phones and RFID readers are allocated spare bandwidth (10M), while the wireless interfaces are given full bandwidth. 
     It is contemplated that upon switch power-up, a resident installer programs the ports as shown in  FIG. 5A . 
     During the day, the computers consume some if not all of the bandwidth given to them. However, when the employees go home, some links go down allowing the PHYs of the other devices to re-negotiate to better levels. 
       FIG. 5B  shows the state of the system  500  after-hours, with the user&#39;s computers turned off. At night, scheduled backups may be performed, and hence the SAN has bumped up from 1 G to 2.5 G and the IP Phones to 100M. It is contemplated that this renegotiating may be triggered when the switch senses a link going down, such as when a computer is turned off or otherwise becomes idle. 
     It is contemplated that the system may utilize a variety of environmental factors as connection criteria. For example, may be configured to sense when a link is no longer being utilized may trigger the switch to re-evaluate the needs of device still actively connected. Additionally, the switch may be configured to determine a optimum time to optimize existing connections, such as after hours. Alternatively, the switch may be configured to determine when an optimization may be required, such as by sensing based on traffic patterns or current number of open TCP connections. The switch may also poll each device in turn at pre-defined intervals and optimize each device in sequence. 
     While embodiments and applications of this disclosure have been shown and described, it would be apparent to those skilled in the art that many more modifications and improvements than mentioned above are possible without departing from the inventive concepts herein. The disclosure, therefore, is not to be restricted except in the spirit of the appended claims.