Abstract:
A new and improved Ethernet hub for providing visibility of data packet traffic in an Ethernet network is disclosed. The Ethernet hub includes a packet buffer being coupled with a plurality of network ports to enable full duplex data packet communications among connected network stations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Provisional Application No. 61511882, filed Jul. 26, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to data communication devices. More particularly, this invention is related to a new and improved Ethernet hub to enable monitoring of data packet traffic in an Ethernet network. 
       BACKGROUND OF THE INVENTION 
       [0003]    Ethernet hubs are perhaps the oldest the networking devices for connecting multiple network stations such as personal computers in a local area network (LAN) to facilitate data communications among the connected network stations.  FIG. 1  is a block diagram in which an Ethernet hub  100  with three network ports  140  to provide network connections to three computers  120 . Although only the 3-port Ethernet hub  100  is described, it can be realized that an Ethernet hub in general can have more than three network ports. Technically, the Ethernet hub  100  is a relatively unsophisticated device which just “broadcasts” any data packets it receives from each of its connected computer  120  to all the other connected computers  120 . As shown in  FIG. 1 , each computer  120  connects to the Ethernet hub  100  by a copper twisted-pair cable  130  (e.g. Category 5 cable) which includes a transmit pair  131  and receive pair  132 . The Ethernet hub  100  acts as a shared bus  110  to electrically deliver signals carrying Ethernet data packets from one computer  120  to the other two computers  120 . At any time when one computer  120  is transmitting its data packets to another connected computer  120  over the shared bus  110 , the transmitter  121  of the transmitting computer  120  takes the “ownership” of the shared bus  110  by transmitting signals along the shared bus  110  during which the transmitters  121  of the other two computers  120  are not allowed to transmit signals, the other two computers  120  can only “listen to” the signals being transmitted on the shared bus  110  via the respective receivers  122 . 
         [0004]    As can be seen, Ethernet hubs as networking devices present the following drawbacks and limitations:
       Ethernet hubs can only operate in half duplex mode. At any time only a single computer can transmit signals. If two or more connected computers are trying to send data packets via an Ethernet hub at the same time, collision would occur and corrupt the signals being transmitted. In other words, Ethernet hubs do not support full duplex communications which is much more desirable in increasing the efficiency of the data communications.   Ethernet hubs are limited to operate on copper cables such as twisted pair cables like Category 5 network cables or the like; they do not support optical fiber connections.   Ethernet hubs are limited to lower Ethernet data rate because of the signal transmission limitation of the shared signal bus. Traditional Ethernet hubs are seen only capable of operating at date rate of 10 Mbps or 100 Mbps; they are not able to operate at higher Ethernet date rate such as 1 Gbps (1000 Mbps) and 10 Gbps.       
 
         [0008]    With the advent of Ethernet switches that basically overcome the drawbacks of Ethernet hubs as described above, Ethernet hubs are rarely used today for networking computers and other network stations in a local area network. However, because an Ethernet hub always broadcasts data packets received on each network port to all the other network ports over the shared bus, it provides a simple packet sniffing capability which enables a connected computer to receive (listen to) all the data packets being transmitted from any other computers connected to the same Ethernet hub, an Ethernet hub is still often used today by IT professionals as an inline sniffing device to capture and monitor data packet traffic in an Ethernet network. 
         [0009]    Therefore, what is needed is an improved Ethernet hub such that the above discussed problems and limitations can be resolved while the data packet sniffing capability is still kept. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The foregoing and other features, aspects and advantages of the invention will become more apparent from the following detailed description when read in conjunction with the following drawings, in which, 
           [0011]      FIG. 1  is a block diagram of an Ethernet hub of priori art which connects three computers for communicating data packets over a shared bus. 
           [0012]      FIG. 2  is a block diagram of an Ethernet hub in accordance with the present invention in which a packet buffer memory is included. 
           [0013]      FIG. 3  is a block diagram of an Ethernet hub in accordance with an embodiment of the present invention which provides two aggregation monitor ports for use as an inline packet sniffing device. 
           [0014]      FIG. 4  is a block diagram of an Ethernet hub in accordance with another embodiment of present invention which provides both an aggregation monitor port and two separate non-aggregation monitor ports for use as an inline packet sniffing device. 
           [0015]      FIG. 5  is a block diagram of an Ethernet hub in accordance with the present invention which automatically configures either two copper network ports or two optical network ports as two inline ports depending on the presence status of a pluggable optical transceiver module connectable to one of the two optical network ports. 
           [0016]      FIG. 6  is a detailed circuit schematic view of generating the presence signal of a pluggable transceiver module connectable to one selected optical port in the Ethernet hub in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 2  shows an Ethernet hub  200  in accordance with the present invention which has four network ports  240  each connectable to a computer  220  (or other type of network station) by a network cable  230 . 
         [0018]    It should be noted that the 4-port Ethernet hub in  FIG. 2  is depicted for the purpose of reducing the complexity of the illustration; an Ethernet hub in accordance with the present invention can have more than four network ports. 
         [0019]    In accordance with the present invention, the improved Ethernet hub  200  as shown in  FIG. 2  is implemented with a packet buffer memory  210 . When the Ethernet hub  200  receives data packets from any of the four network ports  240 , the received data packets are temporally stored in the packet buffer memory  210 ; at the same time each of the data packets previously stored in the packet buffer memory  210  is read out in a first-in-first-out approach and is forwarded to all the other network ports except the network port from which the data packet is originally received. In other words, instead of broadcasting received data packets over a shared signal bus to all connected computers  120  as the traditional Ethernet hub  100  in  FIG. 1  does, the Ethernet hub  200  in  FIG. 2  performs a store-and-broadcast operation to each of the received data packets by means of the packet buffer memory  210 . 
         [0020]    The operations of the packet buffer memory  210  is controlled by the associated control circuitry which is responsible for both writing ingress data packets from each of the network ports  240  of the Ethernet hub  200  into the packet buffer memory  210  and reading each of the stored data packets from the packet buffer memory  210  which is then forwarded as an egress data packet to the other respective network ports  240 . An ingress data packet refers to an incoming data packet a network port  240  receives from an externally connected computer  220 , and an egress data packet refers to an outgoing data packet that is to be sent out from the network port  240  to the externally connected computer  220 . 
         [0021]    In accordance with an embodiment of the present invention, under the operations of the packet buffer memory control circuitry, ingress data packets will be discarded when the packet buffer memory  210  becomes full and is not able to accept more ingress data packets until the packet buffer memory  210  becomes available again as the result of the previously stored data packets being read out. An egress data packet may also be discarded at a network port  240  when the network port  240  becomes over-subscribed in which the total throughput of egress data packets is more than the bandwidth of the network port  240  can accommodate for. For instance, for a network port  240  operating at the date rate of 100 Mbps, when the total throughput of egress data packets toward the network port  240  is more than 100 Mbps, the network port  240  becomes over-subscribed and will drop the otherwise outgoing data packets. 
         [0022]    Because of data packet buffering provided by the packet buffer memory  210 , each network port  240  of the Ethernet hub  200  of the present invention is able to send and receive data packets simultaneously to and from the connected computer  220  without causing signal collisions. In other words, the Ethernet hub  200  in  FIG. 2  enables full-duplex communications among the connected computers  220 . 
         [0023]    Preferably, the network port  240  of the Ethernet hub  200  can be implemented with a multi-speed Ethernet PHY ASIC (Application Specific Integrated Circuit) chip such as the 10/100/1000base-T Ethernet PHY 88E1111 from Marvell Technology Group Ltd to support Gigabit Ethernet connection. Higher data rate such as 10 Gbps connection is also possible with a 10G PHY ASIC chip. 
         [0024]    Alternatively, a selected network port  240  of the Ethernet hub  200  can be implemented with an optical/electrical transceiver to send and receive data packets to and from the connected computer  220  over an optical cable  230 . The optical/electrical transceiver can be a pluggable module such as the FTLF8519P2xCL made by Finisar Corporation, which is a small form factor pluggable (SFP) optical transceiver module in compliance with an industry standard proposed by MSA (Multiple Source Agreement) Group. 
         [0025]      FIG. 3  is a block diagram of an Ethernet hub in accordance with the present invention which provides two monitor ports for use as an inline packet sniffing device. The Ethernet hub  300  in  FIG. 3  includes four network ports which are designated as a first inline port  310 , a second inline port  320 , a first monitor port  330  and a second monitor port  340 . The Ethernet hub  300  includes a packet buffer memory which is not shown in  FIG. 3  for reducing the complexity of illustration. 
         [0026]    In accordance with an embodiment of the present invention, the Ethernet hub  300  is configured in such a way that the ingress data packets of the first inline port  310  are forwarded (broadcasted) to all the other three network ports, i.e., the second inline port  320 , the first monitor port  330  and the second monitor port  340  after being stored in the packet buffer memory (not shown in  FIG. 3 ), and the ingress data packets of the second inline port  320  are forwarded to all the other three network ports, i.e., the first inline port  310 , the first monitor port  330  and the second monitor port  340  after being stored in the packet buffer memory (not shown in  FIG. 3 ). As such, the Ethernet hub  300  provides a functionality of inline packet sniffing by enabling the passage of full-duplex data packet traffic between the two computers  350  and  360  connected to the first inline port  310  and the second inline port  320  respectively, and at the same time digitally coping the two-way full-duplex data packet traffic to the first monitor port  330  and the second monitor port  340  for output to the two connected computers  370  and  380  respectively. In  FIG. 3 , both the two computers  370  and  380  are monitoring stations for capturing and analyzing the full-duplex data packet traffic running between two computers  350  and  360  connected by the Ethernet hub  300  placed as an inline device in between the two computers  350  and  360 . 
         [0027]    Because the output from each of the first and second monitor ports  330  and  340  is a digital copy of data packet traffic that aggregates the two-way full duplex data packet flow between the two inline ports  310  and  320 , the first and second monitor ports  330  and  340  are also referred to as aggregation monitor ports respectively. 
         [0028]    Optionally, the two aggregation monitor ports  330  and  340  can be configured to discard ingress data packets received by each of the aggregation monitor ports  330  and  340  from the respective connected monitoring stations  370  and  380 . This is advantageous in situations where no ingress data packets of a monitor port are allowed to interfere with the data packet traffic traveling between the two inline ports  310  and  320 . 
         [0029]    As can be seen, there exists situations when the aggregated data throughput of the full-duplex data packet traffic between two inline ports  310  and  320  is more than the bandwidth of each of the aggregation monitor ports  330  and  340  can accommodate. When such situations occur, the otherwise egress data packets will be discarded by the aggregation monitor ports  330  and  340 . For example, if the two inline ports  310  and  320  and the two aggregation monitor ports  330  and  340  operate at the same Ethernet date rate of 1 Gbps, the aggregated traffic throughput of the full duplex traffic between the two inline ports  330  and  340  can be as high as 2 Gbps, which will over-subscribe each of aggregation monitor ports  330  and  340 , and therefore, the aggregation monitor ports  330  and  340  have to discard egress data packets when over-subscription occurs. 
         [0030]    It should be noted that although only two aggregation monitor ports  330  and  340  are depicted in  FIG. 3 , the Ethernet hub  300  in  FIG. 3  can be implemented with a single aggregation monitor port or more than two aggregation monitor ports in accordance with the present invention. 
         [0031]      FIG. 4  is a block diagram of an Ethernet hub in accordance with another embodiment of present invention which provides both an aggregation monitor port and two separate non-aggregation monitor ports for use as an inline packet sniffing device. The Ethernet hub  400  in  FIG. 4  includes five network ports which are designated as a first inline port  410 , a second inline port  420 , an aggregation monitor port  430 , a first non-aggregation monitor port  440  and a second non-aggregation monitor port  450 . In accordance with the embodiment of the present invention, the Ethernet hub  400  operates similarly to the Ethernet hub  300  in  FIG. 3  except that the first non-aggregation monitor port  440  is configured to only receive a digital copy of ingress packets from the first inline port  410  and the second non-aggregation monitor port  450  is configured to only receive a digital copy of ingress data packets of the second inline port  420 . As such, each of the two non-aggregation monitor ports  440  and  450  receives the data packet traffic between two inline ports  410  and  420  only in one direction, packet drop/loss due to port over-subscription would never occur to the non-aggregation monitor ports  440  and  450 . Usually the two non-aggregation monitor ports  440  and  450  must be connected to a monitoring station  490  with two network interfaces which has to run a software program to merge the two individual data packet streams from each of the non-aggregation monitor ports  440  and  450  to establish a digital copy of the full-duplex data packet traffic running between the two network stations  460  and  470  that are connected to the two inline ports  410  and  420  respectively. Therefore, use of the two non-aggregation monitor ports usually is not as convenient as use of an aggregation monitor port for capturing the full-duplex data packet traffic between two inline ports, but it can avoid any packet drop/loss due to port over-subscription. 
         [0032]    One main advantage of the Ethernet hub  400  in  FIG. 4  in accordance with the present invention is that the Ethernet hub  400  as a single device provides both an aggregation monitor port  430  connectable to a monitoring station  480  and a pair of non-aggregation monitor ports  440  and  450  connectable to the monitoring station  490 ; a user can thus select which monitor port(s) to use based on the estimated actual throughput of data packet traffic between the two inline ports  410  and  420 . The aggregation monitor port  430  is usually used when the inline data packet traffic is light, and the non-aggregation monitor ports  440  and  450  are usually used when the inline data packet traffic is heavy and busy. 
         [0033]    Optionally, the aggregation monitor port  430  and the two non-aggregation monitor ports  440  and  450  are configured to discard their respective ingress data packets. This is advantageous in situations where no ingress data packets of a monitor port are allowed to interfere with the data packet traffic between the two inline ports. 
         [0034]    In accordance with another embodiment of the present invention, the Ethernet hub  400  in  FIG. 4  is replaced with an Ethernet switch with least five network ports which are configured as a first inline port  410 , a second inline port  420 , an aggregation monitor port  430 , a first non-aggregation monitor port  440  and a second non-aggregation monitor port  450 . The Ethernet switch  400  receives data packets from each of the network ports, store them in a built-in packet buffer memory and then forward the data packets to their respective destination port or ports based on the header info (i.e., the destination MAC address and source MAC address as specified in the Ethernet standard IEEE 802.3) of each of received data packets. In addition to storing and forwarding data packets as a traditional Ethernet switch does, the Ethernet switch  400  in accordance with the present invention forwards the ingress data packets associated with the first inline port  410  to the second inline port  420 , the aggregation monitor port  430  and the first non-aggregation port  440 , and forwards the ingress data packets associated with the second inline port  420  to the first inline port  410 , the aggregation monitor port  430  and the second non-aggregation monitor port  450 . As such, the Ethernet switch  400  in accordance with the embodiment of the invention can be used as both an Ethernet switch and an inline packet sniffing device that is provided with both an aggregation monitor port  430  and a pair of non-aggregation monitor ports  440  and  450 . 
         [0035]    The forced forwarding of data packets in an Ethernet switch for the purpose of monitoring data packet traffic regardless of the destination MAC address information in the data packets is also referred to as “port mirroring”. The Ethernet switch as described herein provides a novel approach of mirroring data packets to both an aggregation monitor port and a pair of non-aggregation ports by a single device. 
         [0036]      FIG. 5  is a block diagram of an Ethernet hub in accordance with the present invention which includes at least two copper network ports and at least two optical network ports, wherein either a pair of copper network ports or a pair of optical network ports are configured as two inline ports based on the presence status of a pluggable optical transceiver module connectable to one of the optical network ports. As shown in  FIG. 5 , the Ethernet hub  500  has five network ports including three copper network ports  510 ,  520  and  530  and two optical network ports  540  and  550  which are connectable to their respective network stations  560 ,  562 ,  564 ,  566  and  568 . Each copper network port, typically implemented with an RJ45 jack, sends and receives Ethernet signals (e.g., 10/100/1000Base-T Ethernet) to and from its connected network station over a copper cable 570 of twisted wire pairs (e.g., Cat5e network cable), and each optical network port sends and receives Ethernet signals (e.g. 1000Base-X Ethernet) to and from its connected network station over a optical cable  580  which usually consists at least two optical fibers for full duplex signal transmission. According to the present invention, each of the two optical network ports  540  and  550  on the Ethernet hub is an electrical interface adapted for connecting to a pluggable optical transceiver module ( 545 ,  555 ) which performs the conversions between optical and electrical signals. An example of such a pluggable optical transceiver module is the FTLF8519P2xCL made by Finisar Corporation, which is a small form factor pluggable (SFP) optical transceiver module in compliance with an industry standard specified by the MSA (Multiple Source Agreement) Group. 
         [0037]    According to an embodiment of the present invention, the Ethernet hub  500  detects if or not the pluggable optical transceiver module  555  is being connected/engaged with the optical network port  550 , and then executes one of two prescribed packet forwarding schemes according to the presence status of the pluggable optical transceiver module. If the optical transceiver module  555  is detected being present on the selected optical network port  550 , the two optical network ports  540  and  550  are selected as the two inline ports and therefore the ingress data packets received on each of the optical inline ports  540  and  550  are forwarded (broadcasted) to all the other network ports including the other optical inline port. If the optical transceiver module  555  is not detected being present on the optical network port  550 , two selected copper network ports  510  and  520 , are configured as the two inline ports and therefore the ingress data packets received on each of the two copper inline ports  510  and  520  are forwarded to all the other network ports including the other copper inline port. In this case, of course, the optical port  550  will not be usable because it is not connected with the pluggable optical transceiver module  555 . 
         [0038]    According to the present invention, the Ethernet hub  500  configures the packet forwarding scheme from two prescribed packet forwarding schemes after a circuit reset (e.g., a power on reset) to the Ethernet hub  500  based on the presence status of the pluggable optical transceiver module. In other words, a packet forwarding scheme is configured automatically during the initialization process of the Ethernet hub according to the presence status of the pluggable transceiver module after a circuit reset is applied or occurs to the Ethernet hub. 
         [0039]    As can be appreciated, the Ethernet hub  500  as depicted in  FIG. 5  provides a distinct advantage that the Ethernet hub  500  can be used as an inline packet sniffing device for sniff packets on either a copper connection or an optical connection and the configuration of inline ports from two copper network ports or two optical network ports is automated without the need for a more complicated user command interface like those managed Ethernet switches. 
         [0040]    In accordance with another embodiment of the present invention, the Ethernet hub  500  in  FIG. 5  is replaced with an Ethernet switch with least five network ports which includes three copper network ports  510 ,  520  and  530  and two optical network ports  540  and  550 . The Ethernet switch  500  detects the presence status of the pluggable optical transceiver module  555  on one selected optical network port  550 . If the optical transceiver module  555  is connected on the selected optical network port  550 , the selected optical port  550  is configured as the “mirroring from” port and the ingress and egress data packets of the “mirroring from” port network  550  are forwarded (mirrored) to at least one monitor (“mirrored to”) port that is selected from the other network ports ( 510 ,  520 ,  530 ,  540 ) not including the “mirroring from” port  550 . If the pluggable optical transceiver module  555  is not connected on the selected optical network port  550 , a prescribed copper network port is configured as the “mirroring from” port and the ingress and egress data packets of the “mirroring from” port are forwarded (mirrored) to at least one monitor (“mirrored to”) port that is selected from the other network ports not including the prescribed “mirroring from” port. Such an embodiment of the present invention enables the Ethernet switch  500  to support a port mirroring functionality in which the selection of the “mirroring from” port from either a prescribed copper network port or a prescribed optical network port is automated without the need for a more complicated user command interface like those managed Ethernet switches. 
         [0041]      FIG. 6  is a detailed circuit schematic view of generating the presence signal of a pluggable optical transceiver module in one selected optical port in the Ethernet hub or switch in  FIG. 5 . As shown in  FIG. 6 , the pluggable optical transceiver module  610  has a presence connector pin  620  and a ground connector pin  630  which are internally wired (electrically shorted) together; the optical port  640  has a corresponding presence connector pin  650  and a corresponding ground connector pin  660 ; the presence connector pin  650  is connected to an voltage rail  680  (e.g., +3.3V) via a pull-up resistor  670  (e.g., a 4K7 ohm resistor) and the ground connector pin  660  is connected to the ground  690 . When the optical transceiver module  610  is not engaged with the optical port  640 , the presence signal  695  is pulled up to the voltage level of the power rail  680 , representing a logic “High”, which indicates that the pluggable optical transceiver module  620  is not connected to the optical port  640 . When the pluggable optical transceiver module  610  is engaged with the optical port  640 , the corresponding presence connector pin  650  and the ground connector pin  660  on the optical port  640  are electrically connected with the presence connector pin  620  and the ground connector pin  630  on the pluggable optical fiber module  610 , which will pull down the presence signal  695  to the voltage level of the ground  690 , representing a logic “Low”, which indicates the pluggable optical transceiver module  610  is being connected on the optical port  610 . 
         [0042]    Although the present invention has been described in terms of various embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art after reading the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all changes and modifications as fall within the true spirit and scope of the invention. As a result, the invention is not limited to the specific examples and illustrations discussed above, but only the following claims and their equivalents.