Gigabit switch with frame forwarding and address learning

• US 20020009081A1
• Filed: 06/11/2001
• Published: 01/24/2002
• Est. Priority Date: 06/09/2000
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Kalkunte, Mohan, Ambe, Shekhar, Kadambi, Shiri, Sampath, Srinivas
• Granted Patent: US 7,046,679 B2
• Time in Patent Office: Days
• US Class Current: 370/389
• CPC Class Codes: H04L 12/462 LAN interconnection over a bridge based backbone
• CPC Class Codes: H04L 45/00 Routing or path finding of packets in data switching networks routing or path finding in wireless networks H04W40/00
• CPC Class Codes: H04L 45/16 Multipoint routing
• CPC Class Codes: H04L 45/245 Link aggregation, e.g. trunking
• CPC Class Codes: H04L 45/52 Multiprotocol routers
• CPC Class Codes: H04L 45/742 Route cache; Operation thereof
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2458 Modification of priorities while in transit
• CPC Class Codes: H04L 47/266 Stopping or restarting the source, e.g. X-on or X-off
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04L 47/32 by discarding or delaying data units, e.g. packets or frames
• CPC Class Codes: H04L 49/102 using shared medium, e.g. bus or ring
• CPC Class Codes: H04L 49/109 Integrated on microchip, e.g. switch-on-chip
• CPC Class Codes: H04L 49/15 Interconnection of switching modules
• CPC Class Codes: H04L 49/3009 Header conversion, routing tables or routing tags
• CPC Class Codes: H04L 49/3018 Input queuing
• CPC Class Codes: H04L 49/3036 Shared queuing
• CPC Class Codes: H04L 49/351 for local area network [LAN], e.g. Ethernet switches
• CPC Class Codes: H04L 49/352 Gigabit ethernet switching [GBPS]
• CPC Class Codes: H04L 49/354 for supporting virtual local area networks [VLAN]
• CPC Class Codes: H04L 49/506 : Backpressure
• CPC Class Codes: H04L 49/508 : Head of Line Blocking Avoidance
• CPC Class Codes: H04L 49/602 : Multilayer or multiprotocol switching, e.g. IP switching
• CPC Class Codes: H04L 69/22 : Parsing or analysis of headers
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A network switch for network communications is disclosed. The switch includes a first data port interface supporting at least one data port transmitting and receiving data at a first data rate and a second data port interface supporting at least one data port transmitting and receiving data at a second data rate. The switch also has a CPU interface configured to communicate with a CPU and a memory management unit for communicating data from at least one of the first and second data port interfaces and a memory. It also includes a communication channel for communicating data and messaging information between the first and second data port interfaces and the memory management unit and a plurality of lookup tables, including an address resolution lookup table and a VLAN table. One of the first or second data port interfaces is configured to determine an egress ports or egress ports for an incoming data packet from a search of the address resolution lookup table and the VLAN table using a VLAN ID derived from the incoming data packet. Methods directed to forwarding data packet and learning absent addresses are also disclosed.

Claims

1. A network switch for network communications, said network switch comprising:

a first data port interface, said first data port interface supporting at least one data port transmitting and receiving data at a first data rate;

a second data port interface, said second data port interface supporting at least one data port transmitting and receiving data at a second data rate;

a CPU interface, said CPU interface configured to communicate with a CPU;

a memory management unit for communicating data from at least one of said first data port interface and said second data port interface and a memory;

a communication channel, said communication channel for communicating data and messaging information between said first data port interface, said second data port interface, and said memory management unit;

a plurality of lookup tables, said lookup tables including an address resolution lookup table and a VLAN table,

wherein one of said first data port interface and said second data port interface is configured to determine an egress port or egress ports, for an incoming data packet received by said one of said first data port interface and said second data port interface, from a search of said address resolution lookup table and said VLAN table using a VLAN ID derived from the incoming data packet.

2. A network switch as recited in claim 1, wherein the second data rate is greater than the first data rate, a header of the incoming data packet contains an opcode used to identify a packet type, the incoming data packet arrives at a port of the second data port interface, and the second data port interface is configured to forward the incoming packet based on the opcode.

3. A network switch as recited in claim 2, wherein said opcode identifies whether the incoming data packet is a unicast packet, a multicast packet, a broadcast packet or resulted in a destination lookup failure.

4. A method of switching data in a network switch, said method comprising:

receiving an incoming data packet at a first port of a switch;

reading a first packet portion, less than a full packet length, to determine particular packet information;

deriving a VLAN ID from said first packet portion;

searching a VLAN table using VLAN ID;

searching an address resolution lookup table using said particular packet information and the VLAN ID;

obtaining an egress port or egress ports based on the above searching steps;

determining whether there is a matched entry in the address resolution lookup table;

if said matched entry is not in the address resolution lookup, learning the particular packet information and placing the particular packet information as an entry in the address resolution lookup table;

modifying the incoming data packet to include forwarding and routing information based on the above searching steps; and

sending the modified data packet to the egress port or egress ports.

5. A method as recited in claim 4, wherein said step of deriving a VLAN ID from said first packet portion comprises the steps of:

reading the VLAN ID from a VLAN tag in a header of the incoming data packet, when the incoming data packet is tagged; and

searching a port based VLAN table based on the particular packet information to obtain the VLAN ID, when the incoming data packet is untagged.

6. A method as recited in claim 4, wherein when the incoming data packet is a multicast packet, said step of obtaining an egress port or egress ports comprises:

deriving a multicast index from a result from said step of searching the address resolution lookup table; and

searching a multicast table using the multicast index as a key to obtain the egress ports.

7. A method as recited in claim 4, wherein said step of obtaining an egress port or egress ports comprises obtaining a port bitmap, a module ID bitmap, an untagged port bitmap and a class of service.

8. A method as recited in claim 4, further comprising the steps of:

determining if the incoming data packet should be mirrored to another port;

determining if a destination for the incoming data packet is a trunked port; and

determining if a destination for the incoming data packet is on a stacked linked network switch connected to the network switch.

9. A network switch comprising:

at least a first port;

means for receiving an incoming data packet at the first port;

means for reading a first packet portion, less than a full packet length, to determine particular packet information;

means for deriving a VLAN ID from said first packet portion;

means for searching a VLAN table using VLAN ID;

means for searching an address resolution lookup table using said particular packet information and the VLAN ID;

means for obtaining an egress port or egress ports based on the above searching steps;

means for determining whether there is a matched entry in the address resolution lookup table;

means for learning the particular packet information and means for placing the particular packet information as an entry in the address resolution lookup table;

means for modifying the incoming data packet to include forwarding and routing information based on results of the above searching means; and

means for sending the modified data packet to the egress port or egress ports;

wherein when said matched entry is not in the address resolution lookup table, the means for learning the particular packet information and the means for placing the particular packet information are used to update the address resolution lookup table.

10. A network switch as recited in claim 9, wherein said means for deriving a VLAN ID from said first packet portion comprises:

means for reading the VLAN ID from a VLAN tag in a header of the incoming data packet, when the incoming data packet 13 tagged; and

means for searching a port based VLAN table based on the particular packet information to obtain the VLAN ID;

wherein the means for reading the VLAN ID supplies the VLAN ID when the incoming data packet is tagged and the means for searching a port based VLAN table supplies the VLAN ID when the incoming data packet is untagged.

11. A network switch as recited in claim 9, wherein when the incoming data packet is a multicast packet, said means for obtaining an egress port or egress ports comprises:

means for deriving a multicast index from a result from said step of searching the address resolution lookup table; and

means for searching a multicast table using the multicast index as a key to obtain the egress ports.

12. A network switch as recited in claim 9, wherein said means for obtaining an egress port or egress ports comprises means for obtaining a port bitmap, a module ID bitmap, an untagged port bitmap and a class of service.

13. A network switch as recited in claim 9, further comprising:

means for determining if the incoming data packet should be mirrored to another port;

means for determining if a destination for the incoming data packet is a trunked port; and

means for determining if a destination for the incoming data packet is on a stacked linked network switch connected to the network switch.