Method and apparatus for optimizing data traffic path through a stacked switch LAG configuration
View Patent ↗A stacked switch includes two or more individual network switches connected to each other in a ring or daisy chain topology over stacking links, and at least one port on two or more of the individual switches comprising the stacked switch is a member of a LAG configured on the stacked switch. Each of the individual switches comprising the stacked switch include control plane and data plane functionality that operates to maintain switching tables and to process network data ingressing to the switch to determine how to forward the network data through the switch to an egress point. The control functionality included in each of the switches comprising the stacked switch also includes an enhanced ECMP functionality that operates to optimize the use of stacking link bandwidth on the stacking links connecting the two or more individual switches to each other.
1. A method for forwarding network data through a stacked switch, comprising:
identifying a relative cost to forward network data from an ingress switch to each of a plurality of egress switches that are coupled together and to the ingress switch through stacking links, and storing the plurality of identified relative costs, wherein each identified relative cost represents a number of the stacking links over which network data ingressing to the ingress switch is forwarded before egressing the egress switch associated with that identified relative cost;
receiving network data on the ingress switch that includes the identity of a link aggregation group (LAG) associated with the stacked switch, performing a hashing operation on information included in the network data to calculate a next hop value that is associated with a first egress switch of the plurality of egress switches for forwarding the network data out of the stacked switch, wherein the first egress switch is associated with a first identified cost of the plurality of identified costs;
determining that the calculated next hop value maps to a LAG port that is not located on the ingress switch and, in response, calculating a reduced relative cost that corresponds to a second identified relative cost of the plurality of identified costs that is less than the first identified relative cost; and
transmitting the network data over a second egress switch of the plurality of egress switches that is associated with the second identified relative cost if an egress port on the second egress switch is a member of the LAG.
2. The method of claim 1 , wherein the performing the hash operation on information included in the network data to calculate the next hop value includes performing the hashing operation on information located in a header of a packet of the network data.
3. The method of claim 1 , wherein the transmitting the network data over the second egress switch associated with the second identified relative cost results in the network data being forwarded over fewer stacking links relative to transmitting the network data over the first egress switch associated with the first identified relative cost.
4. The method of claim 1 , wherein the reduced relative cost is calculated by subtracting a maximum value of the plurality of identified relative cost and a variable from the calculated next hop value.
5. The method of claim 4 , wherein the variable is an integer between zero and N.
6. The method of claim 1 , wherein the network data is transmitted on a third egress switch of the plurality of egress switches that is included in the stacked switch and that has a lower or a higher switch identity than the second egress switch if the second identified relative cost corresponds to the second egress switch and the third egress switch and the second egress switch does not include an egress port that is a member of the LAG.
7. The method of claim 6 , wherein the lower or the higher switch identity is an assigned identity.
8. The method of claim 1 , wherein the reduced relative cost is modified by incrementing or decrementing the reduced relative cost until an egress switch that includes an egress port that is a member of the LAG is identified.
9. The method of claim 1 , wherein the calculated next hop value is used to identify an egress switch for forwarding the network data if no egress switches associated with the second identified relative cost include an egress port that is a member of the LAG.
10. A stacked switch, comprising:
a plurality of separate switches, each switch connected to at least one other switch over a stacking link and each of the switches including means for storing and running an enhanced equal cost multipath functionality that operates to minimize the number of stacking links over which network data associated with a link aggregation group (LAG) is forwarded after ingressing to the stacked switch and before egressing from the stacked switch, wherein the enhanced equal cost multipath functionality operates to calculate a relative cost associated with forwarding the network data through the stacked switch, compare the calculated relative cost with a stored previously identified relative cost, calculate a reduced relative cost in response to a hashing operation on the network data providing a next hop value that maps to a LAG port that is not located on the switch that received the network data, and transmit the network data over an egress switch included in the stacked switch that corresponds to the calculated reduced relative cost if an egress port on the egress switch is member of the LAG.
11. The stacked switch of claim 10 , wherein the enhanced equal cost multipath functionality operates to calculate the reduced relative cost if the calculated relative cost is greater than the stored previously identified relative cost.
12. The stacked switch of claim 11 , wherein the previously identified relative cost corresponds to the number of stacking links over which the network data ingressing to an ingress switch is forwarded as a result of a hash value calculated on information included in the network data.
13. The stacked switch of claim 11 , wherein the calculated relative cost is the number of stacking links over which the network data ingressing to an ingress switch is forwarded as a result of a hash algorithm performed on information included in the network data.
14. The stacked switch of claim 11 , wherein the calculated reduced relative cost is calculated by subtracting a maximum value of the previously identified relative cost and a variable from the calculated relative cost.
15. The stacked switch of claim 14 , wherein the variable is an integer between zero and N.
16. The stacked switch of claim 11 , wherein the network data is transmitted on another egress switch included in the stacked switch with a lower or a higher switch identity if the calculated reduced relative cost corresponds to two egress switches included in the stacked switch and one of the two egress switches does not include an egress port that is a member of the LAG.
17. The stacked switch of claim 16 , wherein the lower or the higher switch identity is an assigned identity.
18. The stacked switch of claim 11 , wherein the calculated reduced relative cost is modified by incrementing or decrementing the calculated reduced relative cost until an egress switch that includes an egress port that is a member of the LAG is identified.
19. The stacked switch of claim 11 , wherein the calculated relative cost is used to identify an egress switch if no egress switches corresponding to the calculated reduced relative cost include an egress port that is a member of the LAG.