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Server Assisted TRILL Edge

Server Assisted TRILL Edge. Linda Dunbar (ldunbar@huawei.com). Characteristics of Internet/Cloud Data Center. Large number of hosts Especially in data centers with virtualized servers (VMs).

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Server Assisted TRILL Edge

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  1. Server Assisted TRILL Edge Linda Dunbar (ldunbar@huawei.com)

  2. Characteristics of Internet/Cloud Data Center • Large number of hosts • Especially in data centers with virtualized servers (VMs). • Resource (energy, bandwidth, etc) efficient algorithms emphasizes on minimizing the number of physical servers and switches for all the VMs, • This criteria may lead to hosts belonging to same subnet to be placed under different locations (racks or rows).

  3. A B C D When one subnet spans across multiple locations and multiple subnets on one shelf: • Broadcast messages of each subnet will traverse links and switches in the backbone (which involves much more links and switches). • The Access switch need to learn all the MACs among all VLANs enabled on the ports. • E.g. One data centers has 80 rows, each row has 8 racks, each rack has 40 servers =>27200 servers. • Suppose each server is virtualized to 20 VMs. Then each TOR switch will have 20*40 = 800 VMs. If they belong to 80 different VLANs and each VLAN has 200 hosts, then the TOR switch has handle 80*200=16000 MAC&VLAN entries. • Even though switch is only supposed to learn the entries which communicate with hosts underneath, the frequent ARP/ND from all hosts within each subnet will always refresh the switch’s FDB. TRILL domain TOR switches performing TRILL encapsulation Page 3

  4. Impact to TRILL by massive amount of hosts • If TRILL boundary starts closer to servers, the number of MAC&VLAN entries to be learned by the TRILL edge is limited by the number of hosts belonging to all VLANs enabled on the TRILL edge port. • if the TRILL encapsulation starts at the Ingress port of Access switch (i.e. TOR switch), there are 5 different VLANs enabled on the port (i.e. VMs in one server belongs to 5 different VLANs), and each VLAN has 200 hosts, then TRILL Edge port has to learn 5*200=1000 MAC&VLAN entries. • But, there will be 27000 nodes in TRILL routing domain in the data center example. • If TRILL boundary starts at End of Row switches, the number of nodes in TRILL routing domain is limited by the number of ports of all End of Row switches. • In the DC example, 40 servers in a Rack and 8 Racks in a row, Assuming 20 VMs per Server, there are 40*8*20 = 6400 hosts to each End of Row switch. If all those hosts belong to 640 VLANs and each VLAN has 200 hosts  total number of MAC&VLAN entries to be learned by the TRILL edge = 640*200=128000.

  5. Special properties of Data Center network • VMs to server assignment is done by Server Manager, not random. • Topology is based on racks, rows. • There are massive number of hosts, but very small number of switches.

  6. Directory Server Assisted Edge • Directory Server, being connected with VM-manager, is aware of the location of the target VMs. • Directory Server can assist TRILL edge by various ways, e.g. • Server sends MAC&VLAN <-> TRILL edge mapping to TRILL edge node, • TRILL ingress node re-directs all ARP/ND to Directory Serverand get the MAC&VLAN <-> TRILL edge mapping as reply, or • Others • Benefits: • Utilize the unique characteristics of Data Center networks • Reduce flooding within TRILL domain • Reduce the amount of MAC&VLAN <-> TRILL edge mapping learnt by TRILL edge.

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