Sgt stands for security group tag of the monitored

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SGT stands for security group tag of the monitored frame, P field indicates that the ERSPAN payload is an Ethernet pro- tocol frame. FT,Frame Type, indicates whether the mirrored frame is a Ethernet 802.3 frame, or a IP packet. Hardware ID, Hw ID, is an unique identifier of an ERSPAN engine, Direction bit, D, indicates whether the original frame was SPAN’ed in ingress(0) or in egress(1). Finally, O indicates whether or not the optional platform-specific subheader is presented. Implementation: For type III, we introduced another two fields to kernel through netlink API; hardware ID and direction. The COS, BSO, and T fields can be extracted or inferred from the mirrored frame. Timestamp value is calculated by calling the kernel ktime get real() with 100 microseconds granularity. Currently we do not support other timer granularties. In addition, the SGT is hard-coded to 0, non-ethernet mirrored packet is not supported, so FT is always 0 and P is set to 1. There is no implementation of sub-headers, so O bit is 0. 3. Example Use Case We use Figure 3 as an example topology to demostrate the three configuration ways of ERSPAN. Assuming a network administrator wants to monitor a network consisting of 1) physical machines connected to Cisco switches, 2) virtual- ized Linux machine with multiple VMs deployed and vir- tual switch (openvswitch.ko) enforcing the fowarding poli- cies, and 3) non-virtualized Linux physical machines, e.g., service nodes in data center such as gateways. Assuming all the monitored servers are under IP network of 10 . 1 . 1 . * , and We place a traffic sniifer over another IP network of 192 . 168 . 1 . * . The following subsection describes the config- uration for each case. 3.1 Cisco Switch We use Nexus 5000 switch and configure its ERSPAN tunnel with session ID 10, remote IP pointing to the traffic sniffer, 192 . 168 . 1 . 1 , and local IP address as 192 . 168 . 1 . 2 . As a re-
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sult, both the ingress and egress traffic on ports 11 and 12 will be msdfirrored to the remote sniffer. monitor session 10 type erspan-source erspan-id 10 vrf default destination ip source interface Ethernet1/11 both source interface Ethernet1/12 both no shut monitor erspan origin ip-address global 3.2 Open vSwitch Kernel Module Open vSwitch consists of two components: a userspace dae- mon, called ovs-vswitchd, and a flow cache as a kernel mod- ule, called openvswitch.ko. While ovs-vswitchd talks to the OpenFlow controller and programs its OpenFlow flow ta- bles, the openvswitch.ko keeps a cache where the subsequent flows are handled inside the kernel space. The openvswitch.ko provides a user-facing netlink API that models a network bridge that connects multiple ports through a single table [9]. This example shows how to use the netlink API provided by openvswitch.ko module, with the utility, ovs-dpctl, to create a ERSPAN tunnel.
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  • Fall '19
  • IP address, ERSPAN, ERSPAN tunnel

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