Enhanced sFlow
This section is applicable for the following families of devices:
a Falcon
a AlleyCat5P
a AlleyCat5X
At times, it is useful for the controller to obtain the original packet’s input/output port and the Ingress/Egress timestamp. The controller can then utilize this information to calculate
message forwarding delay, and draw the
forwarding delay jitter curve, thus provide information on network transmission quality.
For that purpose, enhanced sFlow packet format is defined. Enhanced sFlow format is a proprietary format based on standard sFlow v5.
Enhanced sFlow tunnel Layer4 encapsulation can
be either:
IPv4/UDP
IPv6/UDP
Enhanced sFlow Architecture
Due to Falcon HW, the enhanced sFlow solution requires one free loopback port through which the mirrored traffic is looped back to the device. The following figure illustrates the engaged components, and is followed by a description of data flow.
Figure 179: Enhanced sFlow Components and Data Flow
The first path (light-blue arrows):
Egress mirroring is enabled on Sample port X by EPCL. An EPCL rule matches the packet, assigns it any of the target analyzer IDs (1-7), and triggers a PHA thread to save target information into the copy-reserved descriptor field.
The Egress Replication Engine (EREP) duplicates packet descriptor, and assigns the mirrored packet to the target analyzer ID configured by EPCL. Then, the pre-Egress engine (EQ) maps the target analyzer ID to Analyzer port (loopback port Y).
A second EPCL rule matches the mirrored packet, and binds it to a second PHA thread.
This second PHA thread adds an sFlow header prefixing the mirrored packet; this header incorporate most of the header fields except those of the tunnel header.
PTP TSU (TimeStamping Unit) adds a Tx timestamp to the sFlow header.
Port Y is set as a loopback port.
The second path (blue arrows):
Once packet is looped back to pipeline, a Private VLAN Edge (PVE), or an IPCL rule, matches the looped back traffic, and assigns a target ePort with a Tunnel start attribute. The ePort to Physical port (E2PHY) maps the target ePort to an output port, from which it is streamed to a Collector unit.
A third EPCL rule matches the looped back traffic, and binds it to a third PHA thread, which sets the tunnel start field in the sFlow header.
CPSS Implementation Considerations
The application is responsible for setting the following CPSS parameters:
Sampling Port, formatted as dev_id/port_num, and sampling rate 1:N
Target analyzer ID: ranged 1-7
Target ePort
number for Tunnel start
Analyzer port
number – loopback port Y in illustration
Tunnel Start (TS) entry pointer
Physical Analyzer port, formatted as dev_id/port_num, connected to the Collector unit – output port A in illustration
Analyzer Node IP address – 32bits representing dev_id, and used for setting IP_High and IP_Low fields
In addition, the application needs to configure the following components:
Table 113: Component Configuration by Application
Component Configuration per Steps
Mirror engine
Set MIRROR to analyzer port
Set ratio to 1:N rate
Set analyzed ePort to loopback port Y
ePort for Tunnel start
Set target ePort with tunnel start attributes; for example, UDP over IPv4 Tunnel
Implement 2 tunnel configuration APIs—DMAC, SMAC, DIP, SIP, Dport, and Sport
API for setting Tunnel Start entry pointer parameter
A call of type <customer-prefix>sflowTunnelStartSet (TSentry* TSentryPointer)
API for setting tunnel configuration, and mapping target ePort to an output port A connected to a collector unit; pass DMAC, SMAC, DIP, SIP, Dport, and Sport as parameter
A call of type EtoPHY
Assign tunnel start ePort to looped back traffic by one of two methods
Method 1: Use PVE
Enable PVE
Set Bridge Global configuration0 register to <PVLAN Enable> (bit 14 in register)
Enable ePort for PVE
Set Ingress bridge ePort for loopback port Y to <PortPVLANEn>
Set destination port for the set PVE port Y
Set physical Analyzer output port A connected to collector unit at the Ingress bridge ePort table to <PortPVLANTrgEport>/
<PortPVLANTrgDev>
Method2: Use an IPCL rule
Match looped back traffic, and assign the collector unit ePort. This ePort attribute acts as tunnel start, with:
Key:
UDB Metadata <source port > = loopback port Y
Packet first word (32bit) = 0x5 (sflow version)
Action:
<redirect command> = target Egress interface
Target egress interface = ePort (output port A connected to collector)
EPCL rules
First EPCL rule
Enable Egress mirroring, and trigger the first PHA thread THR61_save_target_port_info with:
Key:
UDB Metadata <source port> = sample port
Action:
<Egress Mirror to Analyzer> = Target analyzer ID //binds to an analyzer ID assigned by User
<Egress Mirror mode> = Egress Mirror packet not DROPPED
<PHA Thread
Number Assignment Enable> = 1
<PHA Thread
number> = THR61_save_target_port_info
Second EPCL rule
NOTE: The second EPCL rule priority must
be higher than that of the first one
Match mirrored traffic, and trigger the second PHA thread THR66_enhanced_sFlow
Key:
UDB Metadata <Egress Mtag Cmd> = TO_ANALYZER
UDB Metadata <Analyzer Target ePort> = Analyzer port
number (loopback port Y)
Action:
Disable OAM engine by <OAM Processing En> = 0. PHA counts Packet
number with flow ID as index
Use analyzer ID as flow index by <Flow-ID> = Target analyzer ID.
Flow index is used by second PHA thread THR66_enhanced_sFlow
<PHA Thread
Number Assignment Enable> = 1
<PHA Thread
number> = THR66_enhanced_sFlow
Third EPCL rule
Match looped back traffic, and trigger third PHA thread THR62_enhanced_sFlow_fill_remain_IPv4 or THR63_enhanced_sFlow_fill_remain_IPv6
Key:
UDB Metadata <source port> = loopback port Y
Action:
<PHA Thread
Number Assignment Enable> = 1
<PHA Thread
number> = THR62_enhanced_sFlow_fill_remain_IPv4 or THR63_enhanced_sFlow_fill_remain_IPv6
<PHA metadata assignment enable> = True
Pass node IP address to PHA to enable adding of sflow header by third PHA thread <metadata[31:0]> = Analyzer Node IP address[31:0]
PHA Firmware Description
First PHA thread – THR61_save_target_port_info
Save target port information into the copy reserved field.
Second PHA thread – THR66_enhanced_sFlow
FW adds sFlow header. Since TS is moved to the next path after the loopback, currently no need to split for ipv4/ipv6.
Third PHA thread – THR62_enhanced_sFlow_fill_remain_IPv4 or THR63_enhanced_sFlow_fill_remain_IPv6
FW adds remainder of sFlow field relative to tunnel start. Since TS uses IPv4/IPv6 encapsulation, this thread is split into IPv4 and IPv6.
Table 114: PHA Thread Implementation by Application
Thread
Steps
THR61_save_target_port_info
Save target port information into the copy reserved field
THR66_enhanced_sFlow
Insert sFlow header
before the mirrored packet
Set sFlow header
Enable PTP TSU
THR62_enhanced_sFlow_fill_remain_IPv4
After loopback, traffic reenters pipeline, and Tunnel Start wraps sFlow header with IPv4 encapsulation.
sFlow header offset is 44 bytes:
L3 anchor + 20 Bytes for IP header + 8 Bytes for UDP header
Update UDP and IP length and checksum
THR63_enhanced_sFlow_fill_remain_IPv6
Same as IPv4 except Tunnel Start uses IPv6 encapsulation
sFlow header offset changes according to IPv6
Update UDP and checksum 该过程IPCL和EPCL优先级有什么要求
在编程中，尝试向不处理特定消息的对象发送消息会导致错误。然而，在宣布错误之前，运行时系统会给予接收对象第二次处理该消息的机会。
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