Flow-Based Hashing For Ecmp - Dell S4048T Configuration Manual

mac-in-mac header based hashing is disabled
TcpUdp Load Balancing
Dell(conf)#
• Packet Header parameters for the first portion of the RTAG7 hash can be controlled. By default, all the
listed parameters from the Packet header are considered for hash computation. Few parameters [on
demand] can be removed using the given CLIs.
Dell(conf)#load-balance ?
flexhash
ingress-port
ip-selection
computation(default = source-ip dest-ip vlan protocol L4-source-port L4-dest-
port)
ipv6-selection
computation(default = source-ipv6 dest-ipv6 vlan protocol L4-source-port L4-
dest-port)
mac
computation(default = source-mac dest-mac vlan ethertype)
tcp-udp
hashing
tunnel
computation(default = Hash-computation based on Inner Header)]
• The second portion comes from static physical configuration such as ingress and egress port numbers.
• RTAG7 hashing also provides options to select between multiple hash algorithms that would result in
balanced traffic distribution for various traffic patterns.
Dell(conf)#hash-algorithm ecmp ?
crc16
crc16cc
crc32LSB
crc32MSB
crc-upper
flow-based-hashing
dest-ip
lsb
xor1
and lower 8 bits of xor1
xor2
and lower 8 bits of xor2
xor4
and lower 8 bits of xor4
xor8
and lower 8 bits of xor8
xor16

Flow-based Hashing for ECMP

Flow-based hashing is one of RTAG7 hashing techniques to cater to ECMP routing in multi-tier networks. It
addresses traffic polarization issues by ensuring proper flow distribution between ECMP members in the
higher layers of a multi-tier network. It facilitates a dynamic hash function selection across different nodes in
the network on a macro flow basis, by reducing route starvation and the unfair distribution of bandwidth
between members.
Polarization
Multipath routing is a method that is often used to address data forwarding issues during network failures so
that the network traffic reaches its desired destination. Multipath routing in IP networks is typically
implemented using Equal-Cost Multipath (ECMP) routing, which employs load balancing algorithms to
Enabled
Enable flexhash based on IP Protocol
Option to Source Port Id for ECMP/LAG hashing
Set the IPV4 key fields to use in hash
Set the IPV6 key fields to use in hash
Set the mac key fields to use in hash
Option to use TCP/UDP ports in packet for ECMP/LAG
Set the tunnel key fields to use in hash
CRC16_BISYNC - 16 bit CRC16-bisync polynomial
CRC16_CCITT - 16 bit CRC16 using CRC16-CCITT polynomial
CRC32_LOWER - LSB 16 bits of computed CRC32
CRC32_UPPER - MSB 16 bits of computed CRC32(default)
Use Upper 32 bits of key for hash computation
Enable flow based hashing
Use Destination IP for ECMP hashing
Always return the LSB of the key as the hash
CRC16_BISYNC_AND_XOR1 - Upper 8 bits of CRC16-BISYNC
CRC16_BISYNC_AND_XOR2 - Upper 8 bits of CRC16-BISYNC
CRC16_BISYNC_AND_XOR4 - Upper 8 bits of CRC16-BISYNC
CRC16_BISYNC_AND_XOR8 - Upper 8 bits of CRC16-BISYNC
CR16 - 16 bit XOR]
Equal Cost Multi-Path (ECMP) 373