7 The load balancer plugin is currently in *beta* version. Both CLIs and
8 APIs are subject to *heavy* changes, which also means feedback is really
9 welcome regarding features, apis, etc…
14 This plugin provides load balancing for VPP in a way that is largely
15 inspired from Google’s MagLev:
16 http://research.google.com/pubs/pub44824.html
18 The load balancer is configured with a set of Virtual IPs (VIP, which
19 can be prefixes), and for each VIP, with a set of Application Server
22 There are four encap types to steer traffic to different ASs: 1).
23 IPv4+GRE ad IPv6+GRE encap types: Traffic received for a given VIP (or
24 VIP prefix) is tunneled using GRE towards the different ASs in a way
25 that (tries to) ensure that a given session will always be tunneled to
28 2). IPv4+L3DSR encap types: L3DSR is used to overcome Layer 2
29 limitations of Direct Server Return Load Balancing. It maps VIP to DSCP
30 bits, and reuse TOS bits to transfer DSCP bits to server, and then
31 server will get VIP from DSCP-to-VIP mapping.
33 Both VIPs or ASs can be IPv4 or IPv6, but for a given VIP, all ASs must
34 be using the same encap. type (i.e. IPv4+GRE or IPv6+GRE or IPv4+L3DSR).
35 Meaning that for a given VIP, all AS addresses must be of the same
38 3). IPv4/IPv6 + NAT4/NAT6 encap types: This type provides kube-proxy
39 data plane on user space, which is used to replace linux kernel’s
40 kube-proxy based on iptables.
42 Currently, load balancer plugin supports three service types: a) Cluster
43 IP plus Port: support any protocols, including TCP, UDP. b) Node IP plus
44 Node Port: currently only support UDP. c) External Load Balancer.
46 For Cluster IP plus Port case: kube-proxy is configured with a set of
47 Virtual IPs (VIP, which can be prefixes), and for each VIP, with a set
48 of AS addresses (ASs).
50 For a specific session received for a given VIP (or VIP prefix), first
51 packet selects a AS according to internal load balancing algorithm, then
52 does DNAT operation and sent to chosen AS. At the same time, will create
53 a session entry to store AS chosen result. Following packets for that
54 session will look up session table first, which ensures that a given
55 session will always be routed to the same AS.
57 For returned packet from AS, it will do SNAT operation and sent out.
59 Please refer to below for details:
60 https://schd.ws/hosted_files/ossna2017/1e/VPP_K8S_GTPU_OSSNA.pdf
65 The load balancer has been tested up to 1 millions flows and still
66 forwards more than 3Mpps per core in such circumstances. Although 3Mpps
67 seems already good, it is likely that performance will be improved in
76 The load balancer needs to be configured with some parameters:
80 lb conf [ip4-src-address <addr>] [ip6-src-address <addr>]
81 [buckets <n>] [timeout <s>]
83 ip4-src-address: the source address used to send encap. packets using
84 IPv4 for GRE4 mode. or Node IP4 address for NAT4 mode.
86 ip6-src-address: the source address used to send encap. packets using
87 IPv6 for GRE6 mode. or Node IP6 address for NAT6 mode.
89 buckets: the *per-thread* established-connections-table number of
92 timeout: the number of seconds a connection will remain in the
93 established-connections-table while no packet for this flow is received.
100 lb vip <prefix> [encap (gre6|gre4|l3dsr|nat4|nat6)] \
101 [dscp <n>] [port <n> target_port <n> node_port <n>] [new_len <n>] [del]
103 new_len is the size of the new-connection-table. It should be 1 or 2
104 orders of magnitude bigger than the number of ASs for the VIP in order
105 to ensure a good load balancing. Encap l3dsr and dscp is used to map VIP
106 to dscp bit and rewrite DSCP bit in packets. So the selected server
107 could get VIP from DSCP bit in this packet and perform DSR. Encap
108 nat4/nat6 and port/target_port/node_port is used to do kube-proxy data
115 lb vip 2002::/16 encap gre6 new_len 1024
116 lb vip 2003::/16 encap gre4 new_len 2048
117 lb vip 80.0.0.0/8 encap gre6 new_len 16
118 lb vip 90.0.0.0/8 encap gre4 new_len 1024
119 lb vip 100.0.0.0/8 encap l3dsr dscp 2 new_len 32
120 lb vip 90.1.2.1/32 encap nat4 port 3306 target_port 3307 node_port 30964 new_len 1024
121 lb vip 2004::/16 encap nat6 port 6306 target_port 6307 node_port 30966 new_len 1024
123 Configure the ASs (for each VIP)
124 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
128 lb as <vip-prefix> [<address> [<address> [...]]] [del]
130 You can add (or delete) as many ASs at a time (for a single VIP). Note
131 that the AS address family must correspond to the VIP encap. IP family.
137 lb as 2002::/16 2001::2 2001::3 2001::4
138 lb as 2003::/16 10.0.0.1 10.0.0.2
139 lb as 80.0.0.0/8 2001::2
140 lb as 90.0.0.0/8 10.0.0.1
147 lb set interface nat4 in <intfc> [del]
149 Set SNAT feature in a specific interface. (applicable in NAT4 mode only)
153 lb set interface nat6 in <intfc> [del]
155 Set SNAT feature in a specific interface. (applicable in NAT6 mode only)
160 The plugin provides quite a bunch of counters and information. These are
161 still subject to quite significant changes.
177 MagLev is a distributed system which pseudo-randomly generates a
178 new-connections-table based on AS names such that each server configured
179 with the same set of ASs ends up with the same table. Connection
180 stickiness is then ensured with an established-connections-table. Using
181 ECMP, it is assumed (but not relied on) that servers will mostly receive
182 traffic for different flows.
184 This implementation pushes the parallelism a little bit further by using
185 one established-connections table per thread. This is equivalent to
186 assuming that RSS will make a job similar to ECMP, and is pretty useful
187 as threads don’t need to get a lock in order to write in the table.
192 A load balancer requires an efficient read and write hash table. The
193 hash table used by ip6-forward is very read-efficient, but not so much
194 for writing. In addition, it is not a big deal if writing into the hash
195 table fails (again, MagLev uses a flow table but does not heavily
198 The plugin therefore uses a very specific (and stupid) hash table. -
199 Fixed (and power of 2) number of buckets (configured at runtime) - Fixed
200 (and power of 2) elements per buckets (configured at compilation time)
205 When an AS is removed, there is two possible ways to react. - Keep using
206 the AS for established connections - Change AS for established
207 connections (likely to cause error for TCP)
209 In the first case, although an AS is removed from the configuration, its
210 associated state needs to stay around as long as it is used by at least
213 In order to avoid locks, a specific reference counter is used. The
214 design is quite similar to clib counters but: - It is possible to
215 decrease the value - Summing will not zero the per-thread counters -
216 Only the thread can reallocate its own counters vector (to avoid
219 This reference counter is lock free, but reading a count of 0 does not
220 mean the value can be freed unless it is ensured by *other* means that
221 no other thread is concurrently referencing the object. In the case of
222 this plugin, it is assumed that no concurrent event will take place