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diff --git a/docs/content/methodology/network_address_translation.md b/docs/content/methodology/network_address_translation.md new file mode 100644 index 0000000000..a46ea9af30 --- /dev/null +++ b/docs/content/methodology/network_address_translation.md @@ -0,0 +1,446 @@ +--- +bookToc: false +title: "Network Address Translation" +weight: 7 +--- + +# Network Address Translation + +## NAT44 Prefix Bindings + +NAT44 prefix bindings should be representative to target applications, +where a number of private IPv4 addresses from the range defined by +RFC1918 is mapped to a smaller set of public IPv4 addresses from the +public range. + +Following quantities are used to describe inside to outside IP address +and port bindings scenarios: + +- Inside-addresses, number of inside source addresses + (representing inside hosts). +- Ports-per-inside-address, number of TCP/UDP source + ports per inside source address. +- Outside-addresses, number of outside (public) source addresses + allocated to NAT44. +- Ports-per-outside-address, number of TCP/UDP source + ports per outside source address. The maximal number of + ports-per-outside-address usable for NAT is 64 512 + (in non-reserved port range 1024-65535, RFC4787). +- Sharing-ratio, equal to inside-addresses divided by outside-addresses. + +CSIT NAT44 tests are designed to take into account the maximum number of +ports (sessions) required per inside host (inside-address) and at the +same time to maximize the use of outside-address range by using all +available outside ports. With this in mind, the following scheme of +NAT44 sharing ratios has been devised for use in CSIT: + + **ports-per-inside-address** | **sharing-ratio** +-----------------------------:|------------------: + 63 | 1024 + 126 | 512 + 252 | 256 + 504 | 128 + +Initial CSIT NAT44 tests, including associated TG/TRex traffic profiles, +are based on ports-per-inside-address set to 63 and the sharing ratio of +1024. This approach is currently used for all NAT44 tests including +NAT44det (NAT44 deterministic used for Carrier Grade NAT applications) +and NAT44ed (Endpoint Dependent). + +Private address ranges to be used in tests: + +- 192.168.0.0 - 192.168.255.255 (192.168/16 prefix) + + - Total of 2^16 (65 536) of usable IPv4 addresses. + - Used in tests for up to 65 536 inside addresses (inside hosts). + +- 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) + + - Total of 2^20 (1 048 576) of usable IPv4 addresses. + - Used in tests for up to 1 048 576 inside addresses (inside hosts). + +### NAT44 Session Scale + +NAT44 session scale tested is govern by the following logic: + +- Number of inside-addresses(hosts) H[i] = (H[i-1] x 2^2) with H(0)=1 024, + i = 1,2,3, ... + + - H[i] = 1 024, 4 096, 16 384, 65 536, 262 144, ... + +- Number of sessions S[i] = H[i] * ports-per-inside-address + + - ports-per-inside-address = 63 + + **i** | **hosts** | **sessions** +------:|----------:|-------------: + 0 | 1 024 | 64 512 + 1 | 4 096 | 258 048 + 2 | 16 384 | 1 032 192 + 3 | 65 536 | 4 128 768 + 4 | 262 144 | 16 515 072 + +### NAT44 Deterministic + +NAT44det performance tests are using TRex STL (Stateless) API and traffic +profiles, similar to all other stateless packet forwarding tests like +ip4, ip6 and l2, sending UDP packets in both directions +inside-to-outside and outside-to-inside. + +The inside-to-outside traffic uses single destination address (20.0.0.0) +and port (1024). +The inside-to-outside traffic covers whole inside address and port range, +the outside-to-inside traffic covers whole outside address and port range. + +NAT44det translation entries are created during the ramp-up phase, +followed by verification that all entries are present, +before proceeding to the main measurements of the test. +This ensures session setup does not impact the forwarding performance test. + +Associated CSIT test cases use the following naming scheme to indicate +NAT44det scenario tested: + +- ethip4udp-nat44det-h{H}-p{P}-s{S}-[mrr|ndrpdr|soak] + + - {H}, number of inside hosts, H = 1024, 4096, 16384, 65536, 262144. + - {P}, number of ports per inside host, P = 63. + - {S}, number of sessions, S = 64512, 258048, 1032192, 4128768, + 16515072. + - [mrr|ndrpdr|soak], MRR, NDRPDR or SOAK test. + +### NAT44 Endpoint-Dependent + +In order to excercise NAT44ed ability to translate based on both +source and destination address and port, the inside-to-outside traffic +varies also destination address and port. Destination port is the same +as source port, destination address has the same offset as the source address, +but applied to different subnet (starting with 20.0.0.0). + +As the mapping is not deterministic (for security reasons), +we cannot easily use stateless bidirectional traffic profiles. +Inside address and port range is fully covered, +but we do not know which outside-to-inside source address and port to use +to hit an open session. + +Therefore, NAT44ed is benchmarked using following methodologies: + +- Unidirectional throughput using *stateless* traffic profile. +- Connections-per-second (CPS) using *stateful* traffic profile. +- Bidirectional throughput (TPUT, see below) using *stateful* traffic profile. + +Unidirectional NAT44ed throughput tests are using TRex STL (Stateless) +APIs and traffic profiles, but with packets sent only in +inside-to-outside direction. +Similarly to NAT44det, NAT44ed unidirectional throughput tests include +a ramp-up phase to establish and verify the presence of required NAT44ed +binding entries. As the sessions have finite duration, the test code +keeps inserting ramp-up trials during the search, if it detects a risk +of sessions timing out. Any zero loss trial visits all sessions, +so it acts also as a ramp-up. + +Stateful NAT44ed tests are using TRex ASTF (Advanced Stateful) APIs and +traffic profiles, with packets sent in both directions. Tests are run +with both UDP and TCP sessions. +As NAT44ed CPS (connections-per-second) stateful tests +measure (also) session opening performance, +they use state reset instead of ramp-up trial. +NAT44ed TPUT (bidirectional throughput) tests prepend ramp-up trials +as in the unidirectional tests, +so the test results describe performance without translation entry +creation overhead. + +Associated CSIT test cases use the following naming scheme to indicate +NAT44det case tested: + +- Stateless: ethip4udp-nat44ed-h{H}-p{P}-s{S}-udir-[mrr|ndrpdr|soak] + + - {H}, number of inside hosts, H = 1024, 4096, 16384, 65536, 262144. + - {P}, number of ports per inside host, P = 63. + - {S}, number of sessions, S = 64512, 258048, 1032192, 4128768, + 16515072. + - udir-[mrr|ndrpdr|soak], unidirectional stateless tests MRR, NDRPDR + or SOAK. + +- Stateful: ethip4[udp|tcp]-nat44ed-h{H}-p{P}-s{S}-[cps|tput]-[mrr|ndrpdr|soak] + + - [udp|tcp], UDP or TCP sessions + - {H}, number of inside hosts, H = 1024, 4096, 16384, 65536, 262144. + - {P}, number of ports per inside host, P = 63. + - {S}, number of sessions, S = 64512, 258048, 1032192, 4128768, + 16515072. + - [cps|tput], connections-per-second session establishment rate or + packets-per-second average rate, or packets-per-second rate + without session establishment. + - [mrr|ndrpdr|soak], bidirectional stateful tests MRR, NDRPDR, or SOAK. + +## Stateful traffic profiles + +There are several important details which distinguish ASTF profiles +from stateless profiles. + +### General considerations + +#### Protocols + +ASTF profiles are limited to either UDP or TCP protocol. + +#### Programs + +Each template in the profile defines two "programs", one for the client side +and one for the server side. + +Each program specifies when that side has to wait until enough data is received +(counted in packets for UDP and in bytes for TCP) +and when to send additional data. Together, the two programs +define a single transaction. Due to packet loss, transaction may take longer, +use more packets (retransmission) or never finish in its entirety. + +#### Instances + +A client instance is created according to TPS parameter for the trial, +and sends the first packet of the transaction (in some cases more packets). +Each client instance uses a different source address (see sequencing below) +and some source port. The destination address also comes from a range, +but destination port has to be constant for a given program. + +TRex uses an opaque way to chose source ports, but as session counting shows, +next client with the same source address uses a different source port. + +Server instance is created when the first packet arrives to the server side. +Source address and port of the first packet are used as destination address +and port for the server responses. This is the ability we need +when outside surface is not predictable. + +When a program reaches its end, the instance is deleted. +This creates possible issues with server instances. If the server instance +does not read all the data client has sent, late data packets +can cause a second copy of server instance to be created, +which breaks assumptions on how many packet a transaction should have. + +The need for server instances to read all the data reduces the overall +bandwidth TRex is able to create in ASTF mode. + +Note that client instances are not created on packets, +so it is safe to end client program without reading all server data +(unless the definition of transaction success requires that). + +#### Sequencing + +ASTF profiles offer two modes for choosing source and destination IP addresses +for client programs: seqential and pseudorandom. +In current tests we are using sequential addressing only (if destination +address varies at all). + +For client destination UDP/TCP port, we use a single constant value. +(TRex can support multiple program pairs in the same traffic profile, +distinguished by the port number.) + +#### Transaction overlap + +If a transaction takes longer to finish, compared to period implied by TPS, +TRex will have multiple client or server instances active at a time. + +During calibration testing we have found this increases CPU utilization, +and for high TPS it can lead to TRex's Rx or Tx buffers becoming full. +This generally leads to duration stretching, and/or packet loss on TRex. + +Currently used transactions were chosen to be short, so risk of bad behavior +is decreased. But in MRR tests, where load is computed based on NIC ability, +not TRex ability, anomalous behavior is still possible +(e.g. MRR values being way lower than NDR). + +#### Delays + +TRex supports adding constant delays to ASTF programs. +This can be useful, for example if we want to separate connection establishment +from data transfer. + +But as TRex tracks delayed instances as active, this still results +in higher CPU utilization and reduced performance issues +(as other overlaping transactions). So the current tests do not use any delays. + +#### Keepalives + +Both UDP and TCP protocol implementations in TRex programs support keepalive +duration. That means there is a configurable period of keepalive time, +and TRex sends keepalive packets automatically (outside the program) +for the time the program is active (started, not ended yet) +but not sending any packets. + +For TCP this is generally not a big deal, as the other side usually +retransmits faster. But for UDP it means a packet loss may leave +the receiving program running. + +In order to avoid keepalive packets, keepalive value is set to a high number. +Here, "high number" means that even at maximum scale and minimum TPS, +there are still no keepalive packets sent within the corresponding +(computed) trial duration. This number is kept the same also for +smaller scale traffic profiles, to simplify maintenance. + +#### Transaction success + +The transaction is considered successful at Layer-7 (L7) level +when both program instances close. At this point, various L7 counters +(unofficial name) are updated on TRex. + +We found that proper close and L7 counter update can be CPU intensive, +whereas lower-level counters (ipackets, opackets) called L2 counters +can keep up with higher loads. + +For some tests, we do not need to confirm the whole transaction was successful. +CPS (connections per second) tests are a typical example. +We care only for NAT44ed creating a session (needs one packet +in inside-to-outside direction per session) and being able to use it +(needs one packet in outside-to-inside direction). + +Similarly in TPUT tests (packet throuput, counting both control +and data packets), we care about NAT44ed ability to forward packets, +we do not care whether aplications (TRex) can fully process them at that rate. + +Therefore each type of tests has its own formula (usually just one counter +already provided by TRex) to count "successful enough" transactions +and attempted transactions. Currently, all tests relying on L7 counters +use size-limited profiles, so they know what the count of attempted +transactions should be, but due to duration stretching +TRex might have been unable to send that many packets. +For search purposes, unattempted transactions are treated the same +as attempted but failed transactions. + +Sometimes even the number of transactions as tracked by search algorithm +does not match the transactions as defined by ASTF programs. +See TCP TPUT profile below. + +### UDP CPS + +This profile uses a minimalistic transaction to verify NAT44ed session has been +created and it allows outside-to-inside traffic. + +Client instance sends one packet and ends. +Server instance sends one packet upon creation and ends. + +In principle, packet size is configurable, +but currently used tests apply only one value (100 bytes frame). + +Transaction counts as attempted when opackets counter increases on client side. +Transaction counts as successful when ipackets counter increases on client side. + +### TCP CPS + +This profile uses a minimalistic transaction to verify NAT44ed session has been +created and it allows outside-to-inside traffic. + +Client initiates TCP connection. Client waits until connection is confirmed +(by reading zero data bytes). Client ends. +Server accepts the connection. Server waits for indirect confirmation +from client (by waiting for client to initiate close). Server ends. + +Without packet loss, the whole transaction takes 7 packets to finish +(4 and 3 per direction). +From NAT44ed point of view, only the first two are needed to verify +the session got created. + +Packet size is not configurable, but currently used tests report +frame size as 64 bytes. + +Transaction counts as attempted when tcps_connattempt counter increases +on client side. +Transaction counts as successful when tcps_connects counter increases +on client side. + +### UDP TPUT + +This profile uses a small transaction of "request-response" type, +with several packets simulating data payload. + +Client sends 5 packets and closes immediately. +Server reads all 5 packets (needed to avoid late packets creating new +server instances), then sends 5 packets and closes. +The value 5 was chosen to mirror what TCP TPUT (see below) choses. + +Packet size is configurable, currently we have tests for 100, +1518 and 9000 bytes frame (to match size of TCP TPUT data frames, see below). + +As this is a packet oriented test, we do not track the whole +10 packet transaction. Similarly to stateless tests, we treat each packet +as a "transaction" for search algorthm packet loss ratio purposes. +Therefore a "transaction" is attempted when opacket counter on client +or server side is increased. Transaction is successful if ipacket counter +on client or server side is increased. + +If one of 5 client packets is lost, server instance will get stuck +in the reading phase. This probably decreases TRex performance, +but it leads to more stable results then alternatives. + +### TCP TPUT + +This profile uses a small transaction of "request-response" type, +with some data amount to be transferred both ways. + +In CSIT release 22.06, TRex behavior changed, so we needed to edit +the traffic profile. Let us describe the pre-22.06 profile first. + +Client connects, sends 5 data packets worth of data, +receives 5 data packets worth of data and closes its side of the connection. +Server accepts connection, reads 5 data packets worth of data, +sends 5 data packets worth of data and closes its side of the connection. +As usual in TCP, sending side waits for ACK from the receiving side +before proceeding with next step of its program. + +Server read is needed to avoid premature close and second server instance. +Client read is not stricly needed, but ACKs allow TRex to close +the server instance quickly, thus saving CPU and improving performance. + +The number 5 of data packets was chosen so TRex is able to send them +in a single burst, even with 9000 byte frame size (TRex has a hard limit +on initial window size). +That leads to 16 packets (9 of them in c2s direction) to be exchanged +if no loss occurs. +The size of data packets is controlled by the traffic profile setting +the appropriate maximum segment size. Due to TRex restrictions, +the minimal size for IPv4 data frame achievable by this method is 70 bytes, +which is more than our usual minimum of 64 bytes. +For that reason, the data frame sizes available for testing are 100 bytes +(that allows room for eventually adding IPv6 ASTF tests), +1518 bytes and 9000 bytes. There is no control over control packet sizes. + +Exactly as in UDP TPUT, ipackets and opackets counters are used for counting +"transactions" (in fact packets). + +If packet loss occurs, there can be large transaction overlap, even if most +ASTF programs finish eventually. This can lead to big duration stretching +and somehow uneven rate of packets sent. This makes it hard to interpret +MRR results (frequently MRR is below NDR for this reason), +but NDR and PDR results tend to be stable enough. + +In 22.06, the "ACK from the receiving side" behavior changed, +the receiving side started sending ACK sometimes +also before receiving the full set of 5 data packets. +If the previous profile is understood as a "single challenge, single response" +where challenge (and also response) is sent as a burst of 5 data packets, +the new profile uses "bursts" of 1 packet instead, but issues +the challenge-response part 5 times sequentially +(waiting for receiving the response before sending next challenge). +This new profile happens to have the same overall packet count +(when no re-transmissions are needed). +Although it is possibly more taxing for TRex CPU, +the results are comparable to the old traffic profile. + +## Ip4base tests + +Contrary to stateless traffic profiles, we do not have a simple limit +that would guarantee TRex is able to send traffic at specified load. +For that reason, we have added tests where "nat44ed" is replaced by "ip4base". +Instead of NAT44ed processing, the tests set minimalistic IPv4 routes, +so that packets are forwarded in both inside-to-outside and outside-to-inside +directions. + +The packets arrive to server end of TRex with different source address&port +than in NAT44ed tests (no translation to outside values is done with ip4base), +but those are not specified in the stateful traffic profiles. +The server end (as always) uses the received address&port as destination +for outside-to-inside traffic. Therefore the same stateful traffic profile +works for both NAT44ed and ip4base test (of the same scale). + +The NAT44ed results are displayed together with corresponding ip4base results. +If they are similar, TRex is probably the bottleneck. +If NAT44ed result is visibly smaller, it describes the real VPP performance. |