IP Traffic Flow SecurityLabN Consulting, L.L.C.chopps@chopps.orgThis document describes a mechanism to enhance IPsec traffic flow
security by adding traffic flow confidentiality to encrypted IP
encapsulated traffic. Traffic flow confidentiality is provided by
obscuring the size and frequency of IP traffic using a fixed-sized,
constant-send-rate IPsec tunnel. The solution allows for congestion
control as well as non-constant send-rate usage.Traffic Analysis (, ) is the act of extracting
information about data being sent through a network. While one may
directly obscure the data through the use of encryption ,
the traffic pattern itself exposes information due to variations in
it's shape and timing (, ).
Hiding the size and frequency of traffic is referred to as Traffic
Flow Confidentiality (TFC) per . provides for TFC by allowing padding to be added to encrypted
IP packets and allowing for transmission of all-pad packets
(indicated using protocol 59). This method has the major limitation
that it can significantly under-utilize the available bandwidth.The IP-TFS solution provides for full TFC without the aforementioned
bandwidth limitation. This is accomplished by using a
constant-send-rate IPsec tunnel with fixed-sized
encapsulating packets; however, these fixed-sized packets can contain
partial, whole or multiple IP packets to maximize the bandwidth of
the tunnel. A non-constant send-rate is allowed, but the
confidentiality properties of its use are outside the scope of this
document.For a comparison of the overhead of IP-TFS with the RFC4303
prescribed TFC solution see .Additionally, IP-TFS provides for dealing with network congestion
. This is important for when the IP-TFS user is not in full
control of the domain through which the IP-TFS tunnel path flows.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
when, and only when, they appear in all capitals,
as shown here.This document assumes familiarity with IP security concepts described
in .As mentioned in IP-TFS utilizes an IPsec tunnel
(SA) as it's transport. To provide for full TFC, fixed-sized
encapsulating packets are sent at a constant rate on the tunnel.The primary input to the tunnel algorithm is the requested bandwidth
of the tunnel. Two values are then required to provide for this
bandwidth, the fixed size of the encapsulating packets, and rate at
which to send them.The fixed packet size may either be specified manually or can be
determined through the use of Path MTU discovery and .Given the encapsulating packet size and the requested tunnel
bandwidth, the corresponding packet send rate can be calculated. The
packet send rate is the requested bandwidth divided by the payload
size of the encapsulating packet.The egress of the IP-TFS tunnel MUST allow for and expect the ingress
(sending) side of the IP-TFS tunnel to vary the size and rate of
sent encapsulating packets, unless constrained by other policy.As previously mentioned, one issue with the TFC padding solution in
is the large amount of wasted bandwidth as only one IP
packet can be sent per encapsulating packet. In order to maximize
bandwidth IP-TFS breaks this one-to-one association.IP-TFS aggregates as well as fragments the inner IP traffic flow into
fixed-sized encapsulating IPsec tunnel packets. Padding is only added
to the the tunnel packets if there is no data available to be sent at
the time of tunnel packet transmission, or if fragmentation has been
disabled by the receiver.This is accomplished using a new Encapsulating Security Payload (ESP,
) type which is identified by the number IPTFS_PROTOCOL
().The IPTFS_PROTOCOL payload content defined in this document is
comprised of a 4 or 24 octet header followed by either a partial, a
full or multiple partial or full data blocks. The following diagram
illustrates this IPTFS_PROTOCOL payload within the ESP packet. See
for the exact formats of the IPTFS_PROTOCOL payload.The BlockOffset value is either zero or some offset into or past
the end of the DataBlocks data.If the BlockOffset value is zero it means that the DataBlocks
data begins with a new data block.Conversely, if the BlockOffset value is non-zero it points to the
start of the new data block, and the initial DataBlocks data
belongs to a previous data block that is still being re-assembled.The BlockOffset can point past the end of the DataBlocks data
which indicates that the next data block occurs in a subsequent
encapsulating packet.Having the BlockOffset always point at the next available data
block allows for recovering the next full inner packet in the
presence of outer encapsulating packet loss.An example IP-TFS packet flow can be found in .A data block is defined by a 4-bit type code followed by the data
block data. The type values have been carefully chosen to coincide
with the IPv4/IPv6 version field values so that no per-data block
type overhead is required to encapsulate an IP packet. Likewise, the
length of the data block is extracted from the encapsulated IPv4 or
IPv6 packet's length field.It's worth noting that since a data block type is identified by its
first octet there is never a need for an implicit pad at the end of
an encapsulating packet. Even when the start of a data block occurs
near the end of a encapsulating packet such that there is no room for
the length field of the encapsulated header to be included in the
current encapsulating packet, the fact that the length comes at a
known location and is guaranteed to be present is enough to fetch the
length field from the subsequent encapsulating packet payload. Only
when there is no data to encapsulated is end padding required, and
then an explicit Pad Data Block would be used to identify the
padding.In order for a receiver to be able to reassemble fragmented
inner-packets, the sender MUST send the inner-packet fragments
back-to-back in the logical IP-TFS packet stream (i.e., using
consecutive ESP sequence numbers). However, the sender is allowed to
insert "all-pad" IP-TFS packets (i.e., packets having payloads with a
BlockOffset of zero and a single pad DataBlock) in between the
IP-TFS packets carrying the inner-packet fragment payloads. This
possible interleaving of all-pad packets allows the sender to always
be able to send an IP-TFS tunnel packet, regardless of the
encapsulation computational requirements.When a receiver is reassembling an inner-packet, and it receives an
"all-pad" IP-TFS tunnel packet, it increments the expected sequence
number that the next inner-packet fragment is expected to arrive in.In order to support reporting of congestion control information
(described later) on a non-IP-TFS enabled SA, IP-TFS allows for the
sending of an IP-TFS payload with no data blocks (i.e., the ESP
payload length is equal to the IP-TFS header length). This special
payload is called an empty payload. provides some direction on when and how to map various values
from an inner IP header to the outer encapsulating header, namely the
Don't-Fragment (DF) bit ( and ), the Differentiated
Services (DS) field and the Explicit Congestion Notification
(ECN) field . Unlike , IP-TFS may and often will be
encapsulating more than one IP packet per ESP packet. To deal with
this, these mappings are restricted further. In particular
IP-TFS never maps the inner DF bit as it is unrelated to the IP-TFS
tunnel functionality; IP-TFS never IP fragments the inner packets and
the inner packets will not affect the fragmentation of the outer
encapsulation packets. Likewise, the ECN value need not be mapped as
any congestion related to the constant-send-rate IP-TFS tunnel is
unrelated (by design!) to the inner traffic flow. Finally, by default
the DS field SHOULD NOT be copied although an implementation MAY
choose to allow for configuration to override this behavior. An
implementation SHOULD also allow the DS value to be set by
configuration.It is not the intention of this specification to allow for mixed use
of an IP-TFS enabled SA. In other words, an SA that has IP-TFS
enabled is exclusively for IP-TFS use and MUST NOT have non-IP-TFS
payloads such as IP (IP protocol 4), TCP transport (IP protocol 6),
or ESP pad packets (protocol 59) intermixed with non-empty IP-TFS (IP
protocol TBD1) payloads. While it's possible to envision making the
algorithm work in the presence of sequence number skips in the IP-TFS
payload stream, the added complexity is not deemed worthwhile. Other
IPsec uses can configure and use their own SAs.Just as with normal IPsec/ESP tunnels, IP-TFS tunnels are
unidirectional. Bidirectional IP-TFS functionality is achieved by
setting up 2 IP-TFS tunnels, one in either direction.An IP-TFS tunnel can operate in 2 modes, a non-congestion controlled
mode and congestion controlled mode.In the non-congestion controlled mode IP-TFS sends fixed-sized
packets at a constant rate. The packet send rate is constant and is
not automatically adjusted regardless of any network congestion
(e.g., packet loss).For similar reasons as given in the non-congestion
controlled mode should only be used where the user has full
administrative control over the path the tunnel will take. This is
required so the user can guarantee the bandwidth and also be sure as
to not be negatively affecting network congestion . In this
case packet loss should be reported to the administrator (e.g.,
via syslog, YANG notification, SNMP traps, etc) so that any
failures due to a lack of bandwidth can be corrected.With the congestion controlled mode, IP-TFS adapts to network
congestion by lowering the packet send rate to accommodate the
congestion, as well as raising the rate when congestion subsides.
Since overhead is per packet, by allowing for maximal fixed-size
packets and varying the send rate transport overhead is minimized.The output of the congestion control algorithm will adjust the rate
at which the ingress sends packets. While this document does not
require a specific congestion control algorithm, best current
practice RECOMMENDS that the algorithm conform to . Congestion
control principles are documented in as well. An example of
an implementation of the algorithm which matches the
requirements of IP-TFS (i.e., designed for fixed-size packet and send
rate varied based on congestion) is documented in .The required inputs for the TCP friendly rate control algorithm
described in are the receiver's loss event rate and the
sender's estimated round-trip time (RTT). These values are provided by
IP-TFS using the congestion information header fields described in
. In particular these values are sufficient to
implement the algorithm described in .At a minimum, the congestion information must be sent, from the
receiver and from the sender, at least once per RTT. Prior to
establishing an RTT the information SHOULD be sent constantly from
the sender and the receiver so that an RTT estimate can be
established. The lack of receiving this information over multiple
consecutive RTT intervals should be considered a congestion event
that causes the sender to adjust it's sending rate lower. For
example, calls this the "no feedback timeout" and it is equal
to 4 RTT intervals. When a "no feedback timeout" has occurred
halves the sending rate.An implementation MAY choose to always include the congestion
information in it's IP-TFS payload header if sending on an IP-TFS
enabled SA. Since IP-TFS normally will operate with a large packet
size, the congestion information should represent a small portion of
the available tunnel bandwidth. An implementation choosing to always
send the data MAY also choose to only update the LossEventRate
and RTT header field values it sends every RTT though.When an implementation is choosing a congestion control algorithm (or
a selection of algorithms) one should remember that IP-TFS is not
providing for reliable delivery of IP traffic, and so per packet ACKs
are not required and are not provided.It's worth noting that the variable send-rate of a congestion
controlled IP-TFS tunnel, is not private; however, this send-rate is
being driven by network congestion, and as long as the encapsulated
(inner) traffic flow shape and timing are not directly affecting the
(outer) network congestion, the variations in the tunnel rate will
not weaken the provided inner traffic flow confidentiality.In additional to congestion control, implementations MAY choose to
define and implement circuit breakers as a recovery method
of last resort. Enabling circuit breakers is also a reason a user may
wish to enable congestion information reports even when using the
non-congestion controlled mode of operation. The definition of
circuit breakers are outside the scope of this document.In order to support the congestion control mode, the sender needs to
know the loss event rate and also be able to approximate the RTT
(). In order to obtain these values the receiver sends
congestion control information on it's SA back to the sender. Thus,
in order to support congestion control the receiver must have a
paired SA back to the sender (this is always the case when the tunnel
was created using IKEv2). If the SA back to the sender is a
non-IP-TFS enabled SA then an IPTFS_PROTOCOL empty payload (i.e.,
header only) is used to convey the information.In order to calculate a loss event rate compatible with , the
receiver needs to have a round-trip time estimate. Thus the sender
communicates this estimate in the RTT header field. On startup this
value will be zero as no RTT estimate is yet known.In order for the sender to estimate it's RTT value, the sender
places a timestamp value in the TVal header field. On first receipt
of this TVal, the receiver records the new TVal value along with
the time it arrived locally, subsequent receipt of the same TVal
MUST not update the recorded time. When the receiver sends it's CC
header it places this latest recorded value in the TEcho header
field, along with 2 delay values, Echo Delay and Transmit Delay.
The Echo Delay value is the time delta from the recorded arrival
time of TVal and the current clock in microseconds. The second
value, Transmit Delay, is the receiver's current transmission delay
on the tunnel (i.e., the average time between sending packets on it's
half of the IP-TFS tunnel). When the sender receives back it's TVal
in the TEcho header field it calculates 2 RTT estimates. The first
is the actual delay found by subtracting the TEcho value from it's
current clock and then subtracting Echo Delay as well. The second
RTT estimate is found by adding the received Transmit Delay header
value to the senders own transmission delay (i.e., the average time
between sending packets on it's half of the IP-TFS tunnel). The
larger of these 2 RTT estimates SHOULD be used as the RTT value.
The two estimates are required to handle different combinations of
faster or slow tunnel packet paths with fast or slow fixed tunnel
rates. Choosing the larger of the two values guarantees that the
RTT is never considered faster than the aggregate transmission
delay based on the IP-TFS tunnel rate (the second estimate), as well
as never being considered faster than the actual RTT along the tunnel
packet path (the first estimate).The receiver also calculates, and communicates in the LossEventRate
header field, the loss event rate for use by the sender. This is
slightly different from which periodically sends all the loss
interval data back to the sender so that it can do the calculation.
See for a suggested way to
calculate the loss event rate value. Initially this value will be
zero (indicating no loss) until enough data has been collected by the
receiver to update it.In additional to normal packet loss information IP-TFS supports use
of the ECN bits in the encapsulating IP header for
identifying congestion. If ECN use is enabled and a packet arrives at
the egress endpoint with the Congestion Experienced (CE) value set,
then the receiver considers that packet as being dropped, although it
does not drop it. The receiver MUST set the E bit in any
IPTFS_PROTOCOL payload header containing a LossEventRate value
derived from a CE value being considered.As noted in the ECN bits are not protected by IPsec and
thus may constitute a covert channel. For this reason ECN use SHOULD
NOT be enabled by default.IP-TFS is meant to be deployable with a minimal amount of
configuration. All IP-TFS specific configuration should be able to be
specified at the unidirectional tunnel ingress (sending) side. It
is intended that non-IKEv2 operation is supported, at least, with
local static configuration.Bandwidth is a local configuration option. For non-congestion
controlled mode the bandwidth SHOULD be configured. For
congestion controlled mode one can configure the bandwidth
or have no configuration and let congestion control discover the
maximum bandwidth available. No standardized configuration method is
required.The fixed packet size to be used for the tunnel encapsulation packets
can be configured manually or can be automatically determined using
Path MTU discovery (see and ). No standardized
configuration method is required.Congestion control is a local configuration option. No standardized
configuration method is required.When using IKEv2, a new "USE_IPTFS" Notification Message is used to
enable operation of IP-TFS on a child SA pair. The method used is
similar to how USE_TRANSPORT_MODE is negotiated, as described in
.To request IP-TFS operation on the Child SA pair, the initiator
includes the USE_IPTFS notification in an SA payload requesting a new
Child SA (either during the initial IKE_AUTH or during non-rekeying
CREATE_CHILD_SA exchanges). If the request is accepted then response
MUST also include a notification of type USE_IPTFS. If the responder
declines the request the child SA will be established without IP-TFS
enabled. If this is unacceptable to the initiator, the initiator MUST
delete the child SA.The USE_IPTFS notification MUST NOT be sent, and MUST be ignored,
during a CREATE_CHILD_SA rekeying exchange as it is not allowed to
change IP-TFS operation during rekeying.The USE_IPTFS notification contains a 1 octet payload of flags that
specify any requirements from the sender of the message. If any
requirement flags are not understood or cannot be supported by the
receiver then the receiver should not enable IP-TFS mode (either by
not responding with the USE_IPTFS notification, or in the case of the
initiator, by deleting the child SA if the now established non-IP-TFS
operation is unacceptable).The notification type and payload flag values are defined in .ESP Payload Type: 0x5An IP-TFS payload is identified by the ESP payload type IPTFS_PROTOCOL
which has the value 0x5. The first octet of this payload indicates the
format of the remaining payload data.An 8 bit value indicating the payload format.This specification defines 2 payload sub-types. These payload formats
are defined in the following sections.The non-congestion control IPTFS_PROTOCOL payload is comprised of a 4
octet header followed by a variable amount of DataBlocks data as
shown below.An octet indicating the payload format. For this
non-congestion control format, the value is 0.An octet set to 0 on generation, and ignored on
receipt.A 16 bit unsigned integer counting the number of
octets of DataBlocks data before the start of a
new data block. BlockOffset can count past the end
of the DataBlocks data in which case all the
DataBlocks data belongs to the previous data block
being re-assembled. If the BlockOffset extends
into subsequent packets it continues to only count
subsequent DataBlocks data (i.e., it does not
count subsequent packets non-DataBlocks octets).Variable number of octets that begins with the start
of a data block, or the continuation of a previous
data block, followed by zero or more additional data
blocks.The congestion control IPTFS_PROTOCOL payload is comprised of a 24
octet header followed by a variable amount of DataBlocks data as
shown below.An octet indicating the payload format. For this
congestion control format, the value is 1.A 7 bit field set to 0 on generation, and ignored on
receipt.A 1 bit value if set indicates that Congestion Experienced
(CE) ECN bits were received and used in deriving the
reported LossEventRate.The same value as the non-congestion controlled
payload format value.A 32 bit value specifying the inverse of the
current loss event rate as calculated by the
receiver. A value of zero indicates no loss.
Otherwise the loss event rate is
1/LossEventRate.A 22 bit value specifying the sender's current round-trip
time estimate in microseconds. The value MAY be zero prior
to the sender having calculated a round-trip time estimate.
The value SHOULD be set to zero on non-IP-TFS enabled SAs.
If the value is equal to or larger than 0x3FFFFF it MUST
be set to 0x3FFFFF.A 21 bit value specifying the delay in microseconds
incurred between the receiver first receiving the TVal
value which it is sending back in TEcho. If the value
is equal to or larger than 0x1FFFFF it MUST be set to
0x1FFFFF.A 21 bit value specifying the transmission delay in
microseconds. This is the fixed (or average) delay on the
receiver between it sending packets on the IPTFS tunnel.
If the value is equal to or larger than 0x1FFFFF it MUST
be set to 0x1FFFFF.An opaque 32 bit value that will be echoed back by the
receiver in later packets in the TEcho field, along with a
Delay value of how long that echo took.The opaque 32 bit value from a received packet's TVal
field. The received TVal is placed in TEcho along with
a Delay value indicating how long it has been since
receiving the TVal value.Variable number of octets that begins with the start
of a data block, or the continuation of a previous
data block, followed by zero or more additional data
blocks. For the special case of sending congestion
control information on an non-IP-TFS enabled SA this
value MUST be empty (i.e., be zero octets long).A 4 bit field where 0x0 identifies a pad data block, 0x4
indicates an IPv4 data block, and 0x6 indicates an IPv6
data block.These values are the actual values within the encapsulated IPv4
header. In other words, the start of this data block is the start of
the encapsulated IP packet.A 4 bit value of 0x4 indicating IPv4 (i.e., first nibble of
the IPv4 packet).The 16 bit unsigned integer "Total Length" field of
the IPv4 inner packet.These values are the actual values within the encapsulated IPv6
header. In other words, the start of this data block is the start of
the encapsulated IP packet.A 4 bit value of 0x6 indicating IPv6 (i.e., first nibble of
the IPv6 packet).The 16 bit unsigned integer "Payload Length" field
of the inner IPv6 inner packet.A 4 bit value of 0x0 indicating a padding data block.extends to end of the encapsulating packet.As discussed in a notification message
USE_IPTFS is used to negotiate IP-TFS operation in IKEv2.The USE_IPTFS Notification Message State Type is (TBD2).The notification payload contains 1 octet of requirement flags. There
are currently 2 requirement flags defined. This may be revised by
later specifications.6 bits - reserved, MUST be zero on send, unless defined by
later specifications.Congestion Control bit. If set, then the sender is requiring
that congestion control information MUST be returned to it
periodically as defined in .Don't Fragment bit, if set indicates the sender of the notify
message does not support receiving packet fragments (i.e., inner
packets MUST be sent using a single Data Block). This value only
applies to what the sender is capable of receiving; the sender MAY
still send packet fragments unless similarly restricted by the
receiver in it's USE_IPTFS notification.This document requests a protocol number IPTFS_PROTOCOL be allocated
by IANA from "Assigned Internet Protocol Numbers" registry for
identifying the IP-TFS payload.TBD1An IP-TFS payload.This documentThis document requests IANA create a registry called "IPTFS_PROTOCOL
Sub-Type Registry" under "IPTFS_PROTOCOL Parameters" IANA registries.
The registration policy for this registry is "Standards Action"
( and ).IPTFS_PROTOCOL Sub-Type RegistryIPTFS_PROTOCOL Payload Formats.This documentThis initial content for this registry is as follows:This document requests a status type USE_IPTFS be allocated
from the "IKEv2 Notify Message Types - Status Types" registry.TBD2USE_IPTFSThis documentThis document describes a mechanism to add Traffic Flow
Confidentiality to IP traffic. Use of this mechanism is expected to
increase the security of the traffic being transported. Other than
the additional security afforded by using this mechanism, IP-TFS
utilizes the security protocols and and so their
security considerations apply to IP-TFS as well.As noted previously in , for TFC to be
fully maintained the encapsulated traffic flow should not be
affecting network congestion in a predictable way, and if it would be
then non-congestion controlled mode use should be considered instead.Key words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.IP Encapsulating Security Payload (ESP)This document describes an updated version of the Encapsulating Security Payload (ESP) protocol, which is designed to provide a mix of security services in IPv4 and IPv6. ESP is used to provide confidentiality, data origin authentication, connectionless integrity, an anti-replay service (a form of partial sequence integrity), and limited traffic flow confidentiality. This document obsoletes RFC 2406 (November 1998). [STANDARDS-TRACK]Internet Key Exchange Protocol Version 2 (IKEv2)This document describes version 2 of the Internet Key Exchange (IKE) protocol. IKE is a component of IPsec used for performing mutual authentication and establishing and maintaining Security Associations (SAs). This document obsoletes RFC 5996, and includes all of the errata for it. It advances IKEv2 to be an Internet Standard.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Applied Cryptography: Protocols, Algorithms, and Source Code in CInternet ProtocolPath MTU discoveryThis memo describes a technique for dynamically discovering the maximum transmission unit (MTU) of an arbitrary internet path. It specifies a small change to the way routers generate one type of ICMP message. For a path that passes through a router that has not been so changed, this technique might not discover the correct Path MTU, but it will always choose a Path MTU as accurate as, and in many cases more accurate than, the Path MTU that would be chosen by current practice. [STANDARDS-TRACK]Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 HeadersThis document defines the IP header field, called the DS (for differentiated services) field. [STANDARDS-TRACK]Congestion Control PrinciplesThe goal of this document is to explain the need for congestion control in the Internet, and to discuss what constitutes correct congestion control. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.The Addition of Explicit Congestion Notification (ECN) to IPThis memo specifies the incorporation of ECN (Explicit Congestion Notification) to TCP and IP, including ECN's use of two bits in the IP header. [STANDARDS-TRACK]Security Architecture for the Internet ProtocolThis document describes an updated version of the "Security Architecture for IP", which is designed to provide security services for traffic at the IP layer. This document obsoletes RFC 2401 (November 1998). [STANDARDS-TRACK]Profile for Datagram Congestion Control Protocol (DCCP) Congestion Control ID 3: TCP-Friendly Rate Control (TFRC)This document contains the profile for Congestion Control Identifier 3, TCP-Friendly Rate Control (TFRC), in the Datagram Congestion Control Protocol (DCCP). CCID 3 should be used by senders that want a TCP-friendly sending rate, possibly with Explicit Congestion Notification (ECN), while minimizing abrupt rate changes. [STANDARDS-TRACK]TCP Friendly Rate Control (TFRC): Protocol SpecificationThis document specifies TCP Friendly Rate Control (TFRC). TFRC is a congestion control mechanism for unicast flows operating in a best-effort Internet environment. It is reasonably fair when competing for bandwidth with TCP flows, but has a much lower variation of throughput over time compared with TCP, making it more suitable for applications such as streaming media where a relatively smooth sending rate is of importance.This document obsoletes RFC 3448 and updates RFC 4342. [STANDARDS-TRACK]Early IANA Allocation of Standards Track Code PointsThis memo describes the process for early allocation of code points by IANA from registries for which "Specification Required", "RFC Required", "IETF Review", or "Standards Action" policies apply. This process can be used to alleviate the problem where code point allocation is needed to facilitate desired or required implementation and deployment experience prior to publication of an RFC, which would normally trigger code point allocation. The procedures in this document are intended to apply only to IETF Stream documents.Encapsulating MPLS in UDPThis document specifies an IP-based encapsulation for MPLS, called MPLS-in-UDP for situations where UDP (User Datagram Protocol) encapsulation is preferred to direct use of MPLS, e.g., to enable UDP-based ECMP (Equal-Cost Multipath) or link aggregation. The MPLS- in-UDP encapsulation technology must only be deployed within a single network (with a single network operator) or networks of an adjacent set of cooperating network operators where traffic is managed to avoid congestion, rather than over the Internet where congestion control is required. Usage restrictions apply to MPLS-in-UDP usage for traffic that is not congestion controlled and to UDP zero checksum usage with IPv6.Network Transport Circuit BreakersThis document explains what is meant by the term "network transport Circuit Breaker". It describes the need for Circuit Breakers (CBs) for network tunnels and applications when using non-congestion- controlled traffic and explains where CBs are, and are not, needed. It also defines requirements for building a CB and the expected outcomes of using a CB within the Internet.Guidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.Internet Protocol, Version 6 (IPv6) SpecificationThis document specifies version 6 of the Internet Protocol (IPv6). It obsoletes RFC 2460.Path MTU Discovery for IP version 6This document describes Path MTU Discovery (PMTUD) for IP version 6. It is largely derived from RFC 1191, which describes Path MTU Discovery for IP version 4. It obsoletes RFC 1981.The Wire Image of a Network ProtocolThis document defines the wire image, an abstraction of the information available to an on-path non-participant in a networking protocol. This abstraction is intended to shed light on the implications on increased encryption has for network functions that use the wire image.Below an example inner IP packet flow within the encapsulating tunnel
packet stream is shown. Notice how encapsulated IP packets can start
and end anywhere, and more than one or less than 1 may occur in a
single encapsulating packet.The encapsulated IP packet flow (lengths include IP header and
payload) is as follows: an 800 octet packet, an 800 octet packet, a 60
octet packet, a 240 octet packet, a 4000 octet packet.The BlockOffset values in the 4 IP-TFS payload headers for this
packet flow would thus be: 0, 100, 2900, 1400 respectively. The first
encapsulating packet ESP1 has a zero BlockOffset which points at the
IP data block immediately following the IP-TFS header. The following
packet ESP2s BlockOffset points inward 100 octets to the start of the
60 octet data block. The third encapsulating packet ESP3 contains the
middle portion of the 4000 octet data block so the offset points past
its end and into the forth encapsulating packet. The fourth packet
ESP4s offset is 1400 pointing at the padding which follows the
completion of the continued 4000 octet packet.The current best practice indicates that congestion control SHOULD be
done in a TCP friendly way. A TCP friendly congestion control algorithm
is described in . For this IP-TFS use case (as with ) the
(fixed) packet size is used as the segment size for the algorithm. The
main formula in the algorithm for the send rate is then as follows:Where X is the send rate in packets per second, R is the
round trip time estimate and p is the loss event rate (the inverse
of which is provided by the receiver).In addition the algorithm in also uses an X_recv value (the
receiver's receive rate). For IP-TFS one MAY set this value according to
the sender's current tunnel send-rate (X).The IP-TFS receiver, having the RTT estimate from the sender can use the
same method as described in and to collect the loss
intervals and calculate the loss event rate value using the weighted
average as indicated. The receiver communicates the inverse of this
value back to the sender in the IPTFS_PROTOCOL payload header field
LossEventRate.The IP-TFS sender now has both the R and p values and can calculate
the correct sending rate. If following the sender SHOULD also
use the slow start mechanism described therein when the IP-TFS SA is
first established.The overhead of IP-TFS is 40 bytes per outer packet. Therefore the
octet overhead per inner packet is 40 divided by the number of outer
packets required (fractional allowed). The overhead as a percentage of
inner packet size is a constant based on the Outer MTU size.The overhead per inner packet for constant-send-rate padded ESP
(i.e., traditional IPsec TFC) is 36 octets plus any padding, unless
fragmentation is required.When fragmentation of the inner packet is required to fit in the
outer IPsec packet, overhead is the number of outer packets required
to carry the fragmented inner packet times both the inner IP overhead
(20) and the outer packet overhead (36) minus the initial inner IP
overhead plus any required tail padding in the last encapsulation
packet. The required tail padding is the number of required packets
times the difference of the Outer Payload Size and the IP Overhead
minus the Inner Payload Size. So:The following tables collect the overhead values for some common L3
MTU sizes in order to compare them. The first table is the number of
octets of overhead for a given L3 MTU sized packet. The second table
is the percentage of overhead in the same MTU sized packet.Another way to compare the two solutions is to look at the amount of
available bandwidth each solution provides. The following sections
consider and compare the percentage of available bandwidth. For the
sake of providing a well understood baseline normal (unencrypted)
Ethernet as well as normal ESP values are included.In order to calculate the available bandwidth the per packet overhead
is calculated first. The total overhead of Ethernet is 14+4 octets of
header and CRC plus and additional 20 octets of framing (preamble,
start, and inter-packet gap) for a total of 38 octets. Additionally
the minimum payload is 46 octets.A sometimes unexpected result of using IP-TFS (or any packet
aggregating tunnel) is that, for small to medium sized packets, the
available bandwidth is actually greater than native Ethernet. This is
due to the reduction in Ethernet framing overhead. This increased
bandwidth is paid for with an increase in latency. This latency is
the time to send the unrelated octets in the outer tunnel frame. The
following table illustrates the latency for some common values on a
10G Ethernet link. The table also includes latency introduced by
padding if using ESP with padding.Notice that the latency values are very similar between the two
solutions; however, whereas IP-TFS provides for constant high
bandwidth, in some cases even exceeding native Ethernet, ESP with
padding often greatly reduces available bandwidth.We would like to thank Don Fedyk for help in reviewing and editing
this work.The following people made significant contributions to this document.