draft-ietf-ipsecme-iptfs-09.txt   draft-ietf-ipsecme-iptfs-10.txt 
Network Working Group C. Hopps Network Working Group C. Hopps
Internet-Draft LabN Consulting, L.L.C. Internet-Draft LabN Consulting, L.L.C.
Intended status: Standards Track July 5, 2021 Intended status: Standards Track September 3, 2021
Expires: January 6, 2022 Expires: March 7, 2022
IP-TFS: Aggregation and Fragmentation Mode for ESP and its Use for IP IP-TFS: Aggregation and Fragmentation Mode for ESP and its Use for IP
Traffic Flow Security Traffic Flow Security
draft-ietf-ipsecme-iptfs-09 draft-ietf-ipsecme-iptfs-10
Abstract Abstract
This document describes a mechanism for aggregation and fragmentation This document describes a mechanism for aggregation and fragmentation
of IP packets when they are being encapsulated in ESP payload. This of IP packets when they are being encapsulated in ESP payload. This
new payload type can be used for various purposes such as decreasing new payload type can be used for various purposes such as decreasing
encapsulation overhead for small IP packets; however, the focus in encapsulation overhead for small IP packets; however, the focus in
this document is to enhance IPsec traffic flow security (IP-TFS) by this document is to enhance IPsec traffic flow security (IP-TFS) by
adding Traffic Flow Confidentiality (TFC) to encrypted IP adding Traffic Flow Confidentiality (TFC) to encrypted IP
encapsulated traffic. TFC is provided by obscuring the size and encapsulated traffic. TFC is provided by obscuring the size and
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 6, 2022. This Internet-Draft will expire on March 7, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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number based sliding window can be used to correct re-ordering of the number based sliding window can be used to correct re-ordering of the
outer packet stream. Receiving a larger (newer) sequence number outer packet stream. Receiving a larger (newer) sequence number
packet advances the window, and received older ESP packets whose packet advances the window, and received older ESP packets whose
sequence numbers the window has passed by are dropped. A good choice sequence numbers the window has passed by are dropped. A good choice
for the size of this window depends on the amount of re-ordering the for the size of this window depends on the amount of re-ordering the
user may normally experience. user may normally experience.
As the amount of reordering that may be present is hard to predict, As the amount of reordering that may be present is hard to predict,
the window size SHOULD be configurable by the user. Implementations the window size SHOULD be configurable by the user. Implementations
MAY also dynamically adjust the reordering window based on actual MAY also dynamically adjust the reordering window based on actual
reordering seen in arriving packets. Finally, note that as IP-TFS is reordering seen in arriving packets.
sending a continuous stream of packets there is no requirement for
timers (although there's no prohibition either) as newly arrived Please note when IP-TFS sends a continuous stream of packets, there
packets will cause the window to advance and older packets will then is no requirement for an explicit drop timer; however, using a drop
be processed as they leave the window. Implementations that are timer is RECOMMENDED. If an implementation does not use a drop timer
concerned about memory use when packets are delayed (e.g., when an SA and only considers an outer packet lost when the reorder window moves
deletion is delayed), or non-IP-TFS uses of AGGFRAG mode, can of by it, the inner traffic can be delayed by up to the reorder window
course use timers to drop packets as well. size times the per packet send rate. This amount of delay could be
significant for slower send rates or when larger reorder window sizes
are in use.
While ESP guarantees an increasing sequence number with subsequently While ESP guarantees an increasing sequence number with subsequently
sent packets, it does not actually require the sequence numbers to be sent packets, it does not actually require the sequence numbers to be
generated with no gaps (e.g., sending only even numbered sequence generated with no gaps (e.g., sending only even numbered sequence
numbers would be allowed as long as they are always increasing). numbers would be allowed as long as they are always increasing).
Gaps in the sequence numbers will not work for this document so the Gaps in the sequence numbers will not work for this document so the
sequence number stream MUST increase monotonically by 1 for each sequence number stream MUST increase monotonically by 1 for each
subsequent packet. subsequent packet.
When using the AGGFRAG_PAYLOAD in conjunction with replay detection, When using the AGGFRAG_PAYLOAD in conjunction with replay detection,
the window size for both MAY be reduced to the smaller of the two the window size for both MAY be reduced to the smaller of the two
window sizes. This is because packets outside of the smaller window window sizes. This is because packets outside of the smaller window
but inside the larger would still be dropped by the mechanism with but inside the larger would still be dropped by the mechanism with
the smaller window size. However, there is also no requirement to the smaller window size. However, there is also no requirement to
make these values the same. Indeed, in some cases, such as slow make these values the same. Indeed, in some cases, such as slow
tunnels where a very small or zero reorder window size is tunnels where a very small or zero reorder window size is
appropriate, the user may want a large replay detection window to log appropriate, the user may still want a large replay detection window
replayed packets. Additionally, large replay windows can be to log replayed packets. Additionally, large replay windows can be
implemented with very little overhead compared to large reorder implemented with very little overhead compared to large reorder
windows. windows.
Finally, as sequence numbers are reset when switching SAs (e.g., when Finally, as sequence numbers are reset when switching SAs (e.g., when
re-keying a child SA), senders MUST NOT send initial fragments of an re-keying a child SA), senders MUST NOT send initial fragments of an
inner packet using one SA and subsequent fragments in a different SA. inner packet using one SA and subsequent fragments in a different SA.
2.2.3.1. Optional Extra Padding 2.2.3.1. Optional Extra Padding
When the tunnel bandwidth is not being fully utilized, a sender MAY When the tunnel bandwidth is not being fully utilized, a sender MAY
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