Network Working Group M. Beckman
Internet Draft: 03 U.S. Department of Defense
Category: Standards Track 22 February 2007
IPv6 Dynamic Flow Label Switching (FLS)
draft-martinbeckman-ietf-ipv6-fls-ipv6flowswitching-03.txt
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Copyright (C) The IETF Trust (2007).
Abstract
This document seeks to establish a standard for the utilization of the
Class of Service Field and the us of the Flow Label Field within the IPv6
Header and establish a methodology of switching packets through routers
using the first 32-bits of the IPv6 header using Flow Label Switching on
packets rather than full routing of packets. Within the first 32-bits
of an IPv6 header exists the requisite information to allow for the
immediate switching on an ingress packet of a router, allowing for
Label Switching of a native IPv6 packet. This allows the establishment
of VPN circuits in a dynamic manner across transit networks. The
establishment of Flows based upon the 20-bit Flow Label value can be
done dynamically with minimal effort and configuration of the end-point
routers of the flow. The flows can be managed or open, encrypted or in the
clear, and will allow for greater scalability, security, and agility in
the management and operation of networks.
Comments are solicited and should be addressed to martin.beckman@disa.mil
Beckman Standards Track [Page 1]
Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The Flow Label Switching Traffic Class . . . . . . . . . . . . . . 3
4. Flow Label Switching Setup and Management . . . . . . . . . . . . . 4
5. Managed Flow Label Switching . . . . . . . . . . . . . . . . . . . 5
6. Encrypted Flow Label Switching . . . . . . . . . . . . . . . . . . 6
7. Flow Sets and Queuing . . . . . . . . . . . . . . . . . . . . . . . 9
8. Contextual Uses of Flow Label Switching . . . . . . . . . . . . . . 9
9. Intellectual Property Statement . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . 10
12. Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction and Abstract
To traverse the Internet or any large enterprise network, each router hop
represents a decision point about the life cycle of each datagram. A major
latency inducing function is the look-up of the destination of the packet
in the routing table of each router along the way. This is for simplistic
routing. If there are additional considerations, such as queuing or
filtering, the process can become more laborious. Additionally, two or
more networks requiring secure communications require the establishment of
a VPN tunnel to assure security of the traffic as it traverses the
backbone or in most cases,a carriers internetworking autonomous system. In
all cases, the entire IPv6 header of 320 bits must be read, cached, and
processed at each router along the path etween the networks. What is
proposed is a methodology of determining the destination port for a packet
at is enters a router within the first 32-bits of information. This can be
done using a hierarchical methodology of applying values to the Traffic
Class Field (8-bits) and switching the packet based upon he value of the
Flow Label Field (20-bits) based upon a flow label switching table within
the router. The only requirement is that all routers along the paths
available can read the Traffic Class Field and are capable of Flow Label
Switching.
The Flow Switch Path is dynamically established by the two end-point
routers with simple recognition of the flow by the intervening Next-Hop-
Routers along the paths between the two End Point Routers. The flows are
capable of being controlled either manually or through a Flow Label
Server within an autonomous system. This is essential for the secure
functioning of a network or conflicting Flow Labels will result. Finally,
the Flow establishment and operation is encrypt-able, allowing for secure
establishment and operation between the two end point routers of the flow.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Succinctly put, packets can be switched based upon Flow Label Value
allowing for a myriad of possibilities in both topologies and secure
network operations across carriers across the globe. The end result is a
limiting of the need for VPN servers, IPv6 tunnels, and greater mobility
of entire networks within an enterprise if proper planning and
considerations are understood. Since the packet remains "IPv6 native" the
ability to monitor and secure traffic becomes less problematic compared to
label switching" within the MPLS context. Instead of converting and non-
native IPv6 packet in MPLS form for read and analysis, the packet is
handled as any other packet on the network. This is critical when networks
use IP/IPv6 packet encryption since an MPLS packet is neither IP or IPv6
and cannot be handled by the encryption device with removing the MPLS shim
and thereby wrecking the overall end-to-end secure transmission process.
2. Definitions and Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [7].
Flow Initiating Router (FIR) The FIR is the router that initiates a flow
label switch path. The FIR sets the Traffic Class Field and Flow Label
Values to the required value to set the flow up across the routing fabric
between the two end points.
Flow Destination Router (FDR) The FDR is the router the FIR seeks to
establish a flow with. The FDR resets the Traffic Class Field and Flow
Label Values to the required value to send the packet to its final
destination based upon the path determined by the local routing table.
Next-Hop-Router (NHR) The NHR established and maintains the Flow Switch
Path using a Flow Switch Table that is maintained based upon instructions
from the FIR and its own local routing table.
Switched Flow Path (SFP) is the switched path taken by packet across a
Routed fabric based upon the value of the Flow Label and, if used, flow
set.
Flow Set (FS) a group of flows through a router identified by the FS value
in the Traffic Class.
Flow Path Server (FPS) is a physical or virtual host on the network the
FIR, FDR, and NHRs use to validate Flow Path setup requests.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
3. The Flow Label Switching Traffic Class.
The first requirement is to establish a flow path across a routed fabric
based upon a traffic class value within the defined parameters of RFC
2474. RFC 2474 currently defines three pools for traffic class use within
IPv6:
Pool Codepoint space Assignment Policy
---- --------------- -----------------
1 xxxxx0 Standards Action
2 xxxx11 EXP/LU
3 xxxx01 EXP/LU (*)
The codepoint space uses the first six bits of the 8 bits in the traffic
class field. Flow Label Switching uses the "top half" of the Traffic Class
field by setting the first bit to "1". Pool "128" would use codepoint
space of 1abcxxyy, where a,b, and c have values as list below. When "c" is
set to "0" and DF codepoint space is in use within a routed domain, "xx"
are direct mappings of pools 1, 2, and 3 into the traffic class field. The
values for "yy" are reserved.
The second requirement is to identify a packet as being flow switched
versus routed. To accomplish this, the Traffic Class Field is used.
In any event the packet is either routed of flow switched. Therefore,
the differentiation is set in the first bit of the Traffic Class Field,
which is set to 1 for flow switched. This leaves the lower half values of
the Traffic class (0-127) available of use in routing. The remaining
values of the Traffic class Field of a Flow Switched packet are as
follows:
| version | Traffic Class | Flow Label |
| 1 2 3 4 | 1 2 3 4 5 6 7 8 | 20 bits |
| 0 1 1 0 | 1 a b c d e f g | 1 - 1,048,574 |
Value a 0 = Open / 1 = Managed
Value b 0 = Clear / 1 = Encrypted
Value c 0 = Data Traffic / 1 = Flow Management Message
Values d through f are dependant upon the value of c.
Note: When "c" is set to "0" and RFC 2474 is in use, pools 1, 2, or 3
are manipulated per RFC 2474 and RFC 3168; therefore, the FIR and
FDR map d through g directly into the Traffic Class field.
Pool 128 has a codepoint value of" 1dddxx with an assignment policy of
Flow Label Switching where "d" is the defined value per this document and
"x" is the value defined in RFC 2474. Pool 128 has a range of 128 to 255.
When the fourth bit (c) is set to "0" the packet is user traffic moving
across the flow. The balance of 4 bits is used for priority,
differentiating between inter-AS or intra AS Flows, or a combination of
both when RFC 2474 Differentiated Service (DS) and RFC 3168, Explicit
Congestion Notification (ECN) is not in use. This allows for 16
priorities, sixteen different set of flows, or a combination of differing
flow sets with internal priority queues.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
When it is a combination of both, priority is set first, and the flow set
is set second. As an example, two flow sets (blue and red) are set in
field g with blue or red being a value of 0 and the other a value of 1.
Each flow set then has 3 bits for setting priority using d f. As a
cautionary note; by not following RFC 2474 and RFC 3168, Explicit Congestion
Notification cannot be used.
When c = 1, the packet is a Flow Management Packet between the two end
point routers (the FIR and FDR) as well as for the intervening NHRs along
the flow path. The follow are the Values of d though g in this
circumstance and are covered in the mechanics of setting of a Flow Switch
Path:
| d e f g | Decimal | Purpose
| 0 0 0 0 | 0 |Set up an Asymmetric Flow
| 0 0 0 1 | 1 |Set up a Symmetric Flow
| 0 0 1 0 | 2 |NHR Acknowledgment
| 0 0 1 1 | 3 |NHR Failed
| 0 1 0 0 | 4 |Restart Flow
| 0 1 0 1 | 5 |Keep Alive from FIR
| 0 1 1 0 | 6 |Keep Alive from FDR
| 0 1 1 1 | 7 |Flow Tear Down
| 1 n n 0 | 8-14 |FPS Management
| 1 1 1 1 | 15 |Reserved
4. Flow Label Switching Setup and Management
Across a routed fabric, a switched flow is initiated by a Flow Initiation
Router (FIR). To accomplish this, the router has a virtual interface
established with a routable 128-bit Unicast address. The Flow Destination
Router has the same setup with a different routable 128-bit Unicast
address. The initiating packet from the FIR to the FDR is as follows:
|version| Traffic Class | Flow Label |
|1 2 3 4| 1 2 3 4 5 6 7 8 | 20 bits |
|0 1 1 0| 1 0 0 1 0 0 0 0 | 0-FE |
____________________________________________
|Payload Length | Next Hdr 59| Hop Limit |
____________________________________________
| |
| FIR 128-bit Address |
| |
____________________________________________
| |
| FDR 128-bit Address |
| |
____________________________________________
| Next Header 59 and Padding |
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
This establishes a simple, asymmetric Flow Path. The FIR send the packet
via the destination port of the FDR based upon the route listed in the
routing table.
The FIR then sets the flow label value with the end-points into a flow
switch table and marks the label as the router being an end-point for the
flow. The Next Hop Router (NHR) receives the packet and established an
entry in the flow switch table based upon the routing table as port to the
FIR and FDR associated with the flow label. Since this flow in asymmetric,
the ports used by the flow path could be dissimilar is the best paths per
the routing table have an asymmetric pattern. This is possible for Flows
over ASNs where BGP parameters may make ingress and egress to another AS
asymmetric. For Symmetric flows, bit 5 is set to one, and the NHR simply
duplicates the Flow Switch Table Entry reversing the ingress/egress ports
for the flow label association. Once the flow switch table is updated by
the NHR, the packet is sent to the next NHR on the routed path, each
updating its own Flow Switch Table. The NHR then sends an acknowledgement
to the sending router with a TC field of:
1 n n 1 0 0 1 0, where n is the value of the TC filed received.
This is of importance later when flows are setup as managed, with or
without encryption. The receiving this acknowledgement then marks the Flow
Switch Table entries as active. This process through the NHRs continues
until the packet is received by the FDR. Since the destination address is
local to the router, the FDR then sets the flow label value with the end-
points into a flow switch table and marks the label as the router being an
end-point for the flow. The FDR then sends a keep-alive to the FIR with
a TC value of 1 n n 1 0 1 1 0 via the flow path established.
The FIR will send a keep-alive with a TC value of 1 n n 1 0 1 0 1. Both
the FIR and FDR will send their respective keep-alive packets over the
flow path on a varying interval of 1-180 seconds. If the end point routers
do not receive a keep-alive from their respective end-point, the FIR
and/or FDR will send a restart message using a TC Value of:
1 n n 1 0 1 0 0.
This initiates the Flow over the NHR path. The purpose of the restart
message is to force the NHRs on the path to revalidate the Flow Switch
table entry for that particular flow. During the startup phase of the
flow. If there is a duplicate flow label entry in an NHR along the path
(Example: The Network Administrator attempts to use the same flow label
values for two different sets of end points, that NHR sends back a NHR
Fail message with a TC value of 1 n n 1 0 0 1 1. Any Reviving NHR then
drops that entry from the flow switch table and forwards the messages back
to the FIR. The FIR then logs to console and drops the flow setup. The
Flow Switch Table entries for Next Hop Routers (NHRs) remains valid for 1
to 30 minutes if there are no packets matching the entry. The purpose for
this control is to purge unused flow paths from the routed path
automatically; however, care should be taken to ensure the FIR/FDR Keep-
Alive messages transpire within the purge time set.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
5. Managed Flow Label Switching
In the proceeding section, the flows are openly established from one FIR
to and FDR with automatic processing by the intervening NHRs along the
routed path. While convenient and possibly applicable within a large
enterprise network, the management of possibly over 1 million flows will
become problematic. Further, while Flow Label Switching is generally for
routers, flows could conceivably be established between hosts on the
network for a variety of purposes such as server-to-server updating and
archiving, true peer-to-peer networking where latency of service is
problematic; however, the openness of open flow label switching allows
for greater risks to the routed infrastructure. To mitigate these risks
and allow for more centralized management, the second bit of the TC filed
can be set to one making the establishment of Flow Switch Paths centrally
controlled.
As a methodology, Managed Flow Switching is simple. The second bit of the
TC field is set to 1. Caching the packet, the receiving router then and
requests a validation of the Flow Path from a flow path server (FPS) on
the network. Multiple Flow Path Servers (FPS) are required for redundancy.
The recommended methodology would to imbed the server as an internal
service on a set of routers within the infrastructure with a common 128-
bit Anycast address for the server.
The transaction for setup should be simplistic and allow for secure means
of authentication between the routers and the FPS devices on the network.
The conceptual transaction methodology is as follows:
- A Flow Path Server is established on the network with a predetermined
Anycast Address available to only the routers or specified devices on
the network.
- Each router in the fabric has the Anycast address loaded in the
configuration to request a Flow Path Lookup. Additionally, each router
should be configurable to globally deny non-managed Flow Path Switching
request, yet have the option of permitting individual
- A Flow Path is loaded into the server with the Flow Label, Flow Set,
Priority, FIR Unicast Address, and the FDR Unicast Address.
- The Flow Label with Flow Set, Priority, and FDR Address are setup in
the FIR.
- The FIR requests validation of the Flow Path from the FPS.
- Once the FPS validates the Flow requested by the FIR and responds with
an acknowledgement, the NHR sends the set packet to the next NHR on
the Flow Path per the routing table.
- Caching the packet, the first NHR then and requests a validation of the
Flow Path from a flow path server (FPS) on the network. When the Flow is
validated, the request is forwarded to the next NHR on the path per the
local route table. Each NHR responds with an acknowledgement to the
requesting router as in the unmanaged flow operation.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
- The process repeats through the chain of NHRs until the request is
received by the FDR. Caching the packet, the FDR then and requests a
validation of the Flow Path from a flow path server (FPS) on the
network.
Once acknowledged, the FDR has acknowledgement, it sends a Keep-Alive
to the FIR as in the unmanaged flow.
Once the Flow Switching Path is established, the FPS is no longer used.
The validity on the Flow Switch Path continues to be maintained via keep-
alive packets between the endpoint routers and timers on the NHRs along
the path.
Inter-FPS updating for multiple FPS on a routed fabric is essential when
using Anycasting. Each FPS will belong to a hierarchy of servers, with one
being designated as the root server in a fashion similar to DNS; however,
the exchange need to take place via TCP in a point-to-point fashion. If a
flow is configured into a secondary server, the root server is notified.
In the event of a root server failure, the next server will assume the
role as root server. The recommended approach is to prioritize based upon
lowest MAC address or unicast end-station address or the servers.
Since updates are not immediate, A Flow Path Validation request will query
the closest FPS per Anycasting methodologies. If the Flow is not found,
the FPS queries the root server for an update. If not found the validation
fails, yet if the root FPS has the entry, is sends a validation to the
secondary server. The secondary server then updates its Flow Path
Database.
The root FPS will send an initial full database update to the secondary
FPS and will only send adds and drop on a periodic basis after that. If a
new secondary FPS is placed into the service, the root server must be
manually configured with the address on the secondary servers unicast
address. The root FPS will then send the full database to the secondary
FPS. A secondary FPS will not request and update. This precludes a rouge
FPS from hijacking the FPS database.
The FPS database will identify the following:
- Current Root FPS by Unicast Address
- All Secondary FPS by Unicast Address
- All Flow Path Entries including FIR by Unicast Address, FDR by
Unicast Address, Flow Label Value, Flow Set Value (If used),
Flow Priority (If Used), Encryption TC bit setting, Flow Symmetry
Value, Time Last Keep-Alive received from FIR, keep alive interval.
The root FPS sends a Keep-Alive Query to the FIR and FDR for each flow.
The FIR and FDR each respond to their respective Anycast FPS. If an FPS
has not received an Acknowledgement from the End-Points within three
attempts, the FPS updates is local database and sends a Flow Failure
message to the root FPS. The root server takes three actions: Updates the
local database by suspending the Flow Path Information, Sends an FPS
Database Update to each secondary FPS, Sends a Flow Halt Message to the
End-points, The FIR in turn issues a Flow Tear Down Packet to the NHRs to
clear the entry from the FIR, FDR, and NHR local Flow Switch Table. The
ollowing is a summary of the second half of the TC field binary settings
sed with the 11n1 set first half of the TC.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Table Summary of the second half of the TC field binary settings
used with the 11n1 set first half of the TC.
| d e f g | Decimal | Purpose
| 1 0 0 0 | 8 |End Point Keep-Alive Query to FIR/FDR
| 1 0 0 1 | 9 |End Point Keep-Alive Acknowledgement from FIR/FDR
| 1 0 1 0 | 10 |Flow Halt, Issue Flow Teardown Message
| 1 0 1 1 | 11 |FPS Full Database Update (from root FPS to secondary FPS)
| 1 1 0 0 | 12 |FPS Full Database Ack (from secondary FPS to root FPS)
| 1 1 0 1 | 13 |FPS Database Update (from root FPS to secondary FPS)
| 1 1 1 0 | 14 |FPS Database Ack (from secondary FPS to root FPS)
| 1 1 1 1 | 15 |Flow Failure from secondary FPS to root FPS
6. Encrypted Flow Label Switching
The envisioned use of Flow Label Switching is to allow communities of
interest connected to a common infrastructure to connect internally to
each other without the overhead associated with tunneling or VPN
arrangements; however, the Flows need to be secure from monitoring in some
cases, as the packets traverse a common backbone or carrier level
Autonomous System. This section deals with purpose and use of the third
(3rd) bit of the TC Field for encrypting the Flows between Endpoints via
either locally agreeable encryption between the endpoint routers (or hosts
of the Flows are between Servers, or via a PPKI infrastructure setup.
To encrypt a Flow Path, the FIR sets the third bit of the TC field to a
value of one (1). There are two possible methodologies: In the Clear Setup
and Management with Encrypted Traffic or Complete Encryption. There are
also two levels of Encryption: First 32-bit in the clear and the Entire
IPv6 Header in the Clear. In all cases, this is not to be confused with
IPv6 security and authentication headers! That is a separate function
performed by the end station hosts traversing the network and is
functionally performed after the actual IPv6 header is read. In this
context, only the first 32-bits of the header are being read to determine
a switching decision.
6.a. Encryption Methodologies
In the Clear Setup and Management with Traffic Encryption, while less
scure, has logically less overhead for the intervening NHRs along the Flow
Switch Path.
In this case, all Flow Setup and management is (fourth bit of the TC filed
is set to one) done as previously described, except that the third bit of
the TC field is set to one. Once the Flow Switch path is established
between the two endpoints, the FIR and FDR exchange keys or perform
another authentication and encryption algorithm. The FIR and FDR then
encrypt all Traffic traversing the Flow Switch Path at either a high level
or a low level. Simplistically, the transmitter encrypts and the receiver
decrypts.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Complete Encryption is far more extensive in that all participating
routers and, in the case of Managed Flow Label Switching, the Flow Path
Servers (FPS)Encrypt all traffic, after the first 32-bits of the header.
In this case the unicast addresses of the end-points of the Flow Switch
Path are hidden from view by traffic monitoring. Problematic to this is
having all of the routers (as well as possibly hosts) and participating
FPS devices encrypting and decrypting all Flow Label Management Packets.
This will increase processor overhead as well as add to the complexity
of what is meant to be a simplistic, yet dynamic switching protocol;
however, the actual traffic traversing the flow switch path only
encrypted and decrypted by the end-point routers of the Flow Switch
Path.
6.b. Encryption Levels
In this context, the level of encryption corresponds depth within the
packet that the encryption takes place and the type of encryption (IE:
Strong or Weak). The Encryption Algorithm determines the strength, the
level determines how much of the header and packet is encrypted. The
level is determined as part of the exchange between the end-point
routers on the Flow Switch Path.
The difference between High level and Low level is that High level
encryption scrambles all information after the Hop-Limit Field in the
IPv6 packet, making the destination and source addresses as well as the
type and content of the datagram unreadable as it passes through the NHR
fabric. Low level Encryption scrambles all data after the source and
destination address. This allows the destination and source addresses as
well as the next header field to be monitored as the packet traverses
the NHRs on the Flow Switch path.
7. Flow Sets and Queuing
Once a Flow Switching path is established, the end-points of the flow will
have a TC value of: 1 m n 0 a b c d, where m = managed/open, n =
encrypted/clear, and the fourth bit is set to 1. The remaining four bits
(0-F) can be parsed for two uses: Flow Set Identification or Flow
Priority. This feature is to allow equal flow values to be shared on a
set of NHRs by differentiating them through a Flow Setvalue similar to
concept of an ATM Virtual Path Identifier differentiating equal value for
Virtual Circuit Identifiers (VCIs). Alternatively, the 16-bits can be used
to prioritize which flow has priority on the routers switching based upon
Flow Value. Conceivably, a Next Hop Router in a large Transit Network with
multiple flows may receive Flow Switched packets on several ports over a
brief interval of time. This allows the switching function of the router
to queue the traffic based upon the value set in the 16 bits as the
priority level. In this case, each flow has 16 priority levels of traffic,
allowing a differentiation of latency sensitive traffic versus generic
best effort traffic. Finally, the combination of the two methodologies.
Flow Sets can be determine in the first one to three bits leaving the
remainder for Priority queuing of traffic. Alternatively, the first 1 to 3
bits can determine priority allowing for equal priority flow sets to be
established.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
8. Contextual Uses and Security Considerations of Flow Label Switching
There exist two functional advantages for Flow Label Switching versus
continuing with MPLS.
First, it affords an alternative to MPLS by establishing VPN circuits between
to remote routers. This alternative, unlike MPLS, is dynamic and sets up
flows across a routed fabric without having to reconfigure the intervening
routers. Second, it allows for faster determination of a packets destiny as
it ingresses into a router without resorting to mutating the IPv6 packet by
adding a shim. Rather than read the entire 320-bit packet header and
executing a closest match route lookup, only the first 32 bits are read and
the packet is switched to an egress port, sending the packet on its way with
90% less effort in what to read to determine what to do.
Both these facets allow for some interesting capabilities for aggregation of
geographically separate locations behind a single DMZ structure. Since each
end-point sends and receives packets based upon Flow Label Value, forming an
adjacency is formed between the two virtual Flow Label Interfaces, allowing
the flow to act similar to a tunnel across a Wide Area Network. Router A sees
Router B directly through their respective Flow Interfaces, allowing either A
or B to act as the overall gateway for the other network.
This can extremely effective for large organizations such as the Government
or Corporations who have internal organizations that each operate on
differing security policies. In this context, each internal organization can
be wrapped into a single security domain with a simplifying restructuring
of the DMZ. This mitigates the need for VPN servers in numerous cases, and
due to the dynamic setup nature of both Clear and Managed Flow Switching
Paths, the mobility of entire networks can be readily achieved.
Unlike MPLS, Flow Label Switching operates within the IPv6 protocols defined
header specification. More succinctly put, the IPv6 packet may have the
values of the Traffic Class and Flow Label fields manipulated, but it stills
remains a native IPv6 packet, unlike MPLS which as a 32-bit shim. This is
critical for government use when the data flow must traverse the newer
generation of High Assurance IP Encryptor (HAIPE) devices used within US
Department of Defense and elsewhere in the US Government. As stated in the
name of the device; it is an IP Encryptor and not an MPLS Encryptor! MPLS
poses difficult problems for this family of encryption devices currently
being deployed as a replacement for link layer encryption devices.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Returning to the concept of non-encapsulated tunneling, FLS paths are
established using the routing tables of the routers along the path. This
allows for a far more rapid fielding of flows across a routed infrastructure
when compared to the implementation of MPLS. Since the flow is established
between two virtual interfaces (similar to tunnel interfaces) the virtual
interfaces establish link local address connectivity at layer 3 (via the
FEC0::/16) routing between these two virtual interfaces is as easily achieved
as it is using standard tunneling. As a practical matter, the implementation
of this protocol within a routing OS should be as a subset of tunneling
protocols, where the tunnel interface number may be equal to the flow label
value. The ramifications of this enhancement go directly to the
simplification of network operations for service providers and the reduction
of costs for connectivity between geographically diverse locations within an
enterprise. The following are two uses for this capacity:
Military/Government: Within the Defense Community, the major services (Army,
Nay, Air Force, and Marine Corps) as well as the Joint Unified Commands and
the various Defense Agencies are widely dispersed throughout the globe. Each
of these various entities maintain unclassified interconnectivity via the DoD
ISP NIPRNet. Since each one of these entities maintains their own security
policies, each entity insists that their external traffic all originate from
behind a consolidated DMZ structure. FLS simplifies this critical issue by
providing secured flows between the sites to a specific DMZ. Additionally,
each flow may be encrypted to where only the first 64 bits of the header are
in the clear. This permits the destination and source addresses within the
flow as well as the data to be hidden while the packet is switched through a
common routed infrastructure to somewhere else within the enterprises
security domain. Finally, the military moves and deploys routinely. FLS
permits for additional flows to be established on the fly for those deploying
units permitting simplified and continuous connectivity to all domains
required. This has considerable tactical, operational, and strategic value!
Commercial/Corporate: As an example, a large manufacturing corporation
has numerous production facilities throughout the globe and providing secure
and monitored access becomes both costly and problematic. Each site need only
achieve IPv6 network access with FLS provided as a service. Each site then
can be folded logically and virtually behind a single DMZ and have secure
capability between sites. The sites no longer need numerous circuits
enmeshing them with each other for a substantial reduction in recurring
operational costs.
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
9. References
[RFC 2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC 3697] J. Rajahalme, Nokia; A. Conta, Transwitch; B. Carpenter, IBM
S. Deering, Cisco; IPv6 Flow Label Specification, RFC 3697, March 2004.
[RFC 3595] B. Wijnen, Lucent Technologies; Textual Conventions for IPv6 Flow
Label, RFC 3595, September 2003.
[RFC 3168] K. Ramakrishnan, TeraOptic Networks; S. Floyd, ACIRI; D. Black, EMC
The Addition of Explicit Congestion Notification (ECN) to IP, RFC 3168
September 2001.
[RFC 2774 K. Nichols, Cisco Systems; S. Blake, Torrent Networking Technologies;
F. Baker, Cisco Systems; D. Black, EMC Corporation, Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers,
December 1998.
[RFC 3168] K. Ramakrishnan, TeraOptic Networks; S. Floyd, ACIRI; D. Black, EMC;
The Addition of Explicit Congestion Notification (ECN) to IP,
September 2001.
10. Acknowledgments
My thanks to Brian Carpenter (brc@zurich.ibm.com) for redirecting my efforts to
ensure that inclusion of DS Field definition per RFC 2474 was properly addressed
and patiently reviewing the details.
11. Intellectual Property Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions contained in
BCP 78, and except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
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Internet Draft: 03 IPv6 Dynamic Flow Label Switching (FLS) February 2007
Individual Property Rights
By submitting this Internet-Draft, each author represents that any applicable
Patent or other IPR claims of which he or she is aware have been or will be
disclosed, and any of which he or she becomes aware will be disclosed, in
accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
12. Author's Address
Martin Beckman
Defense Information Systems Agency
5275 Leesburg Pike, 7 Skyline Place
Falls Church, VA 22041
United States of America
Phone: 703-861-6865 // 703-882-0225
EMail: martin.beckman@disa.mil
Beckman Standards Track [Page 12]