icnrg J. Auge, Ed.
Internet-Draft G. Carofiglio
Intended status: Informational L. Muscariello
Expires: 11 December 2020 M. Papalini
Cisco Systems Inc.
June 2020
MAP-Me : Managing Anchorless Mobility in Content Centric Networking
draft-irtf-icnrg-mapme-05
Abstract
Consumer mobility is supported in ICN by design, in virtue of its
connectionless pull-based communication model; producer mobility
though is not natively supported. This document describes MAP-Me, an
anchor-less solution to manage micro-mobility of content producers in
the CCN (Content Centric Networking) and NDN (Named Data Networking)
architectures, with support for latency-sensitive applications. MAP-
Me consists in the combination of two data plane protocols, triggered
by producer movements, and leveraging ICN named-based data plane.
The main protocol consists in a lightweight FIB update process,
complemented by a mechanism of local notification and scoped
discovery suitable for low latency applications and fast mobility.
Status of This Memo
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This Internet-Draft will expire on 3 December 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. MAP-Me overview . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Anchor-less mobility management . . . . . . . . . . . . . 4
2.2. Design principles . . . . . . . . . . . . . . . . . . . . 4
2.3. MAP-Me protocols . . . . . . . . . . . . . . . . . . . . 5
3. Update protocol . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Update propagation . . . . . . . . . . . . . . . . . . . 6
3.3. Concurrent updates . . . . . . . . . . . . . . . . . . . 10
4. Notification protocol and scoped discovery . . . . . . . . . 12
4.1. Interest Notification . . . . . . . . . . . . . . . . . . 12
4.2. Scoped discovery . . . . . . . . . . . . . . . . . . . . 13
4.3. Full approach . . . . . . . . . . . . . . . . . . . . . . 13
5. Implementation . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. MAP-Me messages . . . . . . . . . . . . . . . . . . . . . 13
5.2. Data structures and temporary state . . . . . . . . . . . 14
5.3. Algorithm description . . . . . . . . . . . . . . . . . . 14
5.3.1. Producer attachment and face creation . . . . . . . . 15
5.3.2. IU/IN transmission at producer . . . . . . . . . . . 15
5.3.3. IU/IN transmission at network routers . . . . . . . . 15
5.3.4. Reliable transmission . . . . . . . . . . . . . . . . 16
5.3.5. Consumer request forwarding in case of producer
discovery . . . . . . . . . . . . . . . . . . . . . . 17
5.3.6. Producer departure and face destruction . . . . . . . 18
6. Security considerations . . . . . . . . . . . . . . . . . . . 18
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.1. Normative References . . . . . . . . . . . . . . . . . . 18
9.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
With the phenomenal spread of portable user devices, mobility has
become a basic requirement for almost any communication network as
well as a compelling feature to integrate in the next generation
networks (5G). The need for a mobility-management paradigm to apply
within IP networks has striven a lot of efforts in research and
standardization bodies (IETF, 3GPP among others), all resulting in a
complex access-dependent set of mechanisms implemented via a
dedicated control infrastructure. The complexity and lack of
flexibility of such approaches (e.g. Mobile IP) calls for a
radically new solution dismantling traditional assumptions like
tunneling and anchoring of all mobile communications into the network
core. This is particularly important with the increase in rates and
mobile nodes (IoT), a vast amount of which never moves.
The Information Centric Network (ICN) paradigm brings native support
for mobility, security, and storage within the network architecture,
hence emerging as a promising 5G technology candidate. Specifically
on mobility management, ICN has the potential to relieve limitations
of the existing approaches by leveraging its primary feature, the
redefinition of packet forwarding based on "names" rather than
"network addresses". Removing the dependence on location identifiers
is a first step in the direction of removing the need for any
anchoring of communications into fixed network nodes, which may
considerably simplify and improve mobility management. Within the
ICN paradigm, several architectures have been proposed, as reported
in [SURVEY12] and [SURVEY14].
As a direct result of CCN/NDN design principles, consumer mobility is
natively supported: a change in physical location for the consumer
does not translate into a change in the data plane like for IP. The
retransmission of requests for data not yet received by the consumer
takes place without involving any signaling to the network. Producer
mobility and realtime group communications present more challenges,
depending on the frequency of movements, latency requirements, and
content lifetime. The topology does not reflect the naming
structure, and the mobility management process has to preserve key
functionalities such as multipath, caching, etc. In all cases,
beyond providing connectivity guarantees, additional transport-level
mechanisms might be required to protect the flow performance (see
[WLDR] for instance).
MAP-Me aims at tackling such problems by exploiting key CCN/NDN
characteristics. Previous attempts have been made in CCN/NDN (and
ICN in general) literature to go beyond the traditional IP
approaches, by using the existing CCN/NDN request/data packet
structures to trace producer movements and to dynamically build a
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reverse-forwarding path (see [SURVEY16b] for a survey). They still
rely on a stable home address to inform about producer movements or
on buffering of incoming requests at the producer's previous point of
attachment (PoA), which prevents support for latency-sensitive
streaming applications. The approach presented in this document
makes a particular focus on this class of applications (e.g. live
streaming or videoconferencing) as they have the most stringent
performance requirements: negligible per-packet loss-rate and delays.
In addition, they typically originate from a single producer and
don't allow for the use of caching.
MAP-Me defines a name-based mechanism operating in the forwarding
plane and completely removing any anchoring, while aiming at latency
minimization. Its performance and guarantees of correctness,
stability and bounded stretch are analyzed in [MAPME].
2. MAP-Me overview
2.1. Anchor-less mobility management
Many efforts have been made to define mobility-management models for
IP networks in the last two decades, resulting in a variety of
complex, often not implemented, proposals. A survey of these
approaches is proposed in [RFC6301]. Likewise, within ICN, different
approaches to mobility management have been presented [SURVEY13].
Specifically for the CCN/NDN solutions, several surveys of mobility-
management approaches can be found [SURVEY16a] [SURVEY16b].
We follow here the classification presented in [MAPME] which
highlights their reliance on indirection/rendez-vous points. In
particular, a new class of anchor-less approaches is introduced, in
which the present proposal fits. Such solutions are less common and
have been introduced in ICN to remove the need for anchor points in
the data plane, but also in the control plane in the form of
resolution or mapping services. These solutions completely remove
the use of locators and extend the ICN forwarding mechanisms with
mobility support.
2.2. Design principles
* *Micro-Mobility* : MAP-Me addresses micro (e.g. intra Autonomous
Systems) producer mobility. Addressing macro-mobility is a non-
goal of the proposal. We are focusing here on complementary
mechanisms able to provide a fast and lightweight handover,
preserving the performance of flows in progress.
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- *Control Plane Agnostic* : MAP-Me _is control-plane agnostic as
it does not rely on routing updates or path computation_, which
would be too slow and too costly, but rather works at a faster
timescale propagating forwarding updates on a single path. It
also leverages real-time notifications left as breadcrumbs by
the producer to enable live tracking of its content prefixes
and avoid buffering at intermediate nodes. MAP-Me shares the
use of data plane mechanisms for ensuring connectivity with
[DATAPLANE] which was originally proposed for link failures.
This enables the support of high-speed mobility and real-time
group applications. In addition, MAP-Me mobility updates are
issued at prefix granularity, rather than content or chunk/
packet granularity, to minimize signaling overhead and
temporary state kept by in-network nodes, and scale to large
and dynamic mobile networks.
* *Access-agnostic* : MAP-Me handles mobility at Layer 3 and is
designed to be access-agnostic, to cope with highly heterogeneous
wireless access and multi-homed/mobile users.
* *Decentralized and localized* : MAP-Me is designed to be fully
_decentralized_, to enhance robustness w.r.t. centralized mobility
management proposals subject to single point-of-passage problem.
MAP-Me updates are _localized_ and affect a minimum number of
routers at the edge of the network to restore connectivity. This
effectively realizes traffic off-load close to the end-users.
* *Transparent* : MAP-Me does not involve any name nor modifications
to basic request/reply operations to be compatible with standard
CCN/NDN design and to avoid issues caused by name modifications
like triangular routing, caching degradation, or security
vulnerabilities. It does not require consumers or producers to be
aware of the mobility of the remote endpoint, nor to perform any
handover prediction.
* *Robust* : to network conditions (e.g. routing failure, wireless
or congestion losses, and delays), by implementing hop-by-hop
retransmissions of mobility updates.
2.3. MAP-Me protocols
As a data plane protocol, MAP-Me handles producer mobility events by
means of dynamic FIB updates with the objective of minimizing
unreachability of the producer. It relies on the existence of a
routing protocol responsible for creating/updating the FIB of all
routers, possibly with multipath routes, and for managing network
failures (eg. [NLSR]).
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MAP-Me is composed of:
* an Update protocol, detailed in Section 3, which is the central
component of the proposal;
* a Notification/Discovery protocol, presented in Section 4, which
is coupled with the Update protocol to enhance reactivity for
realtime/latency-sensitive application, and reduce overhead during
fast mobility events.
3. Update protocol
3.1. Rationale
The rationale behind MAP-Me is that the producer announces its
movements to the network for all served prefixes, by sending a
special Interest packet - named Interest Update (IU) - to "itself"
after it reattaches to the network. Such a message looks like a
regular Interest packet named with the prefix advertised by the
producer. As such, it is forwarded according to the information
stored in the FIBs of traversed routers towards all previous
locations of the producer known by router FIBs. A special flag
carried in the header of the IU enables all routers on the path to
identify the Interest as a mobility update and to process it
accordingly to update their FIBs (a detailed description of the IU
processing is provided in Section 5.3).
The key aspect of the proposal is that it removes the need for a
stable home address by directly leveraging name-based forwarding
information created by CCN/NDN routing protocols, and eventually
further updated due to mobility. FIB updates are triggered by the
reception of mobility updates in a fully decentralized way and allow
an on-the-fly modification to point to the latest known location of
the producer.
3.2. Update propagation
The role of the update process is to quickly restore global
reachability of mobile prefixes with low signaling overhead, while
introducing a bounded maximum path stretch (the ratio between the
selected and the shortest path in terms of hops).
Let us illustrate its behavior through an example where a single
producer serving prefix /p moves from position P0 to P1 and so on.
Figure 1 (a) shows the initial tree formed by the forwarding paths to
the name prefix /p, and on which any IU initiated by the producer
will propagate.
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+---+ +---+
| 0 | P0 | 0 | P0
+---+ +---+
^ ^ ^ ^
/ \ / \
+---+ +---+ +---+ +---+
| 0 | | 0 | | 0 | | 0 |
+---+ +---+ +---+ +---+
^ ^ ^ ^
/ \ / \
+---+ +---+ +---+ +---+
| 0 | | 0 | | 0 | | 0 |
+---+ +---+ A +---+ +---+
^ ^ IU1 / ^ ^
/ \ / / \
+---+ +---+ .... .+---+. +---+
| 0 | | 0 | . P1 | 1 | . | 0 |
+---+ +---+ . +---+ . +---+
^ ^ . ^ ^ .
/ \ . / \ .
+---+ +---+ . +---+ +---+ .
| 0 | | 0 | . | 0 | | 0 | .
+---+ +---+ . +---+ +---+ .
..................
(a) (b)
Figure 1: IU propagation example
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.................
+---+ ... +---+ ..
| 0 | P0 . | 1 | P0 .
+---+ . A +---+ .
^ ^ . IU(1) / / ^ .
/ \ . / V \ .
+---+ +---+ . +---+ +---+ .
| 0 | | 0 | . | 1 | | 0 | .
+---+ +---+ . A +---+ +---+ .
^ ^ . IU(1) / / ^ .
/ \ . / V \ .
........+---+. +---+ . +---+ +---+ .
. | 1 | . | 0 | . | 1 | | 0 | .
. FIB +---+ . +---+ . A +---+ +---+ .
. updated / ^ . . IU(1) / / ^ .
. V \ .... . / V \ .
. +---+ +---+ . . +---+ +---+ .
. P1 | 1 | | 0 | . . P1 | 1 | | 0 | .
. +---+ +---+ . . +---+ +---+ .
. ^ ^ . . ^ ^ .
. / \ . . / \ .
. +---+ +---+ . . +---+ +---+ .
. | 0 | | 0 | . . | 0 | | 0 | .
. +---+ +---+ . . +---+ +---+ .
.................. ..................
(a) (b)
Figure 2: IU propagation example
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+---+
| 1 | P1
+---+
^ A ^
/ | \
+---+ +---+ +---+
| 0 | | 0 | | 1 |
+---+ +---+ +---+
^ ^
/ \
+---+ +---+
| 0 | | 1 |
+---+ +---+
^ ^
/ \
+---+ +---+
P0 | 1 | | 0 |
+---+ +---+
^
/
+---+
| 0 |
+---+
Figure 3: IU propagation example
Network FIBs are assumed to be populated with routes towards P0 by a
name-based routing protocol. After the relocation of the producer
from P0 to P1, once the layer-2 attachment is completed, the producer
issues an IU carrying the prefix /p and this is forwarded by the
network toward P0 (in general, toward one of its previous locations
according to the FIB state of traversed routers).
Figure 1 (b) illustrates the propagation of the IU. As the IU
progresses, FIBs at intermediate hops are updated with the ingress
face of the IU (Figure 2 (a) and (b)). IU propagation stops when the
IU reaches P0 and there is no next hop to forward it to. The result
is that the original tree rooted in P0 becomes re-rooted in P1
(Figure 3). Looking at the different connected regions (represented
with dotted lines), we see that IU propagation and consequent FIB
updates have the effect of extending the newly connected subtree : at
every step, an additional router and its predecessors are included in
the connected subtree.
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3.3. Concurrent updates
Frequent mobility of the producer may lead to the propagation of
concurrent updates. To prevent inconsistencies in FIBs, MAP-Me
maintains a sequence number at the producer end that is incremented
at each handover and associated to all sent IU packets. Network
routers also keep track of such sequence number in their FIBs to
validate the relative freshness of received updates. The
modification of FIB entries is only triggered when the received IU
carries a higher sequence number than the locally stored one, while
the reception of a less recent update triggers the transmission of a
more up-to-date IU backwards in order to fix the not-yet-updated
path.
An example reconciliation of concurrent updates is illustrated in
Figure 4 (a), when the producer has moved successively to P1 and then
to P2 before the first update could complete.
+---+ +---+
| 0 | P0 | 2 | P0
+---+ A +---+
^ ^ IU(2) / / ^
/ \ / V \
+---+ +---+ +---+ +---+
| 0 | | 0 | <!> | 2 | | 0 |
+---+ A +---+ A +---+ A +---+
^ ^ \ IU(1) / ^ \ \
/ \ \ IU(2) / / V \ IU(2)
+---+ +---+ +---+ +---+
| 0 | | 2 | P2 | 1 | | 2 |
A +---+ +---+ A +---+ +---+
IU(1) / ^ ^ IU1 / / ^
/ / \ / V \
+---+ +---+ +---+ +---+
P1 | 1 | | 0 | P1 | 1 | | 0 |
+---+ +---+ +---+ +---+
^ ^ ^ ^
/ \ / \
+---+ +---+ +---+ +---+
| 0 | | 0 | | 0 | | 0 |
+---+ +---+ +---+ +---+
(a) (b)
Figure 4
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+---+ +---+
| 2 | P0 | 2 | P2
+---+ +---+
/ ^ ^
V \ |
+---+ +---+ +---+
<!> | 2 | | 2 | | 2 |
IU(2) / +---+ +---+ +---+
/ ^ \ ^ ^
V / V / \
+---+ +---+ +---+ +---+
| 2 | | 2 | P2 P0 | 2 | | 2 |
IU(2) / +---+ +---+ +---+ +---+
/ / ^ ^ ^ ^
V V \ / P1 / \
+---+ +---+ +---+ +---+ +---+
P1 | 1 | | 0 | | 0 | | 2 | | 0 |
+---+ +---+ +---+ +---+ +---+
^ ^ ^ ^
/ \ / \
+---+ +---+ +---+ +---+
| 0 | | 0 | | 0 | | 0 |
+---+ +---+ +---+ +---+
(a) (b)
Figure 5
Both updates propagate concurrently until the one with sequence
number 1 (IU(1)) crosses a router that has been updated with fresher
information. In the example shown in Figure 4 (b), the junction
router has already received an IU with higher sequence number
(IU(2)). In this case, the router stops the propagation of IU(1) and
sends back along its path a new IU with an updated sequence number
(Figure 5 (a)). The update proceeds until the whole network has
ultimately converged towards P2 (Figure 5 (b)).
MAP-Me protocol reacts at a faster timescale than routing - allowing
more frequent and numerous mobility events - and over a localized
portion of the network edge between current and previous producer
locations. This allows to minimize disconnectivity time and reduce
link load, which are the main factors affecting user flow
performance, as shown in [MAPME] evaluations.
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4. Notification protocol and scoped discovery
IU propagation in the data plane is designed to accelerate forwarding
state re-convergence w.r.t. routing or resolution-based approaches
operating at control plane, and w.r.t. anchor-based approaches
requiring traffic tunneling through an anchor node. Still, network
latency makes IU completion not instantaneous and before an update
completes, it may happen that a portion of the traffic is forwarded
to the previous PoA and dropped because of the absence of a valid
output face leading to the producer.
Previous work in the Anchor-Less category has suggested the buffering
of Interests at previous producer location to prevent those losses.
However, such a solution is not suitable for applications with
stringent latency requirements (e.g. real-time) and may be
incompatible with IU completion times. Moreover, the negative
effects on latency performance might be further exacerbated by IU
losses and consequent retransmissions in case of wireless medium. To
alleviate such issues, we introduce two enhancements to the
previously described behavior, namely (i) an "Interest Notification"
mechanism for frequent, yet lightweight, signaling of producer
movements to the network and (ii) a scoped "Producer Discovery"
mechanism for consumer requests to proactively search for the
producer's recently visited locations.
4.1. Interest Notification
An Interest Notification (IN) is a breadcrumb left by producers at
every encountered PoA. It looks like a normal Interest packet
carrying a special identification flag and a sequence number, like
IUs. Both IU and IN share the same sequence number (producers
indistinctly increase it for every sent message) and follow the same
FIB lookup and update processes. However, unlike IU packets, the
trace left by INs at the first hop router does not propagate further.
It is rather used by the discovery process to route consumer requests
to the producer even before an update process is completed.
It is worth observing that updates and notifications serve the same
purpose of informing the network of a producer movement. The IU
process restores connectivity and as such has higher latency/
signaling cost than the IN process, due to message propagation. The
IN process provides information to track producer movements before
update completion when coupled with a scoped discovery. The
combination of both IU and IN allows to control the trade-off between
protocol reactivity and stability of forwarding re-convergence.
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4.2. Scoped discovery
The extension of MAP-Me with notifications relies on a local
discovery phase: when a consumer Interest reaches a PoA with no valid
output face in the corresponding entry, the Interest is tagged with a
"discovery" flag and labeled with the latest sequence number stored
in FIB (to avoid loops). From that point on, it is broadcasted with
hop limit equal to one to all neighbors and discarded unless it finds
a breadcrumb left by the producer with a higher sequence number. The
notifications can either allow to forward consumer Interests directly
to the producer or give rise to a repeated broadcast in case of no
valid output face. The latter is the case of a breadcrumb left by
the producer with no associated forwarding information because the
producer has already left that PoA as well. A detailed description
of the process is reported in Section 5.3.
The notification/discovery mechanism proves important to preserve the
performance of flows in progress, especially when latency-sensitive.
4.3. Full approach
The full MAP-Me approach consists in the combination of Updates and
Notifications through a heuristic allowing the producer or its PoA to
select which type of packet to send. One such heuristic consist in
sending a IN immediately after an attachment and a IU at most every
Tu seconds, which allows to reduce signaling overhead during periods
of high-mobility. The Tu parameter allows to tune the timescale at
which Updates occur, and leads to a trade-off between signaling and
discovery overhead [MAPME]. The definition of more advanced
heuristics is out of scope for the present draft.
5. Implementation
In this section we describe the changes to a regular CCN/NDN
architecture required to implement MAP-ME and detail the above-
described algorithms. This requires to specify a special Interest
message, additional temporary information associated to the FIB entry
and additional operations to update such entry.
5.1. MAP-Me messages
MAP-Me signaling messages are carried within user plane as special
Interest messages corresponding to "update" and "notification", and
their corresponding acknowledgements.
Two new optional fields are introduced in a CCN/NDN Interest header:
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* an "Interest Type" (T) used to specify one of the four types of
messages: Interest Update (IU), Interest Notification (IN), and as
well as their associated acknowledgment (Ack) messages (IU_Ack and
IN_Ack). Those flags are recognized by the forwarding pipeline to
trigger special treatment;
* a "sequence number" to handle concurrent updates and prevent
forwarding loops during signaling, and to control discovery
Interests' propagation;
5.2. Data structures and temporary state
FIB entries are augmented with information required for mobility
management, that we denote as Transient FIB buffer, or simply TFIB,
and sketch in Figure 6:
* a "sequence number" which is incremented upon reception of IU/IN
messages. It can be assumed this counter is set to 0 by the
routing protocol.
* a list of so-called "previous next hop(s)" (further denoted as
PrevHops), similar to the list of NextHops in the original FIB,
which temporarily stores information about faces that were
previously next hops, and should still be memorized to allow for
retransmissions and thus ensure the consistency of MAP-Me
operations. They typically correspond to nodes for which an IU
has been sent, but no acknowledgement (ACK) has yet been received
(upon which they are cleared). In case of notifications, no ACK
is expected, and those entries serve as a memory of the former
tree structure that will be restored upon producer departure. We
flag those entries with a boolean marker indicating if they
correspond to an IU (and thus should be monitored for
retransmissions) or an IN (in which case they just serve as memory
for further use).
IU (IN) input face(s) IU (IN) output face
+-----------+-------------------+.......+..........................+
| /prefix | { next hop(s) } | seq | { previous next hop(s) } |
+-----------+-------------------+.......+..........................+
\_____________ _______________/ \_______________ _______________/
V V
original FIB TFIB section
Figure 6: MAP-Me FIB/TFIB description
5.3. Algorithm description
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5.3.1. Producer attachment and face creation
MAP-Me operations are triggered by a change of adjacencies in the
network, reflected in the forwarder by the creation or removal of a
face. This can be for instance the layer 2 detachment and attachment
following a mobility/handover event, but also any other mechanism
such as point-to-point IP link or UDP tunnel for instance, as allowed
by the forwarder implementation.
One realization of this architecture is to delegate face management
to a third party agent, keeping the ICN forwarder state synchronized
with the underlying topology, and having MAP-Me only react to changes
in the face table.
5.3.2. IU/IN transmission at producer
The creation of a new face on the producer triggers the increase of
MAP-Me sequence number and the transmission for every locally served
prefix, of an IU or IN carrying the updated sequence number.
5.3.3. IU/IN transmission at network routers
At the reception of IU/IN packets, each router performs a name-based
Longest Prefix Match lookup in FIB to compare sequence number from
IU/IN and from FIB. According to that comparison:
* if the IU/IN packet carries a higher sequence number, the existing
next hops associated to the lower sequence number in FIB are used
to forward further the IU (INs are not propagated) and temporarily
copied into TFIB to avoid loss of such information before
completion of the IU/IN acknowledgement process. The ingress face
of the IU/IN is then added to FIB to route consumer requests to
the latest known location of the producer.
* If the IU/IN packet carries the same sequence number as in the
FIB, the originating face of the IU/IN is added to the existing
ones in FIB without additional packet processing or propagation.
This may occur in presence of multiple forwarding paths.
* If the IU/IN packet carries a lower sequence number than the one
in the FIB, FIB entry is not updated as it already stores 'fresher
information'. To advertise the latest update through the path
followed by the IU/IN packet, this one is re-sent through the
originating face after having updated its sequence number with the
value stored in FIB.
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The operations in the forwarding pipeline for IU/IN processing are
reported in Figure 7, where we make use of the following primitives:
- Send(Interest, Face) is used to send the specified Interest on the
specified Face. - ProcessTFIB() sends an IU for all flagged entries
in the TFIB, using the latest sequence number stored in the FIB
entry, and schedule the entry to be checked for retransmissions.
| Alg. 1:ForwardSpecialInterest(SpecialInterest SI,IngressFace F)
|
| CheckValidity()
| // Acknowledge reception
| s <- e.seq
| e.seq <- SI.seq
| Send(IU_Ack(e.seq), F)
flag <- (SI.type == IU)
| // Retrieve the FIB entry associated to the prefix
| e <- FIB.LongestPrefixMatch(SI.name)
| if SI.seq >= e.seq then
| . //Process special interest
| . e.TFIB = e.TFIB \ { F }
| . if SI.seq > s then
| . . e.TFIB = e.TFIB U { (f, flag) | f in (e.NextHops \ F) }
. . ProcessTFIB()
| . . e.NextHops = {}
| . e.NextHops = e.NextHops U { F }
| else
| . // Send updated IU backwards
| . SI.seq = e.seq
| . e.TFIB = e.TFIB U { (F, flag) }
| . ProcessTFIB()
Figure 7
5.3.4. Reliable transmission
MAP-Me ensure the reliable delivery of signaling messages thanks to a
retransmission timer which reissue Interest Updates (eventually
carrying updated sequence number as found in the FIB), if no
corresponding ACK has been received in a predefined interval, and
whose sequence number has to match the one stored in the FIB.
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A slotted implementation of such scheme is possible by using a single
timer, and keeping a list of FIB entries that require to be checked
for pending retransmissions in the next slot. Upon timer expiration,
if all required ACKs have been received, the TFIB will be empty and
the entry does not have to be tracked anymore. Otherwise, necessary
retransmissions are performed and the entry will be checked again in
the next slot. When no entry has to be monitored, the process can
sleep until the next mobility event.
5.3.5. Consumer request forwarding in case of producer discovery
The forwarding of regular Interests is mostly unaffected in MAP-Me,
except in the case of discovery Interests that we detail in Figure 8.
The function SendToNeighbors(I) is responsible for broadcasting the
Interest I to all neighboring PoAs.
| Alg. 2: InterestForward(Interest I, Origin face F)
|
| // Regular PIT and CS lookup
| e <- FIB.LongestPrefixMatch(I.name)
| if e = 0 then
| . return
| if I.seq = 0 then
| . // Regular interest
| . if hasValidFace(e.NextHops) or DiscoveryDisabled then
| . . ForwardingStrategy.process(I, e)
| . else
| . . // Enter discovery mode
| . . I.seq <- e.seq
| . . SendToNeighbors(I)
| else
| . // Discovery interest: forward if producer is connnected
| . if hasProducerFace(e.NextHops) then
| . . ForwardingStrategy.process(I, e)
| . // Otherwise iterate iif higher seq and breadcrumb
| . else if e.seq >= I.seq and \
| EXISTS f | (f -> NULL) in e.TFIB then
| . . I.seq <- e.seq
| . . SendToNeighbors(I)
Figure 8
When an Interest arrives to a PoA which has no valid next hop for it
(because the producer left and the face got destroyed), it enters a
discovery phase where the Interest is flagged as a Discovery Interest
and with the local sequence number, then broadcasted to neighboring
PoAs.
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Upon reception of a Discovery Interest, the PoA forwards it directly
to the producer if still attached, otherwise it repeats the one-hop
brodcast discovery to neighboring PoAs if it stores a recent
notification of the producer presence, i.e. an entry in TFIB having
higher sequence number than the one in the Discovery Interest.
Otherwise, the Discovery Interest is discarded.
It is worth observing that the discovery process is initiated only in
the case of no valid next hop, and not every time a notification is
found in a router. This is important to guarantee that the
notification/discovery process does not affect IU propagation and
completion.
5.3.6. Producer departure and face destruction
Upon producer departures from a PoA, the corresponding face is
destroyed. If this leads to the removal of the last next hop, then
faces in TFIB corresponding to IN are restored as next hops in the
FIB so as to preserve the original forwarding tree and thus global
connectivity.
6. Security considerations
All mobility management protocols share the same critical need for
securing their control messages which have a direct impact on the
forwarding of users' traffic. [SEC] reviews standard approaches from
the literature and proposes a fast, lightweight and decentralized
approach based on hash chains that can be applied to MAP-Me and fits
its design principles.
7. Acknowledgements
The authors would like to thank Giulio Grassi (UPMC/UCLA), Giovanni
Pau (UPMC/UCLA) and Xuan Zeng (UPMC/SystemX) for their contribution
to the work that has led to this document.
8. IANA Considerations
This memo includes no request to IANA.
9. References
9.1. Normative References
[RFC6301] Zhu, Z., Wakikawa, R., and L. Zhang, "A Survey of Mobility
Support in the Internet", RFC 6301, DOI 10.17487/RFC6301,
July 2011, <https://www.rfc-editor.org/info/rfc6301>.
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9.2. Informative References
[DATAPLANE]
J, ., A, ., A, ., B, ., M, ., and . S, "Ensuring
connectivity via data plane mechanisms.", 2013.
[MAPME] Auge, J., Carofiglio, G., Grassi, G., Muscariello, L.,
Pau, G., and X. Zeng, "MAP-Me: Managing Anchor-Less
Producer Mobility in Content-Centric Networks",
DOI 10.1109/tnsm.2018.2796720, IEEE Transactions on
Network and Service Management Vol. 15, pp. 596-610, June
2018, <https://doi.org/10.1109/tnsm.2018.2796720>.
[NLSR] Hoque, A., Amin, S., Alyyan, A., Zhang, B., Zhang, L., and
L. Wang, "NISR", DOI 10.1145/2491224.2491231, Proceedings
of the 3rd ACM SIGCOMM workshop on Information-centric
networking - ICN '13, 2013,
<https://doi.org/10.1145/2491224.2491231>.
[SEC] Compagno, A., Zeng, X., Muscariello, L., Carofiglio, G.,
and J. Auge, "Secure producer mobility in information-
centric network", DOI 10.1145/3125719.3125725, Proceedings
of the 4th ACM Conference on Information-
Centric Networking, September 2017,
<https://doi.org/10.1145/3125719.3125725>.
[SURVEY12] Ahlgren, B., Dannewitz, C., Imbrenda, C., Kutscher, D.,
and B. Ohlman, "A survey of information-centric
networking", DOI 10.1109/mcom.2012.6231276, IEEE
Communications Magazine Vol. 50, pp. 26-36, July 2012,
<https://doi.org/10.1109/mcom.2012.6231276>.
[SURVEY13] Tyson, G., Sastry, N., Rimac, I., Cuevas, R., and A.
Mauthe, "A survey of mobility in information-centric
networks", DOI 10.1145/2248361.2248363, Proceedings of the
1st ACM workshop on Emerging Name-Oriented Mobile
Networking Design - Architecture, Algorithms, and
Applications - NoM '12, 2012,
<https://doi.org/10.1145/2248361.2248363>.
[SURVEY14] Xylomenos, G., Ververidis, C., Siris, V., Fotiou, N.,
Tsilopoulos, C., Vasilakos, X., Katsaros, K., and G.
Polyzos, "A Survey of Information-Centric Networking
Research", DOI 10.1109/surv.2013.070813.00063, IEEE
Communications Surveys & Tutorials Vol. 16, pp. 1024-1049,
2014, <https://doi.org/10.1109/surv.2013.070813.00063>.
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[SURVEY16a]
Feng, B., Zhou, H., and Q. Xu, "Mobility support in Named
Data Networking: a survey", DOI 10.1186/s13638-016-0715-0,
EURASIP Journal on Wireless Communications and
Networking Vol. 2016, September 2016,
<https://doi.org/10.1186/s13638-016-0715-0>.
[SURVEY16b]
Zhang, Y., Afanasyev, A., Burke, J., and L. Zhang, "A
survey of mobility support in Named Data Networking",
DOI 10.1109/infcomw.2016.7562050, 2016 IEEE Conference on
Computer Communications Workshops (INFOCOM WKSHPS), April
2016, <https://doi.org/10.1109/infcomw.2016.7562050>.
[WLDR] Carofiglio, G., Muscariello, L., Papalini, M., Rozhnova,
N., and X. Zeng, "Leveraging ICN In-network Control for
Loss Detection and Recovery in Wireless Mobile networks",
DOI 10.1145/2984356.2984361, Proceedings of the 2016
conference on 3rd ACM Conference on Information-Centric
Networking - ACM-ICN '16, 2016,
<https://doi.org/10.1145/2984356.2984361>.
Authors' Addresses
Jordan Auge (editor)
Cisco Systems Inc.
11, rue Camille Desmoulins
92130 Issy-les-Moulineaux
France
Email: augjorda@cisco.com
Giovanna Carofiglio
Cisco Systems Inc.
11, rue Camille Desmoulins
92130 Issy-les-Moulineaux
France
Email: gcarofig@cisco.com
Luca Muscariello
Cisco Systems Inc.
11, rue Camille Desmoulins
92130 Issy-les-Moulineaux
France
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Email: lumuscar@cisco.com
Michele Papalini
Cisco Systems Inc.
11, rue Camille Desmoulins
92130 Issy-les-Moulineaux
France
Email: micpapal@cisco.com
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