NDN-Trace A A PATH TRA RACING UT UTILITY Y FOR R NDN NDN SIHAM - - PowerPoint PPT Presentation

NDN-Trace

A A PATH TRA RACING UT UTILITY Y FOR R NDN NDN

SIHAM KHOUSSI, DAVIDE PESAVENTO, LOTFI BENMOHAMED, ABDELLA BATTOU NA NATIONA ONAL L INS NSTITUTE OF OF STAND NDARDS DS AND ND TECHNOL NOLOG OGY (NI NIST)

NDN vs IP

IP traceroute

• Usually UDP or ICMP echo request
• Leverages ICMP “Time Exceeded” error
• Iterative process with gradually increasing TTL

Some NDN features make path tracing more challenging

• Multiple paths
• Forwarding strategies
• Content store

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NDN-Trace goals

1. Trace the path that an Interest for a given name would take

• One Interest, one Data, one path
• => single-path tracing

2. Explore path diversity in prefix reachability

• => multi-path tracing

q Measure round-trip time q Tracing can terminate at a cache (CS) or at a content producer q Traced name can be anything q No packet format or forwarder modifications

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Existing proposals

Contrace [draft-asaeda-icnrg-contrace-02] (2017)

• Custom CCNx packets for trace request/reply
• PIT entries are not consumed by returning data
• No RTT to intermediate routers

ICN Traceroute [draft-mastorakis-icnrg-icntraceroute-01] (2017)

• Iterative discovery with increasing HopLimit
• Introduces PathSteering header
• No mechanism that guarantees all paths are explored

Traceroute for NDN [shannigrahi-NDN-0055] (2017)

• Similar approach
• Does not measure RTTs
• No distinction between single- and multi-path
• Cannot trace content in caches

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NDN-Trace: components

Client application

• run by the user
• sends the initial trace request
• displays the discovered path(s) once the tracing session is completed

Trace daemon

• processes trace requests and replies
• registers the “/Trace” name prefix
• measures RTT

Forwarding strategy

• installed by the daemon for the “/Trace” prefix
• handles trace request forwarding
• performs Content Store lookups on behalf of the daemon

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NDN-Trace: naming

/Trace/<P1>/<P2>/<NameToTrace>/<TraceNonce>/<FaceId>

• P1: single- or multi-path tracing
• P2: termination condition (application/cache/any)
• TraceNonce: prevents aggregation of different tracing sessions in the same

PIT entry

• FaceId: id of the outgoing Interest, used to steer the request toward a

specific next hop

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NDN-Trace: operations

NFD 2 NFD 3

Client Daemon I1 Daemon

NFD 4

Daemon Daemon I2 I4 I3 I4 I3 I2 I1 I3 I4

NFD 1 NFD 2

Client Daemon D4 Daemon Daemon Daemon D3 D2 D1 D2 D1 D3 D4 D1

NFD 1

D2

NFD 3 NFD 4

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NDN-Trace: the tool

Public-domain C++ implementation

• Client program ndntrace
• Trace daemon ndntraced
• Uses ndn-cxx library version 0.5.1 (with one very minor modification)

We’re actively working on a second, improved version https://github.com/usnistgov/ndntrace

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Discussion and future work

Get rid of the custom forwarding strategy

• Add Content Store management API to NFD
• Leverage NDNLP’s NextHopFaceId field

Effect of regular strategies on chosen path

• An Interest for /P can be forwarded differently than /Trace/P
• Integrate tracing capabilities into existing strategies
• Composable strategies
• Integrate tracing into the forwarder itself

Naming scheme vs. packet field for tracing

• PathSteering TLVs, path labels, …
• How to reliably explore different paths?

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Backup slides

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Measuring RTT

!1 : time Interest arrives at trace daemon from NFD !2 : time Interest (for upstream) is sent to NFD %&

!3 : time Data arrives at trace daemon from NFD !4 : time Data (for downstream) is sent to NFD %&

0 1 & ,1 ,2 -1 ./,12

to/from -2

./,13 %/,12

4

.5,3 !3 !2 !6 !7 &

,3

1

,2

• 3
• 2

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