1. CS 268: Lecture 25 Indirection
Ion Stoica
Computer Science Division
Department of Electrical Engineering and Computer Sciences
University of California, Berkeley
Berkeley, CA

2. Indirection is Everywhere!
DNS Server
foo.org IPfoo
Home Agent
IPhome IPmobile
“foo.org”
(IPhome,data)
IPfoo
(IPmobile,data)
(IPfoot,data)
IPfoo
DNS
IPmofile
Mobile IP
NAT Box
IPnat:Pnat IPdst:Pdst
(IPM,data)
(IPnat:Pnat,data)
Internet
(IPMIPR1)
(IPMIPR2)
(IPdst:Pdst,data)
(IPR1,data)
(IPR2,data)
IPdst
NAT
IPR1
IPR2
IP Multicast

3. Why Indirection? Decouple sender behavior from receiver behavior
Receiver movements and address changes transparent to sender
Changes in the number of receivers, transparent to sender …

4. Discussion Control Resolution
Indirection point  point where control is transferred from sender to receiver
Translation/forwarding entry usually controlled by receiver
Resolution
Early binding (e.g., DNS, SIP, HIP)
Late binding (e.g., Mobile IP, NAT,IP multicast, IP anycast)

5. End-host Empowerment
Both the sender and receiver should be able to explicitly control the service-path
Note: multiple indirection points possible
Internet
Application
Layer
Service (ALS) 1
ALS 2
ALS 3
ALS 4
Receiver
Indirection point
(tussle boundary)
Sender
sender control
receiver control

6. Realization: i3 vs DOA i3 Internet Internet DOA ALS 1 (S1) ALS 2 (S2)
([idS1,idR], data)
idR [idS2,R]
ids1 S1
idS2 S2
Internet
ALS 1 (S1) R
([idS1,idS2], data)
idS2 idR
idS1 S1
idS2 S2
idS1 S1
ALS 2 (S2)
idS2 S2
idR R
idR
Name resolution infrastructure (e.g., OpenDHT)
DOA

7. Discussion: DOA vs. HIP vs. i3 (1/2)
Naming: Flat ID space
DOA: two levels of IDs
EID: end-host IDs
SID: service IDs
Resolution: (SIDEID); (EIDIPaddr)
HIP
HIT: host identity tag
Resolution: (HITIPaddr) i3
ID: identifies “anything”
Resolution: (ID[IPaddr:Port]), where [IPaddr:Port] represents de-multiplexer

8. Discussion: DOA vs. HIP vs. i3 (2/2)
Resolution:
HIP and DOA: early binding
i3 : late binding:
Lookup & Forwarding
i3: combines lookup & forwarding infrastructure
Degenerates to a lookup infrastructure when shortcuts are used
DOA: forwarding state at ALSes