cs 268: project suggestions ion stoica january 26, 2004
TRANSCRIPT
CS 268: Project Suggestions
Ion Stoica
January 26, 2004
Overview
Discuss 10 project suggestions- 5 related to i3
- 5 other projects
Legend: based on how well-defined projects are not necessary how difficult they are
- Well-defined projects (5)
- Less-defined project (3)
- You need to define project’s goals (2)
Need to send me a one page proposal by Feb 8
Project Related with Internet Indirection Infrastructure (i3)
Overview of i3 Suggestion 1: Transcoding Application Suggestion 2: Service Differentiation Suggestion 3: Migrate-able End-to-End Protocols Suggestion 4: Anonymous File Transfer Suggestion 5: Event Notification System
Goal
Provide seamless support for basic communication abstractions- Multicast
- Anycast
- End-host mobility
- Service composition
Key Observation
Many of current proposals use indirection, e.g., - Physical indirection point mobile IP
- Logical indirection point IP multicast
“Any problem in computer science can be solved by adding a layer of indirection”
Internet Indirection Infrastructure (i3)
Each packet is associated an identifier id To receive a packet with identifier id, receiver R
maintains a trigger (id, R) into the overlay network
Sender
id Rtrigger
iddata
Receiver (R)
iddata
Rdata
Service Model
API- sendPacket(p);
- insertTrigger(t);
- removeTrigger(t) // optional
Best-effort service model (like IP) Triggers periodically refreshed by end-hosts ID length: 256 bits
Mobility
Host just needs to update its trigger as it moves from one subnet to another
Sender
Receiver(R1)
Receiver(R2)
id R1id R2
iddata
Multicast
Receivers insert triggers with same identifier Can dynamically switch between multicast and unicast
Receiver (R1)id R1
Receiver (R2)
id R2
Sender
R1data
R2data
iddata
Anycast
Use longest prefix matching instead of exact matching- Prefix p: anycast group identifier
- Suffix si: encode application semantics, e.g., location
Sender
Receiver (R1)p|s1 R1
Receiver (R2)p|s2 R2
p|s3 R3
Receiver (R3)
R1datap|adata p|adata
Service Composition: Sender Initiated
Use a stack of IDs to encode sequence of operations to be performed on data path
Advantages- Don’t need to configure path
- Load balancing and robustness easy to achieve
SenderReceiver (R)
idT Tid R
Transcoder (T)
T,iddata
iddata
Rdata
idT,iddata idT,iddata
Service Composition: Receiver Initiated
Receiver can also specify the operations to be performed on data
Receiver (R)
id idF,R
Firewall (F)
Sender idF F
idF,Rdata
Rdata
F,Rdata
iddata iddata
Suggestion 1: Transcoding Application
Design a transcoding application - From one video format to another (e.g., MPEG
H.263)
- From one data format to another (e.g., HTML WML)
Transparent recovery- When one transcoder fails, another one takes over
without end-hosts being involved
Suggestion 2: Service Differentiation
Problem: flow isolation (UDP can kill TCP)
Solution outline:
TCP
UDP
TCP
UDP
Run RRApplication level
congestion control
Suggestion 3: Migrate-able End-to-End Protocols
Design a congestion control mechanism (e.g. TCP) such that it is possible to change the receiving machine in the middle of the transfer!
A and B open a connection (A receiver; B source) A changes to A’ B continues to send data to A’ without creating a
new connection Challenge: transparently transfer the receiver
state from A to A’
Suggestion 4: Anonymous File Sharing
IDs may be chosen such that not to reveal end-host identity
- E.g., pick random IDs
Sender doesn’t know the IP address of receiver You can simply use web to share files! Questions:
- Anonymous search engine
- Anonymity vs. performance
Suggestion 5: Event Notification System
Users specify events in which they are interested as a conjunction of attributes, e.g.,
- (stock=“msr”) and (share_price > 60)
- (source=“Berkeley”) and (destination=“North Lake Tahoe”) and (time < 3.5 hours)
Create an efficient delivery tree- Users with the same interest grouped under the same
tree
- Users in the same geographic region grouped under the same tree
Note: i3 not general enough to address this problem
DHTs Overview
Each data item and machine (node) in the system has associated a unique ID in a large ID space
Hash table like interface- put(id, data)
- data = get(id)
ID space is partitioned among nodes Data items are stored at the node responsible for
its ID
Example: Chord
Circular ID space [0..2m-1] Consider two consecutive nodes on the
ID circle with IDs N1 and N2, where N2 follows N1- Then node N2 is responsible for interval
(N1, N2] Node 35 inserts (37, data) Node 3 query data with ID 37
3
7
20
35
41
37 data
Chord circle
02m-1
Suggestion 6: Location Control in DHTs
Users do not have control over where data items are located
Advantages: - Users don’t need to know about individual nodes
- System can recover in case of failure without user involvement
Disadvantages:- Not efficient
- Enforces uniform trust model
Challenge: design a system in which users have “some” degree of control on where data items are located
- E.g., “I want my items to be located only on nodes in US”
Suggestion 7: Reduce (eliminate) Multicast State
In IP Multicast each router maintains state for each multicast group that has traffic traversing it
Problem: state hard to maintain and manage Extreme solution: maintain all receiver addresses in
each packet - Routers don’t need to maintain any state, but
- Packet headers can become very large huge overhead
Solution: design an algorithm in between- Maintain some state in routers and some in packets
Note: you can think either at the IP or application layer
Suggestion 8: Multipath Transport Protocols(due to Kevin Lai)
Motivation- Many paths between host A and B in current Internet
(multiple base stations, multihoming)
- Don’t know characteristics of paths
Which one to use?- Use all of them
- Must do so with congestion control
- For n independent paths, get n speedup
?
Suggestions 9: Overlay Routing
Assume- A network topology T
- A routing algorithm running on top of T
- You control a fraction f of nodes in T
Question:- How well can you approximate an “arbitrary” routing
metric as a function of f and topology T ?
Example: - T uses # of hops to implement shortest path
- You know delay distributions along links in T
- How well can you approximate lowest latency routing metric assuming a power-law topology and f = 10%?
Suggestion 10: Forwarding in Low Energy Wireless Networks
Assumptions- Each node is independently switching between ON and
OFF states
- Two nodes can communicate only when both of them are simultaneously ON
- A node stores a packet in transit until it finds the next hop ON
- Routing tables are known
Question:- What is the relationship between the fraction of time a
node is ON and the time to deliver a message and the amount of storage required by a node?
Next Step
You can either choose one of the projects we discussed during this lecture, or come up with your own
Pick your partner, and submit a one page proposal by February 8. The proposal needs to contain:
- The problem you are solving
- Your plan of attack with milestones and dates
- Any special resources you may need