Docstoc

overlay-overview

Document Sample
overlay-overview Powered By Docstoc
					Overlay Networking Research
           @NTG


      Srinivasan Seetharaman
             Fall 2006
Overlay Networks
Overlay networks help overcome functionality
limitations of the Internet by forming a virtual
network on top of the IP network.

Overlay nodes collaborate to offer multiple services:
    Multicast (Ex: ESM, Overcast)
    Alternate paths (Ex: RON, Detour, X-Bone, Brocade)
    Customized forwarding (Ex: I3, Scattercast)
    QoS (Ex: OverQoS, SON)
    Name resolution, Intelligent routing…


                                                   NTG seminar – Fall 2006
Overlay Networks (contd.)
 Typical features:
    Overlay routing is independent of IP layer routing
     (Possibly with functionality overlap)

    End-system overlays (Ex: Skype), or
     Service overlays (Offer services to actual end-systems)

    Each Overlay link is actually an IP route between the two
     overlay nodes

    Each Overlay path is comprised of one or more Overlay
     links, inline with a certain objective

                                                          NTG seminar – Fall 2006
Example: Latency-Optimized paths
                   A           50ms
                                                  D



              20ms



                                 20ms
                                          C
        Relaying     B


 Potential for selfish behavior. Impact varies based on the
    percentage of overlay traffic
    scale of overlay networks

                                                      NTG seminar – Fall 2006
          What can go wrong?
                                              A
1.   Overlay routes can violate                                           D

     native layer polices
     - [Srini ICNP06]                    20ms



2.   Extra load on native links                     20ms
     causing bottleneck issues.    Relaying     B               C

     Serious issue when native
     layer wants load balance.
     - [Srini Ongoing]

3.   Failure detected by both layers and rerouted twice,
     with each rerouting disrupting the optimality of the previous.
     - [Srini Infocom06]



                                                           NTG seminar – Fall 2006
          What can go wrong? (contd.)
                                                  A
4.   Sub-optimal performance because
                                                                              D

     of lack of cooperation. Potentially
     a chicken-and-egg problem               20ms


     - [Srini Hotnets05]
                                                        20ms
                                                                     C
5.
                                       Relaying
     Topology (Nodes+Links)
                                                    B

     placement is tricky
     - [Jinliang Infocom06, Sridhar Ongoing, YongZhu Infocom06]

6.   Overlay routing can clash with TCP congestion control
     - [Ruomei Ongoing]




                                                               NTG seminar – Fall 2006
1. BGP Policy Violations
 Example violation over Planetlab and its benefit
 6.3ms lower latency = 10.48% gain




 Transit policy is violated in the above example. Harvard
 Univ pays its provider unnecessarily and unavoidably.


                                                    NTG seminar – Fall 2006
3. Dual Rerouting
                                                                                3           G   2
Consider a native link failure in CE                            A                                   I
   Only overlay link AE is affected.                                                    3
                                                                        2
   The native path AE is rerouted over F            OVERLAY
                                                                        4
                                                                                E
   (ACE → ACFDE)
                                                     NATIVE                                 G
                                                                           B
                                                                                                    I
                                                                A
             ∞                                                                      F
                                                                       C                        H
 Cost
                       Overlay                                              +
                       recovery: 8
                                                                                E           D


   Original: 2
                                Overlay                             Native
                              rerouting: 4                          Rerouting: 2



             Native       Native             Time             Native
             Failure     Recovery                             Repair

                                                                                        NTG seminar – Fall 2006
4. ESM-Friendly Native Network
               A
                                           D
New packet
 replication
  capability                                   Similar in
                                               spirit to
                                               REUNITE,
                B
                                    C          Packet
                                               reflection
  Reduce extra copies on some links
  No extra copies on each link
  Latency to reach C is less
            … If there were native layer support
                                               NTG seminar – Fall 2006
          What can go right?

0.   The services listed earlier, viz. QoS, Multicast, resilience,
     intelligent routing, security

    Improve performance of TCP using schemes like Overlay-TCP
     - [Pradnya Networking05]

    Improve services offered at the native layer by deploying
     them at the overlay layer (Ex: Name resolution)
     - [Sridhar Ongoing]

    Creating improved service-based architectures and end-
     system driven functionalities
     - Anyone interested?


                                                            NTG seminar – Fall 2006
References
 Jinliang Fan, Mostafa Ammar, "Dynamic Reconfiguration of Service Overlay
 Networks," IEEE INFOCOM, 2006. [PDF]

 Yong Zhu and M. Ammar, "Algorithms for assigning substrate network.
 resources to virtual network components," IEEE INFOCOM, 2006. [PDF]

 Pradnya Karbhari, M.Ammar, E. Zegura, "Optimizing End-to-End Throughput
 for Data Transfers on an Overlay-TCP Path", IFIP Networking, 2005. [PS]

 S. Seetharaman and M. Ammar, "Characterizing and Mitigating Inter-domain
 Policy Violations in Overlay Routes," IEEE ICNP, 2006. [PDF]

 S. Seetharaman and M. Ammar, "On the Interaction between Dynamic Routing
 in the Overlay and Native Layers," IEEE INFOCOM, 2006. [PDF]

 S. Seetharaman and M. Ammar, "Overlay-Friendly Native Network: A
 Contradiction in Terms?," ACM HOTNETS IV, 2005. [PDF]




                                                                 NTG seminar – Fall 2006

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:4
posted:12/13/2011
language:
pages:11