Routing on Flat Labels Hauptseminar Innovative - - PowerPoint PPT Presentation

Lehrstuhl Netzarchitekturen und Netzdienste

Institut für Informatik Technische Universität München

Routing on Flat Labels

Hauptseminar Innovative Internet-Technologien und Mobilkommunikation Wintersemester 08/09 Benjamin Krinner

Routing on Flat Labels

2

Outline

• Basics
• Advantages of Routing on Flat Labels
• Preliminaries

– Intradomain – Interdomain

• Additional Routing Issues

– Routing Control – Enhanced Delivery Services – Security

• Outlook

Routing on Flat Labels

3

Basics

• Routing on Flat Labels

– Identity get rid of location → – No semantics flat namespace →

• Intradomain-Routing

– Routing within an autonomous system

• Interdomain-Routing

– Routing between autonomous systems

Routing on Flat Labels

4

Advantages of Routing on Flat Labels

• No new infrastructure

– No need for a seperate Name resolution system

• Simpler allocation

– Allocation of identities need only ensure uniqueness

• Fate-sharing

– Packet delivery does not depend on anything off the data path

• More appropriate access controls

– Network-level access controls can be applied to the identifier

Routing on Flat Labels

5

Preliminaries

• Identifiers (ID)

– self-certifying identifiers – host's or router's identity is tied to a public-private key pair – its identifier (ID) is a hash of its public key – Each host and router has a single, globally unique ID

• Source routes

– from one hosting router to another.

• Classes of Nodes

– Three classes of nodes:

• Routers
• Stable hosts (e.g. servers)
• Ephemeral hosts (e.g. home PCs)

Routing on Flat Labels

6

Preliminaries

• Source-Route Failure Detection

– To detect source route failures (like an underlying OSPF-like protocol) – Intra-domain:

• Finds paths to other hosting routers within the same AS

– Inter-domain:

• Maintains routes to external border routers whom the internal hosting routers

have pointers to

• Security

– Self-certifying identifiers help fend off attacks against ROFL mechanisms itself – Host must prove to the router cryptographically that it holds the appropriate private key – Auditing mechanisms (limit the number of IDs hosted by a router)

Routing on Flat Labels

7

Intradomain Preliminaries

• Joining

– New host a arrives its hosting router sets up a source route from → ida to its successor ID also contacts the hosting router for the predecessor ID to have it install a source route from it to ida

• Caching

– New source route routers along the path can cache the route (pointers to → various IDs)

• Routing

– Routing is greedy

Routing on Flat Labels

8

Intradomain Preliminaries

• Recovering

– In case of router failure neighboring routers inspect all their cached → pointers send tear-down messages → – In case of host failure(ID failure) router sends tear-down messages to → each successor and predecessor (of the ID) – To prevent the successor ring to partition into multiple pieces routers → locally perform a correctness check execute a partition-repair protocol →

• Ephemeral hosts

– Ephemeral host cannot serve as successor or predecessor to other Ids – They merely establish a path between themselves and their predecessor

Routing on Flat Labels

9

Intradomain Preliminaries

Failures

• Router failure:

– If a router R hosting several IDs goes down two things need to happen

• Each host connected to the router R discovers the outage (via session timeout)

and rejoin via an alternate router

Alternatively to prevent this it can join multiple routers during its initial join

• Every router connected to router R has a sorted list of routers that will be

connected in case of a failure of the router R

Routing on Flat Labels

10

Intradomain Preliminaries

• Host failure

– When host with ID ida fails the gateway router R will detect the failure → through a session timeout – Router R needs to inform all other routers with pointers to ida that it has failed

• Router R addresses all routers that are allowed to maintain cached state for ida

and holding a predecessor/successors of ida

Routing on Flat Labels

11

Intradomain Preliminaries

Link failure, no partition

• When a link is failed the router need not make any changes on behalf of

its resident IDs because the network map will find alternate paths Link failure, partition

• Successor pointers maintained by routers need to remerge into to

separate, consinstent namespaces

– Invalid pointers are torn down – Router attempts to repair these pointers

Routing on Flat Labels

12

Interdomain Preliminaries

• Constructing a global ring

– Model a simple hierarchical AS graph – Each AS X runs its own ROFL-ring (RR), RRx – To ensure connectivity between different ROFL-rings three phases have to be passed:

• AS X discovers its uphierarchiy graph Gx (consists of all ASes “above“ X in the

AS hierarchy)

• X perform a Canon-style recursive merging protocol
• They use proximity-based routing tables to reduce stretch

Routing on Flat Labels

13

Interdomain Preliminaries

• Joining

– New host a arrives in AS X (wants to be globally reachable) its hosting → router finds a successor and predecessor at each level of the G x sub- hierarchy hosting router then associates the successor and predecessor → pointer for ida with an AS-level source-route

• Routing

– Greedy Routing augmented with in-packet AS-level source-routes – A packet routed towards its destination is marked with an AS-level source route – Router receives a packet it uses the source-route to determine the route → to forward the packet

Routing on Flat Labels

14

Interdomain Preliminaries

• Recovering

– In case of router failure routers with pointers to the failed router are notified

• Pro-actively by neighbors of the failed router
• Discover the failure when forwarding a packet

– In case of host failure the router sends tear-down messages – In case of AS-level link failures the isolation property ensures that hosts in ASes X and Y can route to one another

• Handling Policies

– ROFL can handle peering and multi-homing relationships between ASes – Multi-homing links = backup links

Routing on Flat Labels

15

Additional Routing Issues - Routing Control

Inter-domain routing control

• ROFL's policy extensions support customer-provider, backup and

peering relationships

• Other policies can be handled Endpoint-based negotiation

– Source and destination nodes negotioate the path to be used

Routing on Flat Labels

16

Additional Routing Issues - Routing Control

Intra-domain routing control

• Interdomain design can be leveraged to deal with certain

intradomain policies

• e.g. a transit AS spread over multiple countries can create subrings

Routing on Flat Labels

17

Additional Routing Issues - Enhanced Delivery Services

Anycast

– Servers belonging to group G join with ID (G,x) – A host then route to (G,y), where y is set arbitrarily – Intermediate routers forward the packet reaching the first server in G for which the packet encounters a route

Multicast

– Host wishing to join the multicast group G sends an anycast request towards a nearby member of G – At each hop the message adds a pointer corresponding to the group pointing back along the reverse path – If the message interesects a router that is already part of the group the packet does not traverse any further

Routing on Flat Labels

18

Additional Routing Issues - Security

Default off

– Concerning security hosts should not by default be reachable from other hosts

• Ensuring hosts are only reachable from their hosting router

– The host can control pointer construction to limit which other hosts are allowed to reach it – Hosts explicitly have to register with their providers traffic to a host not → registered with its provider will be dropped

Routing on Flat Labels

19

Additional Routing Issues - Security

Capabilities

– A capability is a cryptographic token designating that a particular source is allowed to contact the destination – When a destination receives a route setup request it grants access according to its own policies

• Permission granted

path information and capability are returned to the source → , which it uses to communicate further with the destiantion

– Permission is cryptographically secured by the self-certifying identifier of the receiver

Routing on Flat Labels

20

Outlook

• This paper has not the solution

– Just initial stab at the challenge

• Scaling and efficiency are still far from ideal
• Revolutionary idea on how to seperate identity and location
• Interesting for the future to incorporate e.g. mobility

Routing on Flat Labels

21

Thank you

Routing on Flat Labels

22

Quellen

• M. Caesar, T. Condie, J. Kannan, K. Lakshminarayanan, I.Stoica, S. Shenker, ROFL: Routing on Flat Labels, ACM SIGCOMM, September 2006