inter-domain routing, ipv6, and network visualization

computer networks research group @ roma III university

inter-domain routing, ipv6, and network visualization

giuseppe di battista

maurizio patrignani

computer networks research group @ roma III university - namex 19 nov 04

main research topics• interdomain routing

– analysis of the route changes for the incoming traffic flows– location of the internet routing instabilities– modeling of bgp configurations and analysis of their stability– inference of the customer-provider relationships– study of the routing (a)symmetries– engineering of the incoming traffic flows– discovery of a large(r) as graph– integration and visualization of the irr info

• intradomain routing– ospf visualization– layer-3 discovery techniques

• ipv6– support for the ipv4-ipv6 transition– multi-homing methods

• network emulation– cheap and easy-to-configure test-beds for complex networks


analysis of the route changes for the incoming traffic flows

• development of a web service, called bgplay, visualizing the route changes of a prefix in a specific time window

• two running servers at– routing information service of the ripe ncc

(www.ris.ripe.net/bgplay/)– route views project of the oregon university

(www.routeviews.org)• each based on the corresponding repository of

bgp updates• an alpha version at roma III university with the

most recent features


bgplay query formspecify the prefix

(network) you want to monitor

specify an interval of time

select data sources


bgplay demo


location of the internet routing instabilities

• monitoring of the network from several vantage points– each vantage point stores the bgp updates

that are “visible” from its location

• related updates are grouped into “events”

• the causes of each event are (if possible) identified by studying the evolution of the routing over time


modeling of bgp configurations and analysis of their stability

• study of formal models for the description of bgp configurations and behaviors

• study of the effect of different time sequences of the events

• identification of possible routing instabilities

• routing stability vs forwarding stability– stability of the entire routing information base

vs stability of the best choice


inference of the customer-provider relationships

• a simple model accounting for customer-provider and peer-to-peer relationships only

• infer the types of relationship between autonomous systems by observing the as-paths associated with announcements– if sensible rules of thumb are followed by network

operators, each as-path is “valley free”

• if rules of thumb are followed by network operators, relationships can be efficiently inferred


inference of the customer-provider relationships

• if a set of relationships making all as-paths valley free does not exist– we prove that maximizing the number of

valley free as-paths is a hard problem– we propose heuristics for this problem that

outperform cutting-edge techniques described in literature


study of the routing (a)symmetries

• netviewer web service– prototype at www.dia.uniroma3.it/~compunet/

• having at disposal internal and external info shows routing asymmetries

• group prefixes into classes that have the same routing

• in cooperation with caspur and garr


example of routing classes

198.150.84.0198.150.85.0198.150.87.0

198.150.2.0 198.150.22.0 198.150.38.0 198.150.4.0 198.150.5.0 198.150.6.0 198.150.7.0 198.150.9.0

1st July 2003


example of asymmetric routing

1st July 2003

= 129.125.0.0/16

= 130.136.0.0/16


engineering of the incoming traffic flows

• even a limited control of the announcements propagation could be used to– balance traffic from the upstream providers– prefer reliable incoming paths– improve internal traffic flows

• engineering incoming traffic via prepending– Integer Linear Programming formulation– computational geometry perspective


discovery of a large(r) AS graph

• starting from the bgp updates collected by the ris or orv repositories a big picture of the internet can be obtained

• this picture can be enlarged by observing “unusual” bgp traffic – bgp updates with peculiar timings– bgp updates with peculiar content

• we can gain extra info by– observing unusual bgp updates– probing the network with unusual bgp updates

• for example setting up suitable beacons and observing echoes

• in cooperation with namex


integration and visualization of the irr info

• hermes service– available at www.dia.uniroma3.it/~hermes/

• handles a local relational database of routing information– downloads rpsl information from more than 50

databases that are individually operated by organizations such as verio, cable & wireless, merit, ripe ncc, apnic, arin, sprint, etc.

• through a java applet it is possible to navigate the repository and obtain information about the rpsl objects


integration and visualization of the irr info


ospf visualization

• polyphemous tool– downloadable from www.dia.uniroma3.it/~polyph/

• collects routing information using snmp and mibs• explores an ospf network at different levels of

abstraction– shows ospf areas an area border routers– shows routers and links inside each area– provides detailed info about areas, routers, interfaces.

• in cooperation with caspur


ospf visualization


layer-3 discovery techniques

• nethunter service– available at www.dia.uniroma3.it/~nethunt/

• exploits a collection of traceroute servers• explores the surroundings of an ip

interface or network by performing traceroutes from different vantage points

• uses a logic engine for inferring topologies– guess and check approach to asses whether

two interfaces belong to the same router


support for the ipv4-ipv6 transition

• techniques to detect, and collect information about, ipv6-in-ipv4 tunnels (mtu-discovery, dns, ip spoofing,…)

• discovered tunnels can be used as “vantage points” to launch third-party tunnel-discovery explorations, scaling up the discovery process

• wide experimentation– 6bone tunneled network, garr network, wide network, ripe ncc

network and ttm test-boxes• we assess to what extent 6bone registry information is

coherent with the actual network topology• we provide the first experimental results on the current

distribution of ipv6-in-ipv4 tunnels in the Internet• in cooperation with garr and ripe ncc


multi-homing methods

• hosts in a multi-homed as receive an ipv6 address from each upstream provider

• how to handle multiple ipv6 addresses?– need to take into account traffic loads– need to propagate information from the border

routers to the internal networks– need to swap ipv6 addresses without

dropping tcp connections


cheap and easy-to-configure test-beds for complex networks

• netkit (network emulator)– available at www.netkit.org

• a linux kernel may run as a user process (user mode linux)

• a network of linux virtual machines may run on a single host

• each linux may be configured to run routing daemons (zebra, bird, gated, routed, xorp, quagga,…)

• new configurations may be tested before being deployed • in cooperation with garr


concluding remarks

• a mixed theoretical-technical approach in all topics

• tight relationships with network operators– caspur, garr, namex, orv, ripe, …

• research-teaching coupling– univ. courses on comp. networks and courses

on specific technologies for companies and pa


thank you!

questions?

inter-domain routing, ipv6, and network visualization

Documents

routing asymmetriesengineering

interdomain routing

incoming traffic flowslocation

incoming traffic flowseven

route changes

tobalance traffic

network operators

paths valley free