UDL On-link Scalability Kotaro Kataoka Keio University

Outline How many nodes can a single UDL handle? How do we improve on-link scalability? –Tune parameters on existing protocols –Provide new systems Address Resolution on large scale UDLs

Background Broadcast Media as Internet Infrastructure –Huge number of subscribers –Unidirectional links + Feedback BDL What will happen there?

Definition of Scalability Number of nodes which a link can accommodate –Rate of control traffic against available bandwidth Control Traffic –IPv6 Address Auto-configuration (RS, ND) –Multicast Group Management (MLD) –Unicast / Multicast Routing Protocols –Ack / Nack / And more… Data Traffic –Many types of traffic

Possible Service Traffic (1/1) Internet Host Router External Node External Node P1 P2 P5? P3 P4

Possible Service Traffic (2/2) 1.Multicast from an external (Internet) node to subscriber nodes 2.Unicast between a subscriber node and an external (Internet) node 3.Multicast from a subscriber node to external (Internet) nodes 4.Multicast from a subscriber node to subscriber (on-link) nodes 5.Unicast between subscriber (on-link) nodes Priority Probability

Focus of Research: IPv6 Problem –Bandwidth consumption on UDL Approach / Solution –Tune back-off timers on ICMPv6 –Proxy Filtering Approach BDL Approach

Problem Analysis Evaluate how many hosts a single UDL can handle without any tuning / new system on the link Scenarios –Static (stable on changes on the network) No node up/down, No node join/leave, No UDL up/down –Dynamic Nodes get up/down Nodes get join/leave (multicast) UDL gets up/down How do we evaluate on-link scalability? –Calculation Check parameters from RFCs Mathematical Model –Simulation Omnet++ NS2? Make by myself? –Emulation Xen? Experiment on AI3 UDL

Steps Step1: Simple Leaf Network (LAN) –Address Auto-configuration –Manipulation of Neighbor Cache and Prefix Step2: Enable Multicast Services –Multicast Group Management Step3: Enable Routing Protocols –Unicast / Multiast

Related RFCs for Initial Discussion RFC4294: IPv6 Node Requirements –RFC2461: Neighbor Discovery for IP Version 6 (IPv6) –RFC2462: IPv6 Stateless Address Autoconfiguration –RFC2710: Multicast Listerner Discovery To simplify the situation… –Scenario for the first step

Steps to establish IPv6 communication on the links Stateless Address Autoconfiguration –Link-Local Addresses Creation of Link-Local Addresses Duplicate Address Detection –Global Addresses Router Solicitation Router Advertisement Creation of Global Addresses (Duplicate Address Detection) Maintenance of neighbor cache on each node –Several Scenarios to examin in a step-by-step manner Maintenance of prefix on the link –Router Advertisement

Calculation? How much does control data flows on the UDL? Bandwidth Consumption –# of nodes –Packet size of each message and frequency

Simple Scenario Every host is communicating only with non-link-local nodes –RAs from a Router –Neighbor Solicitation to from every host to Default Router on expiry of Neighbor Cache and its reverse case –Neighbor Advertisement to from Default Router to every host as the answer for Neighbor Solicitation and its reverse case Internet Host Router External Node External Node P2

Calculation for Simple Scenario Total amount of control data which flows on the UDL is… NH: Number of Hosts LNS: Length of Neighbor Solicitation LNA: Length of Neighbor Advertisement LRA: Length of Router Advertisement TR: Time duration during which nodes recognize that the other nodes are reachable on the link (Default: 30 sec) IRA: Interval of RA (Default: 600sec)

Methods for Designing Solutions Solutions? –Filtering approach –Reverse UDL approach Evaluation would be done by same method of problem analysis

Filtering Approach UDL Feed Bridge IP Encapsulater Router Internet (BDL) Internet (BDL) UDL DAD Proxy UDL Receiver UDL Router Advertisement with Short Interval Suppressed Router Solicitation Neighbor Solicitation for DAD Filtered Neighbor Solicitation for DAD

Reverse UDL Approach Receiver nodes advertise their BDL IP address which are mapped to UDL IP address Specific traffics (protocols) go to BDL Data Band via UDL Control Band via BDL Control Data UDL Receivers UDL Feed

Future Work / Directions Have to do many things... –Define communications models (scenarios) on UDL –Analyze scalability for other scenarios –Implement scenarios in the simulator –Design and Implement the approach to improve scalability on simulator –Move into the real world

Comments?

Materials

What a router has to maintain on an idle network on a stable link Unsolicited (Periodic) Router Advertisement –1 per 600sec (Default MAX Interval) Solicited (On-demand) Router Advertisement –Active network only…

analysis framework

Road Map

Control Traffic on an Active (non-link- local only) Network on a Stable Link Active (non-link-local only)? –Every host is communicating only with non-link-local nodes RAs from a Router Neighbor Solicitation to from every host to Default Router on expiry of Neighbor Cache and its reverse case Neighbor Advertisement to from Default Router to every host as the answer for Neighbor Solicitation and its reverse case

For neighboring routers, reachability means that packets sent by a node's IP layer are delivered to the router's IP layer, and the router is indeed forwarding packets (i.e., it is configured as a router, not a host) For hosts, reachability means that packets sent by a node's IP layer are delivered to the neighbor host's IP layer

– IP

RFCs for IPv6 Infrastructure Internet Protocol Version 6 –RFC 2460 Neighbor Discovery for IPv6: RFC2461 ICMP for the Internet Protocol Version 6 (IPv6) - RFC 2463 Multicast Listener Discovery (MLD) for IPv6 - RFC

Sirokuma-sans comment Two different themes –UDL scalability (ARP, Broadcast Protocols could work or not with many hosts?) –Time from network down to recovery Recovery time depens on many technologies from L2~L3 –Terrestrial performance –Check OUR SITUATION ONLY –Use Starbet

On-going work Omnet++ Tutorial –IP + IPv6 Suite Install and start to touch What I want to present at AI3 Meeting –Simple calculation on link scalability –Simple simulation of large-scale ethernet BCMA with delay tuning to emulate UDL –Narrow band –Long delay IPv6 nodes on UDL

evaluate –Estimate number of packet Expire time of neighbor cache on each IPv6 node RA interval –On-link – Number of node dependent independent –ICMPv6 Routing Protocol – Hello Interval Timer Implementation Dependent RFC –ARP Cache 30 –Adhoc Method

Hosts / Routers Hosts need –Maintain Neighbor Cache Routers need to –Maintain Neighbor Cache –Issue Router Advertisement

UDL Neighbor Discovery Address Autoconfiguration

10. PROTOCOL CONSTANTS Router constants: MAX_INITIAL_RTR_ADVERT_INTERVAL 16 seconds MAX_INITIAL_RTR_ADVERTISEMENTS 3 transmissions MAX_FINAL_RTR_ADVERTISEMENTS 3 transmissions MIN_DELAY_BETWEEN_RAS 3 seconds MAX_RA_DELAY_TIME.5 seconds Host constants: MAX_RTR_SOLICITATION_DELAY 1 second RTR_SOLICITATION_INTERVAL 4 seconds MAX_RTR_SOLICITATIONS 3 transmissions Node constants: MAX_MULTICAST_SOLICIT 3 transmissions MAX_UNICAST_SOLICIT 3 transmissions MAX_ANYCAST_DELAY_TIME 1 second MAX_NEIGHBOR_ADVERTISEMENT 3 transmissions REACHABLE_TIME 30,000 milliseconds RETRANS_TIMER 1,000 milliseconds DELAY_FIRST_PROBE_TIME 5 seconds MIN_RANDOM_FACTOR.5 MAX_RANDOM_FACTOR 1.5 Additional protocol constants are defined with the message formats in Section 4.

Scenarios Node definition (Make problems for each type clear) –Router (Host + Forwarding capability) –Host (End node) –Router + Host Type of Traffic (Services) on UDL –See next page

What nodes have to maintain on an idle network on a stable link Neighbor Cache –Life time for each cache entry is 30sec Send Neighbor Solicitation to Default Router on expiry Send Neighbor Advertisement to Default Router on request Destination Cache –Maybe vacant on an idle network –As a result of communication, this cache is maintained Prefix List –Learn from Router Advertisement Default Router List –Learn from Router Advertisement –Associated with Neighbor Cache

Very simple scenario Stable Link –No New Host –No Packet Loss –No Link Down / UP Traffic –Idle network (no traffic) as first step –Active network as second step (Multicast from Router)? Some conditions affect behavior of hosts

Calculation? How much does control data flows on the UDL? Bandwidth Consumption –# of nodes –duration –Packet size and frequency Steady State –Neigbor cache 30 Transient State –Node UP/DOWN – 10 1 Up/Down 2 Generalization