DOCSLIB.ORG

Network Layer Implemented Anycast Load Balancing

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Network Layer Implemented Anycast Load Balancing Network layer implemented Anycast Load Balancing Ricardo Lopes Pereira Teresa Vaz˜ao IST, Inesc-ID IST, Inesc-ID [email protected] [email protected] Abstract only server availability, but also the network distance and conditions along the paths from client to server and vice- This paper presents a server selection method where the versa. This is also what routing protocols such as Open server selection is performed by the network, at the first Shortest Path First (OSPF) do, compute shortest paths. As- router from the client. This method, usable in networks un- signing each server the same anycast address [16] allows der single administrative control, combines network metrics each router to know the path towards the nearest server. (such as traffic or latency) with common server load bal- When clients use the anycast address to reach servers, the ancing metrics (such as load, CPU utilisation or response network layer will automatically forward packets to the time), allowing network conditions to be taken into account nearest server (according to the routing metrics) [9]. This when selecting the server which will handle the request. method is successfully being used today in the Internet to The performance of this technique was compared, by distribute User Datagram Protocol (UDP) queries by the means of simulations, to that of widely used techniques such Domain Name System (DNS) root servers [6]. as random, round robin and least loaded server selection. This paper presents a transparent load balancing tech- nique usable on networks under common administrative control, which aims at providing unmodified clients with 1 Introduction better reply times while maximising the total number of re- quests handled by the set of servers. This method, which was named Network layer implemented Anycast Load Bal- Despite the advent of the Personal Computers (PC) and ancing (NALB), combines network proximity and server distributed computing, the client/server model still plays load information in order to achieve dynamic load balanc- a major role today. Many applications, such as Database ing resorting to anycast addresses and link cost variation on servers and Web Services, remain centralised due to their already deployed routing protocols. This technique was val- nature. The ubiquity of the Internet or intranets, coupled idated by means of simulation using the HyperText Trans- with the emergence of the web browser as a human inter- fer Protocol (HTTP) protocol, although it may be applied face, also dictates that many applications are developed us- to other applications such as DNS, Simple Mail Transfer ing the web server centric paradigm. However, this cen- Protocol (SMTP) or proxy servers. tralised approach has its weaknesses, as it presents a single Section 2 details the anycast concept, its strengths and point of failure. The concentration of all clients on the same limitations. Section 3 presents the proposed load balanc- server may also result in slow response times due to server ing scheme, which was compared with others by means of overload or large network delays or congestion along the simulations, whose results are provided in section 4. The path from client to server. conclusions are presented in section 5. Replicating the application across several servers will eliminate the single point of failure. Server load can be mit- igated by placing the application in a set of servers located 2 IPAnycast in the same Local Area Network (LAN). Network latency and congestion may be avoided by placing servers across The anycast concept was introduced into IP networking a Wide Area Network (WAN), closer to the clients. The in [16], which defines it as: the best effortdeliveryof a data- two methods can be combined by spreading several clusters gram to at least one, and preferably only one, of the servers across a WAN. that accept datagrams for the anycast address. IPv6 is the For each of these approaches different load balancing first version of the IP protocol to support anycasting, albeit methods are used to distribute the clients’ requests [1]. with limitations: anycast addresses may only be assigned to WAN load balancing techniques may take into account, not routers, not hosts; and may only be used as the destination of a packets, never as the source [7]. anycast (SPRA) directs packets to the nearest server; it can Given several servers sharing the same anycast IP ad- be performed on small or confined networks using tradi- dress and a proper routing infrastructure in place, clients tional routing protocols as OSPF [18]. Multi-path routing should be directed to the nearest server (in number of hops distributes packets among all servers within the same dis- or other routing metric). tance. Multi-path or global scale deployment of single-path routing require specialised routing protocols [4,20]. 2.1 Current combined anycast load bal- ancing methods 2.3 Maintaining TCP connections Different research proposals appeared combining any- Stateful connections methods, such as TCP, expect end- cast load balancing methods. points to remain the same throughout the life-time of the Ticket based probing combines anycast with server load connection, But anycast routing does not ensure that packets information by sending probes to several anycast servers. from the same connectionwill always reach the same server. They reply indicating they status (load). The status infor- Routing tables may change due to topology changes or due mation combined with the reply time provides server and to the introduction or removal of anycast servers. Several network information which is used to select the server [3]. proposals address the lack of stateful transport support by This method, however, is not transparent, requiring clients anycast, either by adding support applications, modifying to be modified. Most importantly, it requires routers to be Transmission Control Protocol (TCP) or using IPv6 packet modified, for probe packets to reach several anycast servers. headers. These demands complicate its deployment in a legacy net- A supportapplication may be used to inform the client of work. the unicast address of an anycast server [20]. An UDP ser- Instead of leaving to the client the decision of which vice, running at each anycast server on a well known port server to use, [11] proposes to restore it to the network, by would receive UDP probe packets from the clients, which using an active network. Active networks use routers capa- would use the anycast address as destination. The server ble of running user supplied code on each packet. In this would respond with a UDP message indicating its unicast approach routers communicate with the servers, gathering address, which the client would then use to establish the load information, which may eventually be piggybacked on TCP connection. Should several anycast servers respond, traffic from the servers. This information is then used to only the first would be used. This method requires modifi- forward packets destined to the anycast server address. The cations to the clients and may not be used by legacy clients. router chooses the best server and changes the packet’s tar- Clients will also require a mechanism to know when a target get address from the anycast address to the best server’s uni- address is an anycast address. This method adds a round- cast address. When packets arrive in the opposite direction, trip to the connection establishment process. the source address is changed, from the server’s unicast ad- A client could also determine the servers unicast address dress to the anycast one. This solution requires an active by sending a ping (ICMP ECHO request) to the anycast ad- network, the development of a communication protocol be- dress. The server would then respond (ICMP ECHO reply) tween servers and routers and uses anycast addresses as the using its unicast address [13]. source of packets, which IPv6 disallows. Modifications to the TCP protocol would enable it to A different approach consists in the utilisation of rout- overcome anycast limitations [16]. Just like standard TCP, ing protocols which determine anycast routes using net- clients would send a SYN packet to the server’s anycast ad- work metrics as well as server state information [10]. This dress. However, the SYN-ACK response would arrive not method requires routers to collect and propagate server’s from the anycast address but from the server’s unicast ad- state information. Legacy routers would have to be up- dress, which would be used from then on. A different pro- graded to support these routing protocols. posal is to extend TCP’s tree way handshake to a five way handshake, creating a first phase where the unicast address 2.2 Anycast addressing and routing of the server is determined [20]. These methods do not re- quire the client to know, before hand, when the address is Anycast addresses can not be aggregated with other ad- an anycast one. Large scale TCP implementation substitu- dresses as they may be dispersed by several subnetworks tion, albeit simpler than legacy applications modification, and their world wide deploymentswould result in the explo- still represents a monumental endeavour. sion of the number of routing entries carried by each router. IPv6 packet extension headers may also be used to Nevertheless, they can be successfully used under sin- achieve the same goal [17]. The SYN-ACK response packet gle administrative control and several anycast intra-domain is extended with an header containing the anycast address, routing protocols have been proposed. Single-path routing while it originates on the server’s unicast address. The ex- tension header allows the client to perceive the original ad- routing protocols with server status information. dress as anycast and allows it to match the SYN-ACK to its TCP connection. The ensuing packets will use the unicast 3 Network layer implemented Anycast Load address.
Load more

Recommended publications
  • Performance Evaluation of TCP Multihoming for IPV6 Anycast Networks and Proxy Placement
    University of Central Florida STARS Electronic Theses and Dissertations, 2004-2019 2015 Performance Evaluation of TCP Multihoming for IPV6 Anycast Networks and Proxy Placement Raya Alsharfa University of Central Florida Part of the Electrical and Electronics Commons Find similar works at: https://stars.library.ucf.edu/etd University of Central Florida Libraries http://library.ucf.edu This Masters Thesis (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2004-2019 by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Alsharfa, Raya, "Performance Evaluation of TCP Multihoming for IPV6 Anycast Networks and Proxy Placement" (2015). Electronic Theses and Dissertations, 2004-2019. 1350. https://stars.library.ucf.edu/etd/1350 PERFORMANCE EVALUATION OF TCP MULTIHOMING FOR IPV6 ANYCAST NETWORKS AND PROXY PLACEMENT by RAYA MAJID ALSHARFA B.S. NAJAF TECHNICAL COLLEGE, 2010 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering. in the Department of Electrical Engineering and Computer Science in the College of Engineering and Computer Science at the University of Central Florida Orlando, Florida Fall Term 2015 Major Professor: Mostafa Bassiouni © 2015 Raya Majid Alsharfa ii ABSTRACT In this thesis, the impact of multihomed clients and multihomed proxy servers on the performance of modern networks is investigated. The network model used in our investigation integrates three main components: the new one-to-any Anycast communication paradigm that facilitates server replication, the next generation Internet Protocol Version 6 (IPv6) that offers larger address space for packet switched networks, and the emerging multihoming trend of connecting devices and smart phones to more than one Internet service provider thereby acquiring more than one IP address.
    [Show full text]
  • DNS Anycast for High Availability and Performance DNS Anycast Addressing for High Availability and by Timothy Rooney Performance Product Management Director
    White Paper DNS Anycast for High Availability and Performance DNS Anycast Addressing for High Availability and by Timothy Rooney Performance Product management director BT Diamond IP By Tim Rooney Director, Product Management BT Diamond IP www.btdiamondip.com DNS Anycast for High Availability and Performance By Tim Rooney, Director, Product Management Introduction We’ve all heard the mantra, “do more with less,” – for some of us to the point of numbness. But when it comes to mission-critical DNS name resolution services, any suggestion of skimping is likely to evoke defiance from those responsible for maintaining its availability and performance. One strategy, however, that can make the deployment of DNS services more efficient is the use of anycast addressing. This white paper shows how DNS servers can be deployed with anycast to achieve a number of benefits, including higher availability and resilience. Defining Anycast The term anycast refers to an IP address assigned to a set of interfaces (usually belonging to different nodes), any one of which can be the intended recipient. Anycast addresses are assigned from the same address space from which unicast addresses have been allocated. Thus, unlike private address space, one cannot visually differentiate a unicast address from an anycast address. An IP packet destined for an anycast address is routed to the nearest interface (according to routing table metrics) configured with the anycast address. The concept is that the sender doesn’t necessarily care which particular host, or in this case DNS server, receives the packet, just as long as one of those sharing the anycast address receives it.
    [Show full text]
  • Towards Passive Analysis of Anycast in Global Routing: Unintended Impact of Remote Peering
    Towards Passive Analysis of Anycast in Global Routing: Unintended Impact of Remote Peering Rui Bian Shuai Hao Haining Wang University of Delaware CAIDA / UC San Diego University of Delaware bianrui@udel:edu haos@caida:org hnw@udel:edu Amogh Dhamdere Alberto Dainotti Chase Cotton CAIDA / UC San Diego CAIDA / UC San Diego University of Delaware amogh@caida:org alberto@caida:org ccotton@udel:edu ABSTRACT adoption [8] or the efficiency in particular services like DNS[18]. Anycast has been widely adopted by today’s Internet services, in- Due to the insufficient distinctions between unicast and anycast cluding DNS, CDN, and DDoS protection, in which the same IP from the perspective of a routing table, the common method to address is announced from distributed locations and clients are di- identify anycast addresses is through active Internet-wide measure- rected to the topologically-nearest service replica. Prior research has ments. Cicalese et al. [8, 9] studied the enumeration and city-level focused on various aspects of anycast, either its usage in particular geolocation of anycast prefixes by using latency measurements services such as DNS or characterizing its adoption by Internet- based on the detection of speed-of-light violations. However, the wide active probing methods. In this paper, we first explore an latency of ping may not always reliably reflect the geographic dis- alternative approach to characterize anycast based on previously tance of two IP addresses [4, 34]. Also, active probing requires the collected global BGP routing information. Leveraging state-of-the- use of many vantage points to achieve the necessary coverage.
    [Show full text]
  • Crain-Haiti-Anycast-En.Pdf
    Anycasting the DNS John Crain Internet Corporation for Assigned Names and Numbers What is Anycast? ‣ “Anycast is a network addressing and routing scheme whereby data is routed to the "nearest" or "best" destination as viewed by the routing topology.” - Wikipedia ‣ unicast - IP address is a unique interface ‣ multicast - Multiple locations at same IP address all receiving packets. ‣ anycast - IP address points to multiple locations but only one visible. Limitations ‣ Because routing information can change! ‣ UDP protocols ‣ Short lived TCP sessions ‣ This sounds a lot like DNS packets :) ‣ Not good for longer TCP sessions ‣ Think of a web session that can last seconds or videostreaming that can last even longer! Why do it? ‣ Adds Capacity ‣ 2 x 100Mb is more than 1 x 100Mb ‣ Localizes trafc ‣ Means closer, hence faster replies ‣ During attacks it also localizes problems ‣ It’s FUN!!!! Is it hard? ‣ Not really but there are some considerations ‣ Managing the anycast instances takes some thought ‣ Need multiple IP address ranges... ‣ More on that..... Implementing Anycast Separate DNS server into it’s own network ‣ Get a dedicated routable /24 of IPv4 space and a range of IPv6 space ‣ Also get a dedicated Autonomous System Number (ASN) ‣ This is necessary for creating a unique routing entity ‣ ICANN L-ROOT (NET6-2001-500-3-1) 2001:0500:0003:0000:0000:0000:0000:0000 - 2001:0500:0003:FFFF:FFFF:FFFF:FFFF:FFFF ‣ ICANN L-ROOT (NET-199-7-83-0-1) 199.7.83.0 - 199.7.83.255 ‣ ASNumber: 20144 A name server ‣ Has an IP address on which it answers DNS queries.
    [Show full text]
  • Unicast Forwarding
    Unicast Forwarding • Unicast Forwarding, page 1 Unicast Forwarding The Enhanced Forwarding functionality consists of the following: • End Host Registration and Tracking: Leaf switch will intercept the ARP and DHCP packets and learns the IP to MAC binding for the host. In the case of virtualized environments, VDP may be used to track the VM moves. • End Host Route Distribution using BGP: MP-BGP is used within the Vinci fabric to distribute the IP reachability information across the leaf switches in the fabric. Route reflectors will be used for scalability purposes. • ARP and IPv6 ND Proxy: One of the goals of Vinci Enhanced forwarding is to eliminate flooding across the fabric. For this purpose, every leaf switch will act as a ARP/IPv6 ND proxy for all the hosts connected to the leaf switch. • Anycast Default Gateway: Leaf switches act as the default gateway for routing across subnets. All the leafs that handle a given subnet are configured with the same anycast IP address and MAC address. • Forwarding Behavior at Leaf switches: A fabric VLAN is allocated per tenant VRF in the Vinci fabric. BGP advertises the reachability of hosts attached to remote leafs to all the leaf nodes. Ingress leaf switch routes the traffic from the tenant VLAN to the egress leaf switch where the destination host is attached via the fabric VLAN. Egress leaf switch routes the traffic back to the tenant VLAN. This allow the platforms to optimize by scaling the FIB host route table without scaling the MAC address table. • Routing within the subnet: Leaf switch responds with the Anycast Default Gateway MAC to the ARP requests for hosts within the same subnet.
    [Show full text]
  • L-Root and Internet in LAC Mauricio Vergara Ereche | Qos Internet CEPAL | Oct 2015 Agenda
    L-Root and Internet in LAC Mauricio Vergara Ereche | QoS Internet CEPAL | Oct 2015 Agenda 1 2 3 What is L-Root LAC ICANN? Connectivity 4 5 Our model for Recommend deployment ations | 2 What is ICANN? What is a resilient and secure Internet? Quick Look at ICANN Overview ICANN is a global multi-stakeholder, private sector organization that manages Internet resources for the public benefit. It is best known for its role as technical coordinator of the Internet’s Domain Name System Mission To coordinate, at the overall level, the global Internet’s system of unique identifiers, and in particular to ensure the stable and secure operation of the Internet’s unique identifier system | 4 Supporting A Healthy, Resilient Internet | 5 SSR: Security, Stability and Resiliency Secure 1 Capacity to protect and prevent misuse of Internet Unique identifiers Stable Capacity to ensure that the system operates as expected, 2 and that users of the unique identifiers have confidence that the system operates as expected Resilient Capacity of the unique identifier system to effectively 3 withstand/tolerate/survive malicious attacks and other disruptive events without disruption or cessation of service | 6 L-Root DNS and Anycasting How DNS Works? Root Server 2 www.icann.org ? 1 3 4 8 .ORG Server 5 DNS Resolver (ISP) 6 9 7 www.icann.org ICANN.ORG Server | 8 What is L-Root? “L” is one of 13 independently operated root servers serving the DNS root zone ICANN DNS Engineering team operates L under the Autonomous System Number (ASN) AS20144 using the following
    [Show full text]
  • Implementation of DNS Anycast a Case Study
    Implementation of DNS Anycast a case study A. S. M. Shamim Reza | Md. Tawhidul Islam Bhuiyan Network Operation Center Link3 Technologies Ltd • Linux Geek • [~]$whoami Open Source Software Enthusiast | • EC-Council Certifed Security Analyst ASMShamimReza [email protected] [email protected] What is Anycast ? Anycast is a routing method in which incoming requests can be routed to a variety of diferent locations. The Journey • Why Anycast DNS – background history • Challenges – that we have faced • Deployment – what we have done • Confguration – the fun part • Performance & Security tuning – do’s & don’t Why Anycast DNS background history What we have faced ? 1. Existing DNS server OS version was about to obsolete 2. Resource utilization was always 95%-99% 3. When server was attacked with DDOS a. Query response delayed & most of the cases it stopped answering b. Unstable DNS service for user internet accesss 4. Log search was not administration friendly 5. No log options for Recursive query DNS Server – What we had Authoritative Recursive DNS Software resources Hardware resources CentOS 5 32 bit Core – 2 bind-utils-9.3.4-10.P1.el5 RAM – 4 GB ypbind-1.19-11.el5 HDD – Sata 7.2k RPM bind-libs-9.3.4-10.P1.el5 Why we choose Anycast • Because of the advantages – • users of an anycast service will always connect to the closest DNS server; This reduces latency, • if one server is being overly loaded, simply deploy another one in a location that would allow it to take some proportion of the overloaded server's requests; horizontal scaling. • We need to have 1 single IP for the Recursive DNS server all over Bangladesh.
    [Show full text]
  • AWS Certified Advanced Networking - Specialty Exam
    N E T 2 0 7 - R Understanding the basics of IPv6 networking on AWS Shakeel Ahmad Solutions Architect Amazon Web Services © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Agenda Why IPv6 Brief overview of the IPv6 protocol IPv6 in Amazon VPC IPv4 to IPv6 migration patterns Hands-on with IPv6 on AWS © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. IPv4 exhaustion IPv4 vs IPv6 address size IPv4: 32-bit / 4,294,967,296 addresses (~4.3 x 109) 11000000 00000000 00000010 00000001 IPv6: 128-bit / 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses (~3.4 x 1038) 0010000000000001 0000110110111000 0000111011000010 0000000000000000 0000000000000000 0000000000000000 0000000000000000 0000000000000001 © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. IPv4 vs IPv6 address types IPv4: Address types 1. Unicast 2. Broadcast 3. Multicast IPv6: Address types 1. Unicast 2. Multicast 3. Anycast IPv4 vs IPv6 address format IPv4: Dotted Decimal Notation + CIDR 192.168.0.1/24 127.0.0.1 IPv6: Colon-Separated Hextet Notation + CIDR 2001:0db8:0ec2:0000:0000:0000:0000:0001/64 0000:0000:0000:0000:0000:0000:0000:0001 2001:db8:ec2:0:0:0:0:1/64 0:0:0:0:0:0:0:1 2001:db8:ec2::1/64 ::1 © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved. Amazon VPC—dual-stack VPC Internet gateway IPv4: IPv6: Instance Public Subnet Amazon VPC—private subnet? NAT? VPC Egress-only internet gateway IPv4: IPv6: Instance X Private subnet Amazon VPC—IPv6 routing and more .
    [Show full text]
  • How Cloud-Based Dns Improves Digital Performance and Resilience
    Ebook: HOW CLOUD-BASED DNS IMPROVES DIGITAL PERFORMANCE AND RESILIENCE dyn.com 603 668 4998 150 Dowdyn.com Street, Mancheste603r, NH 668 031 499801 US A 150@dyn Dow Street, Manchester, NH 03101 USA @dyn High Availability DNS Reduces Downtime Risk and Improves End-User Experience How Redundant DNS Services Provide Resilience and Improve Application Performance In this guide you will learn: The critical role DNS plays in the user experience The difference between unicast and anycast-based Introduction DNS implementations DNS is the first link in your digital supply chain. Every user’s first interaction with your website begins with a series of DNS queries. Poor DNS The hidden costs, risks, and challenges performance can lead to slow page loads, dissatisfied customers, damage of managing your own on-premises to your brand, and lost business—so a “set it and forget it” approach to DNS infrastructure or using an DNS simply doesn’t work in the digital age. “add-on” DNS service from your ISP That’s why cloud-based, managed DNS services are now the norm for born- in-the-cloud companies—and increasingly for enterprise companies as well. The performance, reliability, They can enhance DNS performance, resiliency, and scalability, helping you and security advantages of a ensure superior user experience worldwide. This paper reviews the features cloud-based DNS service and benefits of a cloud-based DNS service. page 2 dyn.com @dyn Ebook | How Cloud-based DNS Improves Digital Performance and Resilience “Page size and complexity typically DNS Overview correlate to slower load times. The median page is 1945 KB in size and The Domain Name System (DNS) is a distributed internet database that contains 169 resource requests.
    [Show full text]
  • Routing-Independent Anycast for Ipv6 Content Delivery Networks
    ROUTING-INDEPENDENT ANYCAST FOR IPV6 CONTENT DELIVERY NETWORKS by YINHANG CHENG Submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Electrical Engineering and Computer Science CASE WESTERN RESERVE UNIVERSITY August 2019 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis of Yinhang Cheng candidate for the degree of Master of Science Committee Chair Michael Rabinovich Committee Member Michael Rabinovich Committee Member Vincenzo Liberatore Committee Member An Wang Date of Defense 06/21/2019 *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents List of Tables...................................................................................................................V List of Figures................................................................................................................ VI Abstract.......................................................................................................................VII 1. Introduction................................................................................................................8 2. Background...............................................................................................................11 2.1 DNS-based Request Routing in CDN................................................................11 2.2 IPv6 Mobility....................................................................................................13
    [Show full text]
  • Bidirectional Anycast/Unicast Probing (BAUP): Optimizing CDN Anycast
    Bidirectional Anycast/Unicast Probing (BAUP): Optimizing CDN Anycast Lan Wei∗ Marcel Floresy Harkeerat Bediy John Heidemann∗ ∗ USC/Information Sciences Institute y Verizon Digital Media Services fweilan, [email protected] fmarcel.flores, [email protected] Abstract—IP anycast is widely used today in Content Delivery between large latencies that are due to problems (say, a path Networks (CDNs) and for Domain Name System (DNS) to provide that misses a shorter route) from latency that is inherent efficient service to clients from multiple physical points-of- (for example, users connecting via satellite or over long presence (PoPs). Anycast depends on BGP routing to map users to PoPs, so anycast efficiency depends on both the CDN operator distances). Root causes are challenging to find because even and the routing policies of other ISPs. Detecting and diagnosing though measurement can provide latencies and paths, we inefficiency is challenging in this distributed environment. We do not know why problems occur. Finally, once problems propose Bidirectional Anycast/Unicast Probing (BAUP), a new have been identified (for example, a provider known to have approach that detects anycast routing problems by comparing frequent congestion), the CDN must determine solutions to anycast and unicast latencies. BAUP measures latency to help us identify problems experienced by clients, triggering traceroutes those problems. Solutions are not always possible and can to localize the cause and suggest opportunities for improvement. be difficult to determine, particularly when the problem is Evaluating BAUP on a large, commercial CDN, we show that multiple hops away from the CDN. problems happens to 1.59% of observers, and we find multiple Our first contribution is to design Bidirectional Any- opportunities to improve service.
    [Show full text]
  • 2526 Carnegie Mellon University Category: Standards Track S. Deering Cisco Systems, Inc
    Network Working Group D. Johnson Request for Comments: 2526 Carnegie Mellon University Category: Standards Track S. Deering Cisco Systems, Inc. March 1999 Reserved IPv6 Subnet Anycast Addresses Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. Abstract The IP Version 6 addressing architecture defines an "anycast" address as an IPv6 address that is assigned to one or more network interfaces (typically belonging to different nodes), with the property that a packet sent to an anycast address is routed to the "nearest" interface having that address, according to the routing protocols' measure of distance. This document defines a set of reserved anycast addresses within each subnet prefix, and lists the initial allocation of these reserved subnet anycast addresses. 1. Introduction IP Version 6 (IPv6) defines a new type of address, known as an "anycast" address, that allows a packet to be routed to one of a number of different nodes all responding to the same address [2, 3]. The anycast address may be assigned to one or more network interfaces (typically on different nodes), with the network delivering each packet addressed to this address to the "nearest" interface based on the notion of "distance" determined by the routing protocols in use. The uses of anycast addresses are still evolving, but such addresses offer the potential for a number of important services [5, 6].
    [Show full text]