CSEE W4140 Networking Laboratory Lecture 12: Review Jong Yul Kim

Annoucements  Visit to TelioSonera’s NY POP Meet in front of Broadway and 116 th st main gate at starting time. Wednesday group: 1 pm Friday group: 10 am Can you join the Friday group?

ICANN  Internet Corporation for Assigned Names and Numbers

IANA  Is run by ICANN  Provides global coordination of Domain names (manages root) IP addresses AS numbers Protocol assignments

Registry Listings from ICANN Registry Listing.com1985UnsponsoredUnrestricted (but intended for commercial registrants) VeriSign, Inc. Registry Customer Service Registry Customer Service VeriSign Naming Services Ridgetop Circle Dulles, Virginia United States Tel : Fax: grs.com grs.com.edu1985SponsoredUnited States educational institutions EDUCAUSE Becky Granger Becky Granger EDUCAUSE 4772 Walnut Street, Suite 206 Boulder, Colorado United States Tel: Fax: edudomain edudomain TLDIntroduced Sponsored/ Unsponsored Purpose Sponsor/ Operator Contact.net 1985UnsponsoredUnrestricted (but intended for network providers, etc.) VeriSign, Inc. Registry Customer Service Registry Customer Service VeriSign Naming Services Ridgetop Circle Dulles, Virginia United States Tel: Fax: grs.com grs.com

Regional Internet Registries (RIRs)  Registration and management of IP address is done by Regional Internet Registries (RIRs)  Where do RIRs get their addresses from: IANA maintains a high-level registry that distributes large blocks to RIRs  RIR are administer allocation of: IPv4 address blocks IPv6 address blocks Autonomous system (AS) numbers

Regional Internet Registries (RIRs)

Tiered hierarchy of ISPs

Tier-1 ISPs  Tier-1 ISPs form the backbone of the Internet  Directly connected to each other for free: this is called peering.  Tier-2 ISPs and other networks connect to them for a fee: this is called transit.  International presence NameAS # AT&T7018 Global Crossing3549 Level 3 Communications 3356 NTT Communications2914 Qwest209 Sprint1239 Tata Communications6453 Verizon Business701 SAVVIS3561 TeliaSonera IC1299

What happens if Tier-1 ISPs fight each other?  Excerpts from “Sprint, Cogent in Peering Feud” by Karl Bode as published in dslreports.com.Sprint, Cogent in Peering Feud “A high profile dispute with Swedish telecom operator Telia in March cut off access to vast swaths of Europe.” “The latest fight came last night, when Cogent announced that Sprint pulled the plug on their connection with the Cogent network, impacting a significant amount of both URLs and broadband customers.”

Point-of-Presence (POP)  A location where ISPs interconnect with each other.  Usually houses a group of routers and switches that are shared among the ISPs.  Also known as Internet Exchange Points (IXP)

Routing Protocols  BGP for interdomain routing  RIP and OSPF for intradomain routing RIP is a distance vector protocol. Count-to-infinity is a problem. There are ways to deal with the problem. OSPF is a link state protocol. All routers have the same routing information. Unless they are divided into two-level hierarchy called areas.

LAN and switches  In setting up a LAN, you can use routers, hubs, and switches. Routers vs. switches Hubs vs. switches  Switches have nice properties. Plug-and-play through learning algorithm Spanning Tree Protocol to avoid loops

IP addressing and subnets  IP addresses have two parts: prefix and host. (CIDR notation: /24) Prefixes are used by routers to forward packets to the correct destination  Subnets Are divided by routers and hosts. Every machine in a subnet uses the same prefix. What happens if a machine’s netmask is different from the subnet’s prefix?

ARP  ARP is used to find the MAC address of the machine that uses a particular IP address.  ARP is used within a subnet. Unless a router uses proxy ARP to forward ARP requests to another subnet.  There are many other uses of ARP. IP conflict detection RARP for IP address configuration

NAT and DHCP  NAT is an outcome of the shortage of IPv4 addresses. But they can be used in many different applications, e.g. support migration between service providers.  NAT can be problematic for some applications.  DHCP is used to configure hosts within a subnet automatically. Relays can be used to traverse subnets.

SNMP  SNMP is used for network management.  The information objects are structured as a tree. (OID reflects the tree structure.)  Four parts: MIBs, SMI, the protocol, and security.

Homework  No prelabs due this Friday  Lab report 9 due next week by the normal dates