T-110.350 Computer Networks Spring 2005 1/29 T-110.350 Computer Networks: Routing Lecture II c Janne Lindqvist janne.lindqvist@tml.hut.fi 1/29
T-110.350 Computer Networks Spring 2005 2/29 Goals of the Set of Lectures The big picture Routing protocols distance vector (RIP) link state (OSPF) path vector (BGP) multicast Routing algorithms c Janne Lindqvist janne.lindqvist@tml.hut.fi 2/29
T-110.350 Computer Networks Spring 2005 3/29 Routing Protocols Interior Gateway Protocols (IGP) vs. Exterior Gateway Protocols (EGP) distance vector vs. link state vs. path vector c Janne Lindqvist janne.lindqvist@tml.hut.fi 3/29
T-110.350 Computer Networks Spring 2005 4/29 Autonomous Systems (AS) stub multihomed transit Today: 19201 autonomous systems c Janne Lindqvist janne.lindqvist@tml.hut.fi 4/29
T-110.350 Computer Networks Spring 2005 5/29 Why IGP and EGP? Why the classification: intradomain interdomain? Discuss! c Janne Lindqvist janne.lindqvist@tml.hut.fi 5/29
T-110.350 Computer Networks Spring 2005 6/29 Answer to Why IGP and EGP? If every AS had only two routers. It would mean 38402 routers in the Internet. Impossible with distance vector and link state protocols We need a divided routing scheme. c Janne Lindqvist janne.lindqvist@tml.hut.fi 6/29
T-110.350 Computer Networks Spring 2005 7/29 Policy Routing Route preferences: do not use path that goes through AS 12 Which destinations are reported to which neighbors Path editing Practical examples university networks vs. corporate networks traffic originated and ending in Canada must not leave Canada c Janne Lindqvist janne.lindqvist@tml.hut.fi 7/29
T-110.350 Computer Networks Spring 2005 8/29 Top-level Internet Routing peering points Finland, two Ethernet switches FICIX1 Espoo, Otaniemi FICIX2 Helsinki, Pasila 1 or 10 Gigabit Ethernet c Janne Lindqvist janne.lindqvist@tml.hut.fi 8/29
T-110.350 Computer Networks Spring 2005 9/29 Routing Protocols Interior Gateway Protocols (IGP) vs. Exterior Gateway Protocols (EGP) distance vector vs. link state vs. path vector c Janne Lindqvist janne.lindqvist@tml.hut.fi 9/29
T-110.350 Computer Networks Spring 2005 10/29 Border Gateway Protocol (BGP-4) Border routers BGP speakers Used between autonomous systems Provides reachability and path information TCP as transport c Janne Lindqvist janne.lindqvist@tml.hut.fi 10/29
T-110.350 Computer Networks Spring 2005 11/29 BGP-4 Message Types Message Types 1 OPEN 2 UPDATE 3 NOTIFICATION 4 KEEPALIVE c Janne Lindqvist janne.lindqvist@tml.hut.fi 11/29
T-110.350 Computer Networks Spring 2005 12/29 BGP-4 OPEN Message Version AS number Hold Time BGP Identifier: IP address Parameters Used to initialize communication c Janne Lindqvist janne.lindqvist@tml.hut.fi 12/29
T-110.350 Computer Networks Spring 2005 13/29 BGP-4 UPDATE Message List of destinations to be removed. List of new available destinations and paths to them. Information from the receiver s perspective. c Janne Lindqvist janne.lindqvist@tml.hut.fi 13/29
T-110.350 Computer Networks Spring 2005 14/29 BGP-4 Why Paths? Why UPDATE message contains path information? Discuss! c Janne Lindqvist janne.lindqvist@tml.hut.fi 14/29
T-110.350 Computer Networks Spring 2005 15/29 Answer to BGP-4 Why paths? Detect loops Policy routing However, cannot be used to deduce the optimal route. c Janne Lindqvist janne.lindqvist@tml.hut.fi 15/29
T-110.350 Computer Networks Spring 2005 16/29 BGP-4 KEEPALIVE Message For testing reachability. Sending interval should be 1/3 of the hold timer. c Janne Lindqvist janne.lindqvist@tml.hut.fi 16/29
T-110.350 Computer Networks Spring 2005 17/29 BGP-4 NOTIFICATION Message For error reporting AS routing loop Hold time unacceptable etc. c Janne Lindqvist janne.lindqvist@tml.hut.fi 17/29
T-110.350 Computer Networks Spring 2005 18/29 To Make Things Not Simple intradomain: I-BGP interdomain: E-BGP c Janne Lindqvist janne.lindqvist@tml.hut.fi 18/29
T-110.350 Computer Networks Spring 2005 19/29 BGP Security misconfigurations e.g. a route that should have been filtered is exported e.g. October 2003 WorldCom s internal routers crashed attacks c Janne Lindqvist janne.lindqvist@tml.hut.fi 19/29
T-110.350 Computer Networks Spring 2005 20/29 BGP Security No integrity, freshness or authentication for messages. No validation of AS authority for reachability information. No validation of path attribtues announced. c Janne Lindqvist janne.lindqvist@tml.hut.fi 20/29
T-110.350 Computer Networks Spring 2005 21/29 Attacks Against BGP Eavesdropping Replay Messsage insertion Message deletion Message modification Man-in-the-middle Denial of service c Janne Lindqvist janne.lindqvist@tml.hut.fi 21/29
T-110.350 Computer Networks Spring 2005 22/29 Damage from Attacks starvation network congestion and delay blackhole looping eavesdrop cut and partition churn and instability resource exhaustion c Janne Lindqvist janne.lindqvist@tml.hut.fi 22/29
T-110.350 Computer Networks Spring 2005 23/29 Protection from Attacks TCP MD5 option filtering (S-BGP?) c Janne Lindqvist janne.lindqvist@tml.hut.fi 23/29
T-110.350 Computer Networks Spring 2005 24/29 Functions of IP Address unicast address interface identifier (socket binds to IP) topological locator (routing) multicast address group identifier c Janne Lindqvist janne.lindqvist@tml.hut.fi 24/29
T-110.350 Computer Networks Spring 2005 25/29 Multicast in Theory Routers use multicast routing protocols to establish connectivity across Internet. Hosts tell routers that they want to receive from group G i. Any host can send to the group. Sending and receiving is simple by socket APIs. bandwidth-efficient group communication c Janne Lindqvist janne.lindqvist@tml.hut.fi 25/29
T-110.350 Computer Networks Spring 2005 26/29 Multicast Routing Protocols flooding source-tree core-tree mesh hybrid Everyone has a favorite protocol (including me!) c Janne Lindqvist janne.lindqvist@tml.hut.fi 26/29
T-110.350 Computer Networks Spring 2005 27/29 The Dichotomy Revisited intradomain Distance Vector Multicast Routing Protocol (DVMRP) Multicast Extensions to OSPF (MOSPF) Protocol Independent Multicast (PIM-SM) (PIM-DM) interdomain Multicast Source Discovery Protocol (MSDP) Border Gateway Multicast Protocol (BGMP) c Janne Lindqvist janne.lindqvist@tml.hut.fi 27/29
T-110.350 Computer Networks Spring 2005 28/29 The Big Picture Default route in a host. OSPF in the access network in an AS. BGP between ASes. And additionally PIM and MBONE. c Janne Lindqvist janne.lindqvist@tml.hut.fi 28/29
T-110.350 Computer Networks Spring 2005 29/29 That s All Questions? c Janne Lindqvist janne.lindqvist@tml.hut.fi 29/29