CMPE 257: Wireless and Mobile Networking Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 8 CMPE 257 Winter'11 1
Announcements: Student presentations: Security: Jim. Seth: security in sensor networks. Chris: security at the MAC layer. DTNs: Phillip. Rance. Mobility management: Tyler. Niosha. Energy management: Mohamed. Hybrid networks: Gregg. CMPE 257 Winter'11 2
Student Presentations Feb 28: Mobility management: Tyler and Niosha. March 2: DTNs: Philip and Rance. March 7: Hybrid networks: Gregg. Energy management: Mohamed. March 9: Security: Jim. March 14: Security: Chris and and Seth. CMPE 257 Winter'11 3
Today Wireless internetworking. CMPE 257 Winter'11 4
Wireless Internetworking Extension of Internet services to wireless/mobile users. Challenges? Wireless medium. Node mobility. TCP/IP stack. CMPE 257 Winter'11 5
Mobility IP assumes fixed nodes. Hierarchical addresses. IP address = network number+host number. IP address uniquely identifies host s PoA. Host must attach to network specified by its IP address to send/receive datagrams. But what if nodes move? Change address? How about packets destined to them? CMPE 257 Winter'11 6
Mobile IP Addresses redirection. Manages mobility at the IP layer. Hides mobility from upper layers. CMPE 257 Winter'11 7
Mobile IP: Goals Nodes can receive datagrams no matter where they attach to the Internet. IMHP (Internet Mobile Host Protocol) as Mobile IP precursor. CMPE 257 Winter'11 8
Last-hop Mobility Mobile IP is the Internet standard for lasthop mobility support in IP networks (RFC 2290). How do we deliver IP packets when the endpoints move? Mobile host must be able to communicate after changing its link-layer point-of-attachment. Mobile host must be able to communicate using its permanent (home) IP address. CMPE 257 Winter'11 9
Mobile IP: Design Issues Issues: Impact on IP addressing. Impact on routing. Impact on higher layers. Key design considerations: Scale. Compatibility. Transparency. CMPE 257 Winter'11 10
Terminology Home Agent (HA) Foreign Agent (FA) HN CH Mobile Host (MH) CMPE 257 Winter'11 11
Terminology (Cont d) Similar to cellular. Mobile Node (MN or MH): node changing its PoA. Correspondent Host (CH). Home Network (HN) and Foreign Network (FN). CMPE 257 Winter'11 12
Terminology (Cont d) Mobility Agents: Home Agent (HA): router on MN s HN that tunnels datagrams to MH when away and keeps MH s current location info. Foreign Agent (FA): router on foreign network; delivers datagrmas to MH while on FN. Home Address (HoA) and Care-of Address (CoA): HoA: MH s permanent address on HN. CoA: MH s temporary address on FN. CMPE 257 Winter'11 13
Care of Address FA-based. MN s address is its current FA s address. FN-based. Locally-assigned address in FN. E.g., DHCP address. What s the difference? CMPE 257 Winter'11 14
Mobile-IP: Basic Operation MH normally uses its home address HoA. When MH visits a foreign network, Registration with FA. Discover mobile agent and CoA. Registration with HA. Binding update (HoA -> CoA). Communicating with MN: use HoA. HA forwards packet from HoA to CoA. CMPE 257 Winter'11 15
Discovering Agents Agents periodically beacon advertisements CMPE 257 Winter'11 16
Agent Discovery Agent advertisement (beaconing): Mobile agent broadcast agent advertisement at regular intervals ( I am here ). Agent solicitation: MH can poll ( anyone here? ). Mobile agent responds to poll. CMPE 257 Winter'11 17
Discovering Agents MH polls; agent responds. CMPE 257 Winter'11 18
Agent Advertisement Follows ICMP router advertisement message. List one or more available care-of addresses. Inform the MN about special features provided by FA. Example: Alternative encapsulation techniques, header compression. CMPE 257 Winter'11 19
Registration CMPE 257 Winter'11 20
Registering When away, MH registers its CoA with HA (binding update). Binding: (HoA->CoA) Binding has a lifetime. CMPE 257 Winter'11 21
Registration Process MH sends a registration request with CoA. HA authenticates request. HA approves or disapproves the request. HA adds necessary information to its routing table. HA sends registration reply back to MH. CMPE 257 Winter'11 22
Registration Process (cont d ) In the case of FA-based CoA: FA is involved in registration. FA is also involved in packet forwarding. Encapsulation. Tunneling. CMPE 257 Winter'11 23
Tunneling HA tunnels datagrams destined to MN when MN is away. Datagrams sent to MH directly. Or sent to FA which forwards to MN s CoA. Tunnel terminates at MH s CoA (either the MH or the FA). CMPE 257 Winter'11 24
Tunneling SRC Tunneled Data Packet HA keeps binding between MH and CoA CMPE 257 Winter'11 25
Encapsulation Tunneling requires encapsulation. Sending the original packet (CH->MH) in another packet (HA->CoA). Default encapsulation mechanism: IP-within-IP (tunnel). Tunnel header: new IP header inserted by the tunnel source (home agent). Destination IP: CoA CMPE 257 Winter'11 26
Tunneling in Mobile IP CMPE 257 Winter'11 27
The Triangle Routing Problem Aka, dogleg routing. MH->CH: direct. CH->MH: CH->HA->MH Inefficient Solution: route optimization. Deliver binding updates directly to CH. CMPE 257 Winter'11 28
Route Optimization Binding caches: Nodes can keep caches with CoA for MHs. If node has entry for MH, sends data directly. Otherwise, triangulates with HA. Binding cache entries have TTL. HA, FA, or MH can send binding cache updates to CH. CMPE 257 Winter'11 29
Simultaneous Bindings MN can register multiple CoA swith HA. Why? De-registration. Explicit. Implicit. CMPE 257 Winter'11 30
Handoffs MH moving among FN. New CoA registered with HA. Previous FA not necessarily notified. Old registration will expire. New data delivered to new CoA. In-flight data? Dropped and retransmitted by upper layers, or FA notified of new CoA; FA forwards data to new CoA. CMPE 257 Winter'11 31
Types of Handoffs MN-initiated: Handoff managed by MN. MN measures signal strength to AP. Decides target AP and switchs over. Network-initiated: APs decide when to hand over and to whom. CMPE 257 Winter'11 32
Handoff Signaling Forward handoff: Target AP contacts current AP to initiate handoff. Backward handoff: Current AP contacts the target AP. CMPE 257 Winter'11 33
Handoff Delay 3 components: Detect need of handoff. Link establishment between MN and new AP. Registration with HA. Pre- and post-registration handoffs: Pre-registration registers MN with HA before handoff. Post-registration: HA registration happens after handoff. CMPE 257 Winter'11 34
Authentication Malicious nodes can infiltrate FNs. Mobile IP registration includes authentication info exchange. MH-HA. MH-FA. HA-FA. Protection against replay attacks. Timestamp and nonces. CMPE 257 Winter'11 35
Mobility Support in IPv6 Route optimization is default. Fields for specifying both CoA and permanent IP address. No need for encapsulation. CMPE 257 Winter'11 36
TCP Performance in Mobile-IP (Choong) Source of overhead: triangle routing. Additional processing at HA and FA. Additional delay due to triangulation. Additional delay due to fragmentation (extra IP header). Handoffs. CMPE 257 Winter'11 37
Goal Determine the impact on TCP performance of Combined overhead sources. Individual overhead sources. CMPE 257 Winter'11 38
Methodology Several scenarios that compound or isolate overhead sources. Compare performance of between scenario pairs. FTP transfer btween MH and CH. Metric: TCP throughput. CMPE 257 Winter'11 39
Summary of Results Dogleg routing as main cause of TCP throughput degradation. Solution: route optimization. Handoff is second. Mobile-IP s inherent delay in re-establish connectivity with new FA. Solutions: Increase frequency of router advertisements. Use link-layer information to trigger handoff. CMPE 257 Winter'11 40
FLIP: Flexible Interconnection Protocol Ignacio Solis Katia Obraczka CMPE 257 Winter'11 41
Overview FLIP overview Why FLIP? Motivation FLIP headers FLIP packets Comparison with IP Comparison with Directed Diffusion Conclusions CMPE 257 Winter'11 42
What is FLIP? FLIP is a network protocol that aims to be flexible. It tries to reduce the overhead as much as possible for small devices but does not limit the functionality of more powerful ones. Configurable by higher layers (Header morphing) CMPE 257 Winter'11 43
Why FLIP? Generic protocols have too much overhead for small devices. Specific protocols are not general enough. Applications need access to the lower layers to optimize use. Every bit counts CMPE 257 Winter'11 44
Sensor Networks Data gathering Small power constrained devices Wireless communication Long Lifetime Large Scale Specific Tasks Unattended CMPE 257 Winter'11 45
What about IP? Overhead Addressing scheme? Routing? Fragmentation? Size? etc. CMPE 257 Winter'11 46
Fields defined by FLIP Version (1 byte) Destination (2, 4 or 16 bytes) Source (2, 4 or 16 bytes) Length (2 bytes) Time To Live (1 byte) Flow (4 bytes) Protocol (1 byte) Checksum (2 bytes) CMPE 257 Winter'11 47
The Meta-Header Bitmap The meta-header bit map defines which fields will be included in the header. Each header field will be represented by one or more bits in the meta-header. If the bit is on, the field will appear. CMPE 257 Winter'11 48
The continuation bit We don't really need the whole metaheader bitmap since not all fields might be required. The bitmap is divided in groups which are then placed on different bytes. CMPE 257 Winter'11 49
The ESP packet Extra-Small-Packet For special very small payloads (6 or 14 bits) CMPE 257 Winter'11 50
Current Work on FLIP FLIP Header GTP Header GTP flags CMPE 257 Winter'11 51
Sample FLIP Packets FLIP ESP packet (extra simple packet) FLIP/GTP packet CMPE 257 Winter'11 52
Sample API Uses standard socket interface CMPE 257 Winter'11 53
FLIP Functions CMPE 257 Winter'11 54
Comparison with IP Packet sizes for 1 and 1000 byte payloads The special cases of Destination and Source and Destination only use 2 byte addresses. Percentages are overhead of header compared to data. CMPE 257 Winter'11 55
1 0 0. 0 % 5 0. 0 % 0. 0 % 1 0 0 0 b y t e p a y l o a d H e a d e r O v e r h e a d 9 8. 0 % 9 7. 9 % I P v 4 F L I P ( I P v 4 ) 9 6. 2 % 9 5. 9 % I P v 6 F L I P ( I P v 6 ) F L I P ( D + S ) F L I P ( D ) H e a d e r 75.0% 9 9. 0 % 9 9. 7 % Data 25.0% CMPE 257 Winter'11 56
1 0 0. 0 % 5 0. 0 % 0. 0 % 1 b y t e p a y l o a d H e a d e r O v e r h e a d 4. 8 % 4. 5 % 9 5. 2 % 9 5. 5 % I P v 4 F L I P ( I P v 4 ) 2. 4 % 2. 3 % I P v 6 F L I P ( I P v 6 ) 9. 1 % 9 0. 9 % F L I P ( D + S ) 2 5. 0 % 7 5. 0 % F L I P ( D ) H e a d e r 75.0% 9 7. 6 % 9 7. 7 % Data 25.0% CMPE 257 Winter'11 57
Directed Diffusion Sink node collects data Sink floods an interest to the whole network, establishing reverse paths to itself. Nodes that have the data the sink is interested in report back (multiple-paths). Sink reinforces the best path, that is, requests a higher data rate on that path. The interest is flooded periodically Newer versions of Directed Diffusion have other mechanisms CMPE 257 Winter'11 58
Scenario 1: Diffusion Packets Can we optimize Diffusion by using FLIP? Flexible Header Diffusion Static Header CMPE 257 Winter'11 59
Diffusion Monitoring CMPE 257 Winter'11 60
Scenario 2: Simple Data Gathering CMPE 257 Winter'11 61
Simulation Parameters NS-2, 2000m x 2000m area, 10 runs, 21 secs. 300 nodes, no movement. 250m transmission range. 802.11-like MAC. 660 mw / 395 mw Starting energy is 1 Joule Interests are every 5 seconds 1 source, 1 sink requesting 10pkts/sec CMPE 257 Winter'11 62
Simple Data Gathering CMPE 257 Winter'11 63
Adding Data Aggregation Aggregate data as it flows through the network Data must meet certain criteria Not all data can be aggregated Lossy & lossless aggregation CMPE 257 Winter'11 64
Scenario 3: Ring Aggregation CMPE 257 Winter'11 65
Conclusions FLIP incurs in small overhead when providing IP functionality. Header overhead on special cases can be very small. For example on very small payloads. It does not try to replace protocols such as IP. More research is needed since many variables are yet to be determined. CMPE 257 Winter'11 66